Merging upstream version 1.44.3.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2571 insertions, 0 deletions

diff --git a/fluent-bit/lib/luajit-3065c9/src/lj_asm.c b/fluent-bit/lib/luajit-3065c9/src/lj_asm.c
new file mode 100644
index 000000000..6f5e0c45b
--- /dev/null
+++ b/fluent-bit/lib/luajit-3065c9/src/lj_asm.c
@@ -0,0 +1,2571 @@
+/*
+** IR assembler (SSA IR -> machine code).
+** Copyright (C) 2005-2022 Mike Pall. See Copyright Notice in luajit.h
+*/
+
+#define lj_asm_c
+#define LUA_CORE
+
+#include "lj_obj.h"
+
+#if LJ_HASJIT
+
+#include "lj_gc.h"
+#include "lj_buf.h"
+#include "lj_str.h"
+#include "lj_tab.h"
+#include "lj_frame.h"
+#if LJ_HASFFI
+#include "lj_ctype.h"
+#endif
+#include "lj_ir.h"
+#include "lj_jit.h"
+#include "lj_ircall.h"
+#include "lj_iropt.h"
+#include "lj_mcode.h"
+#include "lj_trace.h"
+#include "lj_snap.h"
+#include "lj_asm.h"
+#include "lj_dispatch.h"
+#include "lj_vm.h"
+#include "lj_target.h"
+
+#ifdef LUA_USE_ASSERT
+#include <stdio.h>
+#endif
+
+/* -- Assembler state and common macros ----------------------------------- */
+
+/* Assembler state. */
+typedef struct ASMState {
+  RegCost cost[RID_MAX];  /* Reference and blended allocation cost for regs. */
+
+  MCode *mcp;		/* Current MCode pointer (grows down). */
+  MCode *mclim;		/* Lower limit for MCode memory + red zone. */
+#ifdef LUA_USE_ASSERT
+  MCode *mcp_prev;	/* Red zone overflow check. */
+#endif
+
+  IRIns *ir;		/* Copy of pointer to IR instructions/constants. */
+  jit_State *J;		/* JIT compiler state. */
+
+#if LJ_TARGET_X86ORX64
+  x86ModRM mrm;		/* Fused x86 address operand. */
+#endif
+
+  RegSet freeset;	/* Set of free registers. */
+  RegSet modset;	/* Set of registers modified inside the loop. */
+  RegSet weakset;	/* Set of weakly referenced registers. */
+  RegSet phiset;	/* Set of PHI registers. */
+
+  uint32_t flags;	/* Copy of JIT compiler flags. */
+  int loopinv;		/* Loop branch inversion (0:no, 1:yes, 2:yes+CC_P). */
+
+  int32_t evenspill;	/* Next even spill slot. */
+  int32_t oddspill;	/* Next odd spill slot (or 0). */
+
+  IRRef curins;		/* Reference of current instruction. */
+  IRRef stopins;	/* Stop assembly before hitting this instruction. */
+  IRRef orignins;	/* Original T->nins. */
+
+  IRRef snapref;	/* Current snapshot is active after this reference. */
+  IRRef snaprename;	/* Rename highwater mark for snapshot check. */
+  SnapNo snapno;	/* Current snapshot number. */
+  SnapNo loopsnapno;	/* Loop snapshot number. */
+  int snapalloc;	/* Current snapshot needs allocation. */
+  BloomFilter snapfilt1, snapfilt2;	/* Filled with snapshot refs. */
+
+  IRRef fuseref;	/* Fusion limit (loopref, 0 or FUSE_DISABLED). */
+  IRRef sectref;	/* Section base reference (loopref or 0). */
+  IRRef loopref;	/* Reference of LOOP instruction (or 0). */
+
+  BCReg topslot;	/* Number of slots for stack check (unless 0). */
+  int32_t gcsteps;	/* Accumulated number of GC steps (per section). */
+
+  GCtrace *T;		/* Trace to assemble. */
+  GCtrace *parent;	/* Parent trace (or NULL). */
+
+  MCode *mcbot;		/* Bottom of reserved MCode. */
+  MCode *mctop;		/* Top of generated MCode. */
+  MCode *mctoporig;	/* Original top of generated MCode. */
+  MCode *mcloop;	/* Pointer to loop MCode (or NULL). */
+  MCode *invmcp;	/* Points to invertible loop branch (or NULL). */
+  MCode *flagmcp;	/* Pending opportunity to merge flag setting ins. */
+  MCode *realign;	/* Realign loop if not NULL. */
+
+#ifdef RID_NUM_KREF
+  intptr_t krefk[RID_NUM_KREF];
+#endif
+  IRRef1 phireg[RID_MAX];  /* PHI register references. */
+  uint16_t parentmap[LJ_MAX_JSLOTS];  /* Parent instruction to RegSP map. */
+} ASMState;
+
+#ifdef LUA_USE_ASSERT
+#define lj_assertA(c, ...)	lj_assertG_(J2G(as->J), (c), __VA_ARGS__)
+#else
+#define lj_assertA(c, ...)	((void)as)
+#endif
+
+#define IR(ref)			(&as->ir[(ref)])
+
+#define ASMREF_TMP1		REF_TRUE	/* Temp. register. */
+#define ASMREF_TMP2		REF_FALSE	/* Temp. register. */
+#define ASMREF_L		REF_NIL		/* Stores register for L. */
+
+/* Check for variant to invariant references. */
+#define iscrossref(as, ref)	((ref) < as->sectref)
+
+/* Inhibit memory op fusion from variant to invariant references. */
+#define FUSE_DISABLED		(~(IRRef)0)
+#define mayfuse(as, ref)	((ref) > as->fuseref)
+#define neverfuse(as)		(as->fuseref == FUSE_DISABLED)
+#define canfuse(as, ir)		(!neverfuse(as) && !irt_isphi((ir)->t))
+#define opisfusableload(o) \
+  ((o) == IR_ALOAD || (o) == IR_HLOAD || (o) == IR_ULOAD || \
+   (o) == IR_FLOAD || (o) == IR_XLOAD || (o) == IR_SLOAD || (o) == IR_VLOAD)
+
+/* Sparse limit checks using a red zone before the actual limit. */
+#define MCLIM_REDZONE	64
+
+static LJ_NORET LJ_NOINLINE void asm_mclimit(ASMState *as)
+{
+  lj_mcode_limiterr(as->J, (size_t)(as->mctop - as->mcp + 4*MCLIM_REDZONE));
+}
+
+static LJ_AINLINE void checkmclim(ASMState *as)
+{
+#ifdef LUA_USE_ASSERT
+  if (as->mcp + MCLIM_REDZONE < as->mcp_prev) {
+    IRIns *ir = IR(as->curins+1);
+    lj_assertA(0, "red zone overflow: %p IR %04d  %02d %04d %04d\n", as->mcp,
+      as->curins+1-REF_BIAS, ir->o, ir->op1-REF_BIAS, ir->op2-REF_BIAS);
+  }
+#endif
+  if (LJ_UNLIKELY(as->mcp < as->mclim)) asm_mclimit(as);
+#ifdef LUA_USE_ASSERT
+  as->mcp_prev = as->mcp;
+#endif
+}
+
+#ifdef RID_NUM_KREF
+#define ra_iskref(ref)		((ref) < RID_NUM_KREF)
+#define ra_krefreg(ref)		((Reg)(RID_MIN_KREF + (Reg)(ref)))
+#define ra_krefk(as, ref)	(as->krefk[(ref)])
+
+static LJ_AINLINE void ra_setkref(ASMState *as, Reg r, intptr_t k)
+{
+  IRRef ref = (IRRef)(r - RID_MIN_KREF);
+  as->krefk[ref] = k;
+  as->cost[r] = REGCOST(ref, ref);
+}
+
+#else
+#define ra_iskref(ref)		0
+#define ra_krefreg(ref)		RID_MIN_GPR
+#define ra_krefk(as, ref)	0
+#endif
+
+/* Arch-specific field offsets. */
+static const uint8_t field_ofs[IRFL__MAX+1] = {
+#define FLOFS(name, ofs)	(uint8_t)(ofs),
+IRFLDEF(FLOFS)
+#undef FLOFS
+  0
+};
+
+/* -- Target-specific instruction emitter --------------------------------- */
+
+#if LJ_TARGET_X86ORX64
+#include "lj_emit_x86.h"
+#elif LJ_TARGET_ARM
+#include "lj_emit_arm.h"
+#elif LJ_TARGET_ARM64
+#include "lj_emit_arm64.h"
+#elif LJ_TARGET_PPC
+#include "lj_emit_ppc.h"
+#elif LJ_TARGET_MIPS
+#include "lj_emit_mips.h"
+#else
+#error "Missing instruction emitter for target CPU"
+#endif
+
+/* Generic load/store of register from/to stack slot. */
+#define emit_spload(as, ir, r, ofs) \
+  emit_loadofs(as, ir, (r), RID_SP, (ofs))
+#define emit_spstore(as, ir, r, ofs) \
+  emit_storeofs(as, ir, (r), RID_SP, (ofs))
+
+/* -- Register allocator debugging ---------------------------------------- */
+
+/* #define LUAJIT_DEBUG_RA */
+
+#ifdef LUAJIT_DEBUG_RA
+
+#include <stdio.h>
+#include <stdarg.h>
+
+#define RIDNAME(name)	#name,
+static const char *const ra_regname[] = {
+  GPRDEF(RIDNAME)
+  FPRDEF(RIDNAME)
+  VRIDDEF(RIDNAME)
+  NULL
+};
+#undef RIDNAME
+
+static char ra_dbg_buf[65536];
+static char *ra_dbg_p;
+static char *ra_dbg_merge;
+static MCode *ra_dbg_mcp;
+
+static void ra_dstart(void)
+{
+  ra_dbg_p = ra_dbg_buf;
+  ra_dbg_merge = NULL;
+  ra_dbg_mcp = NULL;
+}
+
+static void ra_dflush(void)
+{
+  fwrite(ra_dbg_buf, 1, (size_t)(ra_dbg_p-ra_dbg_buf), stdout);
+  ra_dstart();
+}
+
+static void ra_dprintf(ASMState *as, const char *fmt, ...)
+{
+  char *p;
+  va_list argp;
+  va_start(argp, fmt);
+  p = ra_dbg_mcp == as->mcp ? ra_dbg_merge : ra_dbg_p;
+  ra_dbg_mcp = NULL;
+  p += sprintf(p, "%08x  \e[36m%04d ", (uintptr_t)as->mcp, as->curins-REF_BIAS);
+  for (;;) {
+    const char *e = strchr(fmt, '$');
+    if (e == NULL) break;
+    memcpy(p, fmt, (size_t)(e-fmt));
+    p += e-fmt;
+    if (e[1] == 'r') {
+      Reg r = va_arg(argp, Reg) & RID_MASK;
+      if (r <= RID_MAX) {
+	const char *q;
+	for (q = ra_regname[r]; *q; q++)
+	  *p++ = *q >= 'A' && *q <= 'Z' ? *q + 0x20 : *q;
+      } else {
+	*p++ = '?';
+	lj_assertA(0, "bad register %d for debug format \"%s\"", r, fmt);
+      }
+    } else if (e[1] == 'f' || e[1] == 'i') {
+      IRRef ref;
+      if (e[1] == 'f')
+	ref = va_arg(argp, IRRef);
+      else
+	ref = va_arg(argp, IRIns *) - as->ir;
+      if (ref >= REF_BIAS)
+	p += sprintf(p, "%04d", ref - REF_BIAS);
+      else
+	p += sprintf(p, "K%03d", REF_BIAS - ref);
+    } else if (e[1] == 's') {
+      uint32_t slot = va_arg(argp, uint32_t);
+      p += sprintf(p, "[sp+0x%x]", sps_scale(slot));
+    } else if (e[1] == 'x') {
+      p += sprintf(p, "%08x", va_arg(argp, int32_t));
+    } else {
+      lj_assertA(0, "bad debug format code");
+    }
+    fmt = e+2;
+  }
+  va_end(argp);
+  while (*fmt)
+    *p++ = *fmt++;
+  *p++ = '\e'; *p++ = '['; *p++ = 'm'; *p++ = '\n';
+  if (p > ra_dbg_buf+sizeof(ra_dbg_buf)-256) {
+    fwrite(ra_dbg_buf, 1, (size_t)(p-ra_dbg_buf), stdout);
+    p = ra_dbg_buf;
+  }
+  ra_dbg_p = p;
+}
+
+#define RA_DBG_START()	ra_dstart()
+#define RA_DBG_FLUSH()	ra_dflush()
+#define RA_DBG_REF() \
+  do { char *_p = ra_dbg_p; ra_dprintf(as, ""); \
+       ra_dbg_merge = _p; ra_dbg_mcp = as->mcp; } while (0)
+#define RA_DBGX(x)	ra_dprintf x
+
+#else
+#define RA_DBG_START()	((void)0)
+#define RA_DBG_FLUSH()	((void)0)
+#define RA_DBG_REF()	((void)0)
+#define RA_DBGX(x)	((void)0)
+#endif
+
+/* -- Register allocator -------------------------------------------------- */
+
+#define ra_free(as, r)		rset_set(as->freeset, (r))
+#define ra_modified(as, r)	rset_set(as->modset, (r))
+#define ra_weak(as, r)		rset_set(as->weakset, (r))
+#define ra_noweak(as, r)	rset_clear(as->weakset, (r))
+
+#define ra_used(ir)		(ra_hasreg((ir)->r) || ra_hasspill((ir)->s))
+
+/* Setup register allocator. */
+static void ra_setup(ASMState *as)
+{
+  Reg r;
+  /* Initially all regs (except the stack pointer) are free for use. */
+  as->freeset = RSET_INIT;
+  as->modset = RSET_EMPTY;
+  as->weakset = RSET_EMPTY;
+  as->phiset = RSET_EMPTY;
+  memset(as->phireg, 0, sizeof(as->phireg));
+  for (r = RID_MIN_GPR; r < RID_MAX; r++)
+    as->cost[r] = REGCOST(~0u, 0u);
+}
+
+/* Rematerialize constants. */
+static Reg ra_rematk(ASMState *as, IRRef ref)
+{
+  IRIns *ir;
+  Reg r;
+  if (ra_iskref(ref)) {
+    r = ra_krefreg(ref);
+    lj_assertA(!rset_test(as->freeset, r), "rematk of free reg %d", r);
+    ra_free(as, r);
+    ra_modified(as, r);
+#if LJ_64
+    emit_loadu64(as, r, ra_krefk(as, ref));
+#else
+    emit_loadi(as, r, ra_krefk(as, ref));
+#endif
+    return r;
+  }
+  ir = IR(ref);
+  r = ir->r;
+  lj_assertA(ra_hasreg(r), "rematk of K%03d has no reg", REF_BIAS - ref);
+  lj_assertA(!ra_hasspill(ir->s),
+	     "rematk of K%03d has spill slot [%x]", REF_BIAS - ref, ir->s);
+  ra_free(as, r);
+  ra_modified(as, r);
+  ir->r = RID_INIT;  /* Do not keep any hint. */
+  RA_DBGX((as, "remat     $i $r", ir, r));
+#if !LJ_SOFTFP32
+  if (ir->o == IR_KNUM) {
+    emit_loadk64(as, r, ir);
+  } else
+#endif
+  if (emit_canremat(REF_BASE) && ir->o == IR_BASE) {
+    ra_sethint(ir->r, RID_BASE);  /* Restore BASE register hint. */
+    emit_getgl(as, r, jit_base);
+  } else if (emit_canremat(ASMREF_L) && ir->o == IR_KPRI) {
+    /* REF_NIL stores ASMREF_L register. */
+    lj_assertA(irt_isnil(ir->t), "rematk of bad ASMREF_L");
+    emit_getgl(as, r, cur_L);
+#if LJ_64
+  } else if (ir->o == IR_KINT64) {
+    emit_loadu64(as, r, ir_kint64(ir)->u64);
+#if LJ_GC64
+  } else if (ir->o == IR_KGC) {
+    emit_loadu64(as, r, (uintptr_t)ir_kgc(ir));
+  } else if (ir->o == IR_KPTR || ir->o == IR_KKPTR) {
+    emit_loadu64(as, r, (uintptr_t)ir_kptr(ir));
+#endif
+#endif
+  } else {
+    lj_assertA(ir->o == IR_KINT || ir->o == IR_KGC ||
+	       ir->o == IR_KPTR || ir->o == IR_KKPTR || ir->o == IR_KNULL,
+	       "rematk of bad IR op %d", ir->o);
+    emit_loadi(as, r, ir->i);
+  }
+  return r;
+}
+
+/* Force a spill. Allocate a new spill slot if needed. */
+static int32_t ra_spill(ASMState *as, IRIns *ir)
+{
+  int32_t slot = ir->s;
+  lj_assertA(ir >= as->ir + REF_TRUE,
+	     "spill of K%03d", REF_BIAS - (int)(ir - as->ir));
+  if (!ra_hasspill(slot)) {
+    if (irt_is64(ir->t)) {
+      slot = as->evenspill;
+      as->evenspill += 2;
+    } else if (as->oddspill) {
+      slot = as->oddspill;
+      as->oddspill = 0;
+    } else {
+      slot = as->evenspill;
+      as->oddspill = slot+1;
+      as->evenspill += 2;
+    }
+    if (as->evenspill > 256)
+      lj_trace_err(as->J, LJ_TRERR_SPILLOV);
+    ir->s = (uint8_t)slot;
+  }
+  return sps_scale(slot);
+}
+
+/* Release the temporarily allocated register in ASMREF_TMP1/ASMREF_TMP2. */
+static Reg ra_releasetmp(ASMState *as, IRRef ref)
+{
+  IRIns *ir = IR(ref);
+  Reg r = ir->r;
+  lj_assertA(ra_hasreg(r), "release of TMP%d has no reg", ref-ASMREF_TMP1+1);
+  lj_assertA(!ra_hasspill(ir->s),
+	     "release of TMP%d has spill slot [%x]", ref-ASMREF_TMP1+1, ir->s);
+  ra_free(as, r);
+  ra_modified(as, r);
+  ir->r = RID_INIT;
+  return r;
+}
+
+/* Restore a register (marked as free). Rematerialize or force a spill. */
+static Reg ra_restore(ASMState *as, IRRef ref)
+{
+  if (emit_canremat(ref)) {
+    return ra_rematk(as, ref);
+  } else {
+    IRIns *ir = IR(ref);
+    int32_t ofs = ra_spill(as, ir);  /* Force a spill slot. */
+    Reg r = ir->r;
+    lj_assertA(ra_hasreg(r), "restore of IR %04d has no reg", ref - REF_BIAS);
+    ra_sethint(ir->r, r);  /* Keep hint. */
+    ra_free(as, r);
+    if (!rset_test(as->weakset, r)) {  /* Only restore non-weak references. */
+      ra_modified(as, r);
+      RA_DBGX((as, "restore   $i $r", ir, r));
+      emit_spload(as, ir, r, ofs);
+    }
+    return r;
+  }
+}
+
+/* Save a register to a spill slot. */
+static void ra_save(ASMState *as, IRIns *ir, Reg r)
+{
+  RA_DBGX((as, "save      $i $r", ir, r));
+  emit_spstore(as, ir, r, sps_scale(ir->s));
+}
+
+#define MINCOST(name) \
+  if (rset_test(RSET_ALL, RID_##name) && \
+      LJ_LIKELY(allow&RID2RSET(RID_##name)) && as->cost[RID_##name] < cost) \
+    cost = as->cost[RID_##name];
+
+/* Evict the register with the lowest cost, forcing a restore. */
+static Reg ra_evict(ASMState *as, RegSet allow)
+{
+  IRRef ref;
+  RegCost cost = ~(RegCost)0;
+  lj_assertA(allow != RSET_EMPTY, "evict from empty set");
+  if (RID_NUM_FPR == 0 || allow < RID2RSET(RID_MAX_GPR)) {
+    GPRDEF(MINCOST)
+  } else {
+    FPRDEF(MINCOST)
+  }
+  ref = regcost_ref(cost);
+  lj_assertA(ra_iskref(ref) || (ref >= as->T->nk && ref < as->T->nins),
+	     "evict of out-of-range IR %04d", ref - REF_BIAS);
+  /* Preferably pick any weak ref instead of a non-weak, non-const ref. */
+  if (!irref_isk(ref) && (as->weakset & allow)) {
+    IRIns *ir = IR(ref);
+    if (!rset_test(as->weakset, ir->r))
+      ref = regcost_ref(as->cost[rset_pickbot((as->weakset & allow))]);
+  }
+  return ra_restore(as, ref);
+}
+
+/* Pick any register (marked as free). Evict on-demand. */
+static Reg ra_pick(ASMState *as, RegSet allow)
+{
+  RegSet pick = as->freeset & allow;
+  if (!pick)
+    return ra_evict(as, allow);
+  else
+    return rset_picktop(pick);
+}
+
+/* Get a scratch register (marked as free). */
+static Reg ra_scratch(ASMState *as, RegSet allow)
+{
+  Reg r = ra_pick(as, allow);
+  ra_modified(as, r);
+  RA_DBGX((as, "scratch        $r", r));
+  return r;
+}
+
+/* Evict all registers from a set (if not free). */
+static void ra_evictset(ASMState *as, RegSet drop)
+{
+  RegSet work;
+  as->modset |= drop;
+#if !LJ_SOFTFP
+  work = (drop & ~as->freeset) & RSET_FPR;
+  while (work) {
+    Reg r = rset_pickbot(work);
+    ra_restore(as, regcost_ref(as->cost[r]));
+    rset_clear(work, r);
+    checkmclim(as);
+  }
+#endif
+  work = (drop & ~as->freeset);
+  while (work) {
+    Reg r = rset_pickbot(work);
+    ra_restore(as, regcost_ref(as->cost[r]));
+    rset_clear(work, r);
+    checkmclim(as);
+  }
+}
+
+/* Evict (rematerialize) all registers allocated to constants. */
+static void ra_evictk(ASMState *as)
+{
+  RegSet work;
+#if !LJ_SOFTFP
+  work = ~as->freeset & RSET_FPR;
+  while (work) {
+    Reg r = rset_pickbot(work);
+    IRRef ref = regcost_ref(as->cost[r]);
+    if (emit_canremat(ref) && irref_isk(ref)) {
+      ra_rematk(as, ref);
+      checkmclim(as);
+    }
+    rset_clear(work, r);
+  }
+#endif
+  work = ~as->freeset & RSET_GPR;
+  while (work) {
+    Reg r = rset_pickbot(work);
+    IRRef ref = regcost_ref(as->cost[r]);
+    if (emit_canremat(ref) && irref_isk(ref)) {
+      ra_rematk(as, ref);
+      checkmclim(as);
+    }
+    rset_clear(work, r);
+  }
+}
+
+#ifdef RID_NUM_KREF
+/* Allocate a register for a constant. */
+static Reg ra_allock(ASMState *as, intptr_t k, RegSet allow)
+{
+  /* First try to find a register which already holds the same constant. */
+  RegSet pick, work = ~as->freeset & RSET_GPR;
+  Reg r;
+  while (work) {
+    IRRef ref;
+    r = rset_pickbot(work);
+    ref = regcost_ref(as->cost[r]);
+#if LJ_64
+    if (ref < ASMREF_L) {
+      if (ra_iskref(ref)) {
+	if (k == ra_krefk(as, ref))
+	  return r;
+      } else {
+	IRIns *ir = IR(ref);
+	if ((ir->o == IR_KINT64 && k == (int64_t)ir_kint64(ir)->u64) ||
+#if LJ_GC64
+	    (ir->o == IR_KINT && k == ir->i) ||
+	    (ir->o == IR_KGC && k == (intptr_t)ir_kgc(ir)) ||
+	    ((ir->o == IR_KPTR || ir->o == IR_KKPTR) &&
+	     k == (intptr_t)ir_kptr(ir))
+#else
+	    (ir->o != IR_KINT64 && k == ir->i)
+#endif
+	   )
+	  return r;
+      }
+    }
+#else
+    if (ref < ASMREF_L &&
+	k == (ra_iskref(ref) ? ra_krefk(as, ref) : IR(ref)->i))
+      return r;
+#endif
+    rset_clear(work, r);
+  }
+  pick = as->freeset & allow;
+  if (pick) {
+    /* Constants should preferably get unmodified registers. */
+    if ((pick & ~as->modset))
+      pick &= ~as->modset;
+    r = rset_pickbot(pick);  /* Reduce conflicts with inverse allocation. */
+  } else {
+    r = ra_evict(as, allow);
+  }
+  RA_DBGX((as, "allock    $x $r", k, r));
+  ra_setkref(as, r, k);
+  rset_clear(as->freeset, r);
+  ra_noweak(as, r);
+  return r;
+}
+
+/* Allocate a specific register for a constant. */
+static void ra_allockreg(ASMState *as, intptr_t k, Reg r)
+{
+  Reg kr = ra_allock(as, k, RID2RSET(r));
+  if (kr != r) {
+    IRIns irdummy;
+    irdummy.t.irt = IRT_INT;
+    ra_scratch(as, RID2RSET(r));
+    emit_movrr(as, &irdummy, r, kr);
+  }
+}
+#else
+#define ra_allockreg(as, k, r)		emit_loadi(as, (r), (k))
+#endif
+
+/* Allocate a register for ref from the allowed set of registers.
+** Note: this function assumes the ref does NOT have a register yet!
+** Picks an optimal register, sets the cost and marks the register as non-free.
+*/
+static Reg ra_allocref(ASMState *as, IRRef ref, RegSet allow)
+{
+  IRIns *ir = IR(ref);
+  RegSet pick = as->freeset & allow;
+  Reg r;
+  lj_assertA(ra_noreg(ir->r),
+	     "IR %04d already has reg %d", ref - REF_BIAS, ir->r);
+  if (pick) {
+    /* First check register hint from propagation or PHI. */
+    if (ra_hashint(ir->r)) {
+      r = ra_gethint(ir->r);
+      if (rset_test(pick, r))  /* Use hint register if possible. */
+	goto found;
+      /* Rematerialization is cheaper than missing a hint. */
+      if (rset_test(allow, r) && emit_canremat(regcost_ref(as->cost[r]))) {
+	ra_rematk(as, regcost_ref(as->cost[r]));
+	goto found;
+      }
+      RA_DBGX((as, "hintmiss  $f $r", ref, r));
+    }
+    /* Invariants should preferably get unmodified registers. */
+    if (ref < as->loopref && !irt_isphi(ir->t)) {
+      if ((pick & ~as->modset))
+	pick &= ~as->modset;
+      r = rset_pickbot(pick);  /* Reduce conflicts with inverse allocation. */
+    } else {
+      /* We've got plenty of regs, so get callee-save regs if possible. */
+      if (RID_NUM_GPR > 8 && (pick & ~RSET_SCRATCH))
+	pick &= ~RSET_SCRATCH;
+      r = rset_picktop(pick);
+    }
+  } else {
+    r = ra_evict(as, allow);
+  }
+found:
+  RA_DBGX((as, "alloc     $f $r", ref, r));
+  ir->r = (uint8_t)r;
+  rset_clear(as->freeset, r);
+  ra_noweak(as, r);
+  as->cost[r] = REGCOST_REF_T(ref, irt_t(ir->t));
+  return r;
+}
+
+/* Allocate a register on-demand. */
+static Reg ra_alloc1(ASMState *as, IRRef ref, RegSet allow)
+{
+  Reg r = IR(ref)->r;
+  /* Note: allow is ignored if the register is already allocated. */
+  if (ra_noreg(r)) r = ra_allocref(as, ref, allow);
+  ra_noweak(as, r);
+  return r;
+}
+
+/* Add a register rename to the IR. */
+static void ra_addrename(ASMState *as, Reg down, IRRef ref, SnapNo snapno)
+{
+  IRRef ren;
+  lj_ir_set(as->J, IRT(IR_RENAME, IRT_NIL), ref, snapno);
+  ren = tref_ref(lj_ir_emit(as->J));
+  as->J->cur.ir[ren].r = (uint8_t)down;
+  as->J->cur.ir[ren].s = SPS_NONE;
+}
+
+/* Rename register allocation and emit move. */
+static void ra_rename(ASMState *as, Reg down, Reg up)
+{
+  IRRef ref = regcost_ref(as->cost[up] = as->cost[down]);
+  IRIns *ir = IR(ref);
+  ir->r = (uint8_t)up;
+  as->cost[down] = 0;
+  lj_assertA((down < RID_MAX_GPR) == (up < RID_MAX_GPR),
+	     "rename between GPR/FPR %d and %d", down, up);
+  lj_assertA(!rset_test(as->freeset, down), "rename from free reg %d", down);
+  lj_assertA(rset_test(as->freeset, up), "rename to non-free reg %d", up);
+  ra_free(as, down);  /* 'down' is free ... */
+  ra_modified(as, down);
+  rset_clear(as->freeset, up);  /* ... and 'up' is now allocated. */
+  ra_noweak(as, up);
+  RA_DBGX((as, "rename    $f $r $r", regcost_ref(as->cost[up]), down, up));
+  emit_movrr(as, ir, down, up);  /* Backwards codegen needs inverse move. */
+  if (!ra_hasspill(IR(ref)->s)) {  /* Add the rename to the IR. */
+    /*
+    ** The rename is effective at the subsequent (already emitted) exit
+    ** branch. This is for the current snapshot (as->snapno). Except if we
+    ** haven't yet allocated any refs for the snapshot (as->snapalloc == 1),
+    ** then it belongs to the next snapshot.
+    ** See also the discussion at asm_snap_checkrename().
+    */
+    ra_addrename(as, down, ref, as->snapno + as->snapalloc);
+  }
+}
+
+/* Pick a destination register (marked as free).
+** Caveat: allow is ignored if there's already a destination register.
+** Use ra_destreg() to get a specific register.
+*/
+static Reg ra_dest(ASMState *as, IRIns *ir, RegSet allow)
+{
+  Reg dest = ir->r;
+  if (ra_hasreg(dest)) {
+    ra_free(as, dest);
+    ra_modified(as, dest);
+  } else {
+    if (ra_hashint(dest) && rset_test((as->freeset&allow), ra_gethint(dest))) {
+      dest = ra_gethint(dest);
+      ra_modified(as, dest);
+      RA_DBGX((as, "dest           $r", dest));
+    } else {
+      dest = ra_scratch(as, allow);
+    }
+    ir->r = dest;
+  }
+  if (LJ_UNLIKELY(ra_hasspill(ir->s))) ra_save(as, ir, dest);
+  return dest;
+}
+
+/* Force a specific destination register (marked as free). */
+static void ra_destreg(ASMState *as, IRIns *ir, Reg r)
+{
+  Reg dest = ra_dest(as, ir, RID2RSET(r));
+  if (dest != r) {
+    lj_assertA(rset_test(as->freeset, r), "dest reg %d is not free", r);
+    ra_modified(as, r);
+    emit_movrr(as, ir, dest, r);
+  }
+}
+
+#if LJ_TARGET_X86ORX64
+/* Propagate dest register to left reference. Emit moves as needed.
+** This is a required fixup step for all 2-operand machine instructions.
+*/
+static void ra_left(ASMState *as, Reg dest, IRRef lref)
+{
+  IRIns *ir = IR(lref);
+  Reg left = ir->r;
+  if (ra_noreg(left)) {
+    if (irref_isk(lref)) {
+      if (ir->o == IR_KNUM) {
+	/* FP remat needs a load except for +0. Still better than eviction. */
+	if (tvispzero(ir_knum(ir)) || !(as->freeset & RSET_FPR)) {
+	  emit_loadk64(as, dest, ir);
+	  return;
+	}
+#if LJ_64
+      } else if (ir->o == IR_KINT64) {
+	emit_loadk64(as, dest, ir);
+	return;
+#if LJ_GC64
+      } else if (ir->o == IR_KGC || ir->o == IR_KPTR || ir->o == IR_KKPTR) {
+	emit_loadk64(as, dest, ir);
+	return;
+#endif
+#endif
+      } else if (ir->o != IR_KPRI) {
+	lj_assertA(ir->o == IR_KINT || ir->o == IR_KGC ||
+		   ir->o == IR_KPTR || ir->o == IR_KKPTR || ir->o == IR_KNULL,
+		   "K%03d has bad IR op %d", REF_BIAS - lref, ir->o);
+	emit_loadi(as, dest, ir->i);
+	return;
+      }
+    }
+    if (!ra_hashint(left) && !iscrossref(as, lref))
+      ra_sethint(ir->r, dest);  /* Propagate register hint. */
+    left = ra_allocref(as, lref, dest < RID_MAX_GPR ? RSET_GPR : RSET_FPR);
+  }
+  ra_noweak(as, left);
+  /* Move needed for true 3-operand instruction: y=a+b ==> y=a; y+=b. */
+  if (dest != left) {
+    /* Use register renaming if dest is the PHI reg. */
+    if (irt_isphi(ir->t) && as->phireg[dest] == lref) {
+      ra_modified(as, left);
+      ra_rename(as, left, dest);
+    } else {
+      emit_movrr(as, ir, dest, left);
+    }
+  }
+}
+#else
+/* Similar to ra_left, except we override any hints. */
+static void ra_leftov(ASMState *as, Reg dest, IRRef lref)
+{
+  IRIns *ir = IR(lref);
+  Reg left = ir->r;
+  if (ra_noreg(left)) {
+    ra_sethint(ir->r, dest);  /* Propagate register hint. */
+    left = ra_allocref(as, lref,
+		       (LJ_SOFTFP || dest < RID_MAX_GPR) ? RSET_GPR : RSET_FPR);
+  }
+  ra_noweak(as, left);
+  if (dest != left) {
+    /* Use register renaming if dest is the PHI reg. */
+    if (irt_isphi(ir->t) && as->phireg[dest] == lref) {
+      ra_modified(as, left);
+      ra_rename(as, left, dest);
+    } else {
+      emit_movrr(as, ir, dest, left);
+    }
+  }
+}
+#endif
+
+/* Force a RID_RETLO/RID_RETHI destination register pair (marked as free). */
+static void ra_destpair(ASMState *as, IRIns *ir)
+{
+  Reg destlo = ir->r, desthi = (ir+1)->r;
+  IRIns *irx = (LJ_64 && !irt_is64(ir->t)) ? ir+1 : ir;
+  /* First spill unrelated refs blocking the destination registers. */
+  if (!rset_test(as->freeset, RID_RETLO) &&
+      destlo != RID_RETLO && desthi != RID_RETLO)
+    ra_restore(as, regcost_ref(as->cost[RID_RETLO]));
+  if (!rset_test(as->freeset, RID_RETHI) &&
+      destlo != RID_RETHI && desthi != RID_RETHI)
+    ra_restore(as, regcost_ref(as->cost[RID_RETHI]));
+  /* Next free the destination registers (if any). */
+  if (ra_hasreg(destlo)) {
+    ra_free(as, destlo);
+    ra_modified(as, destlo);
+  } else {
+    destlo = RID_RETLO;
+  }
+  if (ra_hasreg(desthi)) {
+    ra_free(as, desthi);
+    ra_modified(as, desthi);
+  } else {
+    desthi = RID_RETHI;
+  }
+  /* Check for conflicts and shuffle the registers as needed. */
+  if (destlo == RID_RETHI) {
+    if (desthi == RID_RETLO) {
+#if LJ_TARGET_X86ORX64
+      *--as->mcp = XI_XCHGa + RID_RETHI;
+      if (LJ_64 && irt_is64(irx->t)) *--as->mcp = 0x48;
+#else
+      emit_movrr(as, irx, RID_RETHI, RID_TMP);
+      emit_movrr(as, irx, RID_RETLO, RID_RETHI);
+      emit_movrr(as, irx, RID_TMP, RID_RETLO);
+#endif
+    } else {
+      emit_movrr(as, irx, RID_RETHI, RID_RETLO);
+      if (desthi != RID_RETHI) emit_movrr(as, irx, desthi, RID_RETHI);
+    }
+  } else if (desthi == RID_RETLO) {
+    emit_movrr(as, irx, RID_RETLO, RID_RETHI);
+    if (destlo != RID_RETLO) emit_movrr(as, irx, destlo, RID_RETLO);
+  } else {
+    if (desthi != RID_RETHI) emit_movrr(as, irx, desthi, RID_RETHI);
+    if (destlo != RID_RETLO) emit_movrr(as, irx, destlo, RID_RETLO);
+  }
+  /* Restore spill slots (if any). */
+  if (ra_hasspill((ir+1)->s)) ra_save(as, ir+1, RID_RETHI);
+  if (ra_hasspill(ir->s)) ra_save(as, ir, RID_RETLO);
+}
+
+/* -- Snapshot handling --------- ----------------------------------------- */
+
+/* Can we rematerialize a KNUM instead of forcing a spill? */
+static int asm_snap_canremat(ASMState *as)
+{
+  Reg r;
+  for (r = RID_MIN_FPR; r < RID_MAX_FPR; r++)
+    if (irref_isk(regcost_ref(as->cost[r])))
+      return 1;
+  return 0;
+}
+
+/* Check whether a sunk store corresponds to an allocation. */
+static int asm_sunk_store(ASMState *as, IRIns *ira, IRIns *irs)
+{
+  if (irs->s == 255) {
+    if (irs->o == IR_ASTORE || irs->o == IR_HSTORE ||
+	irs->o == IR_FSTORE || irs->o == IR_XSTORE) {
+      IRIns *irk = IR(irs->op1);
+      if (irk->o == IR_AREF || irk->o == IR_HREFK)
+	irk = IR(irk->op1);
+      return (IR(irk->op1) == ira);
+    }
+    return 0;
+  } else {
+    return (ira + irs->s == irs);  /* Quick check. */
+  }
+}
+
+/* Allocate register or spill slot for a ref that escapes to a snapshot. */
+static void asm_snap_alloc1(ASMState *as, IRRef ref)
+{
+  IRIns *ir = IR(ref);
+  if (!irref_isk(ref) && ir->r != RID_SUNK) {
+    bloomset(as->snapfilt1, ref);
+    bloomset(as->snapfilt2, hashrot(ref, ref + HASH_BIAS));
+    if (ra_used(ir)) return;
+    if (ir->r == RID_SINK) {
+      ir->r = RID_SUNK;
+#if LJ_HASFFI
+      if (ir->o == IR_CNEWI) {  /* Allocate CNEWI value. */
+	asm_snap_alloc1(as, ir->op2);
+	if (LJ_32 && (ir+1)->o == IR_HIOP)
+	  asm_snap_alloc1(as, (ir+1)->op2);
+      } else
+#endif
+      {  /* Allocate stored values for TNEW, TDUP and CNEW. */
+	IRIns *irs;
+	lj_assertA(ir->o == IR_TNEW || ir->o == IR_TDUP || ir->o == IR_CNEW,
+		   "sink of IR %04d has bad op %d", ref - REF_BIAS, ir->o);
+	for (irs = IR(as->snapref-1); irs > ir; irs--)
+	  if (irs->r == RID_SINK && asm_sunk_store(as, ir, irs)) {
+	    lj_assertA(irs->o == IR_ASTORE || irs->o == IR_HSTORE ||
+		       irs->o == IR_FSTORE || irs->o == IR_XSTORE,
+		       "sunk store IR %04d has bad op %d",
+		       (int)(irs - as->ir) - REF_BIAS, irs->o);
+	    asm_snap_alloc1(as, irs->op2);
+	    if (LJ_32 && (irs+1)->o == IR_HIOP)
+	      asm_snap_alloc1(as, (irs+1)->op2);
+	  }
+      }
+    } else {
+      RegSet allow;
+      if (ir->o == IR_CONV && ir->op2 == IRCONV_NUM_INT) {
+	IRIns *irc;
+	for (irc = IR(as->curins); irc > ir; irc--)
+	  if ((irc->op1 == ref || irc->op2 == ref) &&
+	      !(irc->r == RID_SINK || irc->r == RID_SUNK))
+	    goto nosink;  /* Don't sink conversion if result is used. */
+	asm_snap_alloc1(as, ir->op1);
+	return;
+      }
+    nosink:
+      allow = (!LJ_SOFTFP && irt_isfp(ir->t)) ? RSET_FPR : RSET_GPR;
+      if ((as->freeset & allow) ||
+	       (allow == RSET_FPR && asm_snap_canremat(as))) {
+	/* Get a weak register if we have a free one or can rematerialize. */
+	Reg r = ra_allocref(as, ref, allow);  /* Allocate a register. */
+	if (!irt_isphi(ir->t))
+	  ra_weak(as, r);  /* But mark it as weakly referenced. */
+	checkmclim(as);
+	RA_DBGX((as, "snapreg   $f $r", ref, ir->r));
+      } else {
+	ra_spill(as, ir);  /* Otherwise force a spill slot. */
+	RA_DBGX((as, "snapspill $f $s", ref, ir->s));
+      }
+    }
+  }
+}
+
+/* Allocate refs escaping to a snapshot. */
+static void asm_snap_alloc(ASMState *as, int snapno)
+{
+  SnapShot *snap = &as->T->snap[snapno];
+  SnapEntry *map = &as->T->snapmap[snap->mapofs];
+  MSize n, nent = snap->nent;
+  as->snapfilt1 = as->snapfilt2 = 0;
+  for (n = 0; n < nent; n++) {
+    SnapEntry sn = map[n];
+    IRRef ref = snap_ref(sn);
+    if (!irref_isk(ref)) {
+      asm_snap_alloc1(as, ref);
+      if (LJ_SOFTFP && (sn & SNAP_SOFTFPNUM)) {
+	lj_assertA(irt_type(IR(ref+1)->t) == IRT_SOFTFP,
+		   "snap %d[%d] points to bad SOFTFP IR %04d",
+		   snapno, n, ref - REF_BIAS);
+	asm_snap_alloc1(as, ref+1);
+      }
+    }
+  }
+}
+
+/* All guards for a snapshot use the same exitno. This is currently the
+** same as the snapshot number. Since the exact origin of the exit cannot
+** be determined, all guards for the same snapshot must exit with the same
+** RegSP mapping.
+** A renamed ref which has been used in a prior guard for the same snapshot
+** would cause an inconsistency. The easy way out is to force a spill slot.
+*/
+static int asm_snap_checkrename(ASMState *as, IRRef ren)
+{
+  if (bloomtest(as->snapfilt1, ren) &&
+      bloomtest(as->snapfilt2, hashrot(ren, ren + HASH_BIAS))) {
+    IRIns *ir = IR(ren);
+    ra_spill(as, ir);  /* Register renamed, so force a spill slot. */
+    RA_DBGX((as, "snaprensp $f $s", ren, ir->s));
+    return 1;  /* Found. */
+  }
+  return 0;  /* Not found. */
+}
+
+/* Prepare snapshot for next guard or throwing instruction. */
+static void asm_snap_prep(ASMState *as)
+{
+  if (as->snapalloc) {
+    /* Alloc on first invocation for each snapshot. */
+    as->snapalloc = 0;
+    asm_snap_alloc(as, as->snapno);
+    as->snaprename = as->T->nins;
+  } else {
+    /* Check any renames above the highwater mark. */
+    for (; as->snaprename < as->T->nins; as->snaprename++) {
+      IRIns *ir = &as->T->ir[as->snaprename];
+      if (asm_snap_checkrename(as, ir->op1))
+	ir->op2 = REF_BIAS-1;  /* Kill rename. */
+    }
+  }
+}
+
+/* Move to previous snapshot when we cross the current snapshot ref. */
+static void asm_snap_prev(ASMState *as)
+{
+  if (as->curins < as->snapref) {
+    uintptr_t ofs = (uintptr_t)(as->mctoporig - as->mcp);
+    if (ofs >= 0x10000) lj_trace_err(as->J, LJ_TRERR_MCODEOV);
+    do {
+      if (as->snapno == 0) return;
+      as->snapno--;
+      as->snapref = as->T->snap[as->snapno].ref;
+      as->T->snap[as->snapno].mcofs = (uint16_t)ofs;  /* Remember mcode ofs. */
+    } while (as->curins < as->snapref);  /* May have no ins inbetween. */
+    as->snapalloc = 1;
+  }
+}
+
+/* Fixup snapshot mcode offsetst. */
+static void asm_snap_fixup_mcofs(ASMState *as)
+{
+  uint32_t sz = (uint32_t)(as->mctoporig - as->mcp);
+  SnapShot *snap = as->T->snap;
+  SnapNo i;
+  for (i = as->T->nsnap-1; i > 0; i--) {
+    /* Compute offset from mcode start and store in correct snapshot. */
+    snap[i].mcofs = (uint16_t)(sz - snap[i-1].mcofs);
+  }
+  snap[0].mcofs = 0;
+}
+
+/* -- Miscellaneous helpers ----------------------------------------------- */
+
+/* Calculate stack adjustment. */
+static int32_t asm_stack_adjust(ASMState *as)
+{
+  if (as->evenspill <= SPS_FIXED)
+    return 0;
+  return sps_scale(sps_align(as->evenspill));
+}
+
+/* Must match with hash*() in lj_tab.c. */
+static uint32_t ir_khash(ASMState *as, IRIns *ir)
+{
+  uint32_t lo, hi;
+  UNUSED(as);
+  if (irt_isstr(ir->t)) {
+    return ir_kstr(ir)->sid;
+  } else if (irt_isnum(ir->t)) {
+    lo = ir_knum(ir)->u32.lo;
+    hi = ir_knum(ir)->u32.hi << 1;
+  } else if (irt_ispri(ir->t)) {
+    lj_assertA(!irt_isnil(ir->t), "hash of nil key");
+    return irt_type(ir->t)-IRT_FALSE;
+  } else {
+    lj_assertA(irt_isgcv(ir->t), "hash of bad IR type %d", irt_type(ir->t));
+    lo = u32ptr(ir_kgc(ir));
+#if LJ_GC64
+    hi = (uint32_t)(u64ptr(ir_kgc(ir)) >> 32) | (irt_toitype(ir->t) << 15);
+#else
+    hi = lo + HASH_BIAS;
+#endif
+  }
+  return hashrot(lo, hi);
+}
+
+/* -- Allocations --------------------------------------------------------- */
+
+static void asm_gencall(ASMState *as, const CCallInfo *ci, IRRef *args);
+static void asm_setupresult(ASMState *as, IRIns *ir, const CCallInfo *ci);
+
+static void asm_snew(ASMState *as, IRIns *ir)
+{
+  const CCallInfo *ci = &lj_ir_callinfo[IRCALL_lj_str_new];
+  IRRef args[3];
+  asm_snap_prep(as);
+  args[0] = ASMREF_L;  /* lua_State *L    */
+  args[1] = ir->op1;   /* const char *str */
+  args[2] = ir->op2;   /* size_t len      */
+  as->gcsteps++;
+  asm_setupresult(as, ir, ci);  /* GCstr * */
+  asm_gencall(as, ci, args);
+}
+
+static void asm_tnew(ASMState *as, IRIns *ir)
+{
+  const CCallInfo *ci = &lj_ir_callinfo[IRCALL_lj_tab_new1];
+  IRRef args[2];
+  asm_snap_prep(as);
+  args[0] = ASMREF_L;     /* lua_State *L    */
+  args[1] = ASMREF_TMP1;  /* uint32_t ahsize */
+  as->gcsteps++;
+  asm_setupresult(as, ir, ci);  /* GCtab * */
+  asm_gencall(as, ci, args);
+  ra_allockreg(as, ir->op1 | (ir->op2 << 24), ra_releasetmp(as, ASMREF_TMP1));
+}
+
+static void asm_tdup(ASMState *as, IRIns *ir)
+{
+  const CCallInfo *ci = &lj_ir_callinfo[IRCALL_lj_tab_dup];
+  IRRef args[2];
+  asm_snap_prep(as);
+  args[0] = ASMREF_L;  /* lua_State *L    */
+  args[1] = ir->op1;   /* const GCtab *kt */
+  as->gcsteps++;
+  asm_setupresult(as, ir, ci);  /* GCtab * */
+  asm_gencall(as, ci, args);
+}
+
+static void asm_gc_check(ASMState *as);
+
+/* Explicit GC step. */
+static void asm_gcstep(ASMState *as, IRIns *ir)
+{
+  IRIns *ira;
+  for (ira = IR(as->stopins+1); ira < ir; ira++)
+    if ((ira->o == IR_TNEW || ira->o == IR_TDUP ||
+	 (LJ_HASFFI && (ira->o == IR_CNEW || ira->o == IR_CNEWI))) &&
+	ra_used(ira))
+      as->gcsteps++;
+  if (as->gcsteps)
+    asm_gc_check(as);
+  as->gcsteps = 0x80000000;  /* Prevent implicit GC check further up. */
+}
+
+/* -- Buffer operations --------------------------------------------------- */
+
+static void asm_tvptr(ASMState *as, Reg dest, IRRef ref, MSize mode);
+#if LJ_HASBUFFER
+static void asm_bufhdr_write(ASMState *as, Reg sb);
+#endif
+
+static void asm_bufhdr(ASMState *as, IRIns *ir)
+{
+  Reg sb = ra_dest(as, ir, RSET_GPR);
+  switch (ir->op2) {
+  case IRBUFHDR_RESET: {
+    Reg tmp = ra_scratch(as, rset_exclude(RSET_GPR, sb));
+    IRIns irbp;
+    irbp.ot = IRT(0, IRT_PTR);  /* Buffer data pointer type. */
+    emit_storeofs(as, &irbp, tmp, sb, offsetof(SBuf, w));
+    emit_loadofs(as, &irbp, tmp, sb, offsetof(SBuf, b));
+    break;
+    }
+  case IRBUFHDR_APPEND: {
+    /* Rematerialize const buffer pointer instead of likely spill. */
+    IRIns *irp = IR(ir->op1);
+    if (!(ra_hasreg(irp->r) || irp == ir-1 ||
+	  (irp == ir-2 && !ra_used(ir-1)))) {
+      while (!(irp->o == IR_BUFHDR && irp->op2 == IRBUFHDR_RESET))
+	irp = IR(irp->op1);
+      if (irref_isk(irp->op1)) {
+	ra_weak(as, ra_allocref(as, ir->op1, RSET_GPR));
+	ir = irp;
+      }
+    }
+    break;
+    }
+#if LJ_HASBUFFER
+  case IRBUFHDR_WRITE:
+    asm_bufhdr_write(as, sb);
+    break;
+#endif
+  default: lj_assertA(0, "bad BUFHDR op2 %d", ir->op2); break;
+  }
+#if LJ_TARGET_X86ORX64
+  ra_left(as, sb, ir->op1);
+#else
+  ra_leftov(as, sb, ir->op1);
+#endif
+}
+
+static void asm_bufput(ASMState *as, IRIns *ir)
+{
+  const CCallInfo *ci = &lj_ir_callinfo[IRCALL_lj_buf_putstr];
+  IRRef args[3];
+  IRIns *irs;
+  int kchar = -129;
+  args[0] = ir->op1;  /* SBuf * */
+  args[1] = ir->op2;  /* GCstr * */
+  irs = IR(ir->op2);
+  lj_assertA(irt_isstr(irs->t),
+	     "BUFPUT of non-string IR %04d", ir->op2 - REF_BIAS);
+  if (irs->o == IR_KGC) {
+    GCstr *s = ir_kstr(irs);
+    if (s->len == 1) {  /* Optimize put of single-char string constant. */
+      kchar = (int8_t)strdata(s)[0];  /* Signed! */
+      args[1] = ASMREF_TMP1;  /* int, truncated to char */
+      ci = &lj_ir_callinfo[IRCALL_lj_buf_putchar];
+    }
+  } else if (mayfuse(as, ir->op2) && ra_noreg(irs->r)) {
+    if (irs->o == IR_TOSTR) {  /* Fuse number to string conversions. */
+      if (irs->op2 == IRTOSTR_NUM) {
+	args[1] = ASMREF_TMP1;  /* TValue * */
+	ci = &lj_ir_callinfo[IRCALL_lj_strfmt_putnum];
+      } else {
+	lj_assertA(irt_isinteger(IR(irs->op1)->t),
+		   "TOSTR of non-numeric IR %04d", irs->op1);
+	args[1] = irs->op1;  /* int */
+	if (irs->op2 == IRTOSTR_INT)
+	  ci = &lj_ir_callinfo[IRCALL_lj_strfmt_putint];
+	else
+	  ci = &lj_ir_callinfo[IRCALL_lj_buf_putchar];
+      }
+    } else if (irs->o == IR_SNEW) {  /* Fuse string allocation. */
+      args[1] = irs->op1;  /* const void * */
+      args[2] = irs->op2;  /* MSize */
+      ci = &lj_ir_callinfo[IRCALL_lj_buf_putmem];
+    }
+  }
+  asm_setupresult(as, ir, ci);  /* SBuf * */
+  asm_gencall(as, ci, args);
+  if (args[1] == ASMREF_TMP1) {
+    Reg tmp = ra_releasetmp(as, ASMREF_TMP1);
+    if (kchar == -129)
+      asm_tvptr(as, tmp, irs->op1, IRTMPREF_IN1);
+    else
+      ra_allockreg(as, kchar, tmp);
+  }
+}
+
+static void asm_bufstr(ASMState *as, IRIns *ir)
+{
+  const CCallInfo *ci = &lj_ir_callinfo[IRCALL_lj_buf_tostr];
+  IRRef args[1];
+  args[0] = ir->op1;  /* SBuf *sb */
+  as->gcsteps++;
+  asm_setupresult(as, ir, ci);  /* GCstr * */
+  asm_gencall(as, ci, args);
+}
+
+/* -- Type conversions ---------------------------------------------------- */
+
+static void asm_tostr(ASMState *as, IRIns *ir)
+{
+  const CCallInfo *ci;
+  IRRef args[2];
+  asm_snap_prep(as);
+  args[0] = ASMREF_L;
+  as->gcsteps++;
+  if (ir->op2 == IRTOSTR_NUM) {
+    args[1] = ASMREF_TMP1;  /* cTValue * */
+    ci = &lj_ir_callinfo[IRCALL_lj_strfmt_num];
+  } else {
+    args[1] = ir->op1;  /* int32_t k */
+    if (ir->op2 == IRTOSTR_INT)
+      ci = &lj_ir_callinfo[IRCALL_lj_strfmt_int];
+    else
+      ci = &lj_ir_callinfo[IRCALL_lj_strfmt_char];
+  }
+  asm_setupresult(as, ir, ci);  /* GCstr * */
+  asm_gencall(as, ci, args);
+  if (ir->op2 == IRTOSTR_NUM)
+    asm_tvptr(as, ra_releasetmp(as, ASMREF_TMP1), ir->op1, IRTMPREF_IN1);
+}
+
+#if LJ_32 && LJ_HASFFI && !LJ_SOFTFP && !LJ_TARGET_X86
+static void asm_conv64(ASMState *as, IRIns *ir)
+{
+  IRType st = (IRType)((ir-1)->op2 & IRCONV_SRCMASK);
+  IRType dt = (((ir-1)->op2 & IRCONV_DSTMASK) >> IRCONV_DSH);
+  IRCallID id;
+  IRRef args[2];
+  lj_assertA((ir-1)->o == IR_CONV && ir->o == IR_HIOP,
+	     "not a CONV/HIOP pair at IR %04d", (int)(ir - as->ir) - REF_BIAS);
+  args[LJ_BE] = (ir-1)->op1;
+  args[LJ_LE] = ir->op1;
+  if (st == IRT_NUM || st == IRT_FLOAT) {
+    id = IRCALL_fp64_d2l + ((st == IRT_FLOAT) ? 2 : 0) + (dt - IRT_I64);
+    ir--;
+  } else {
+    id = IRCALL_fp64_l2d + ((dt == IRT_FLOAT) ? 2 : 0) + (st - IRT_I64);
+  }
+  {
+#if LJ_TARGET_ARM && !LJ_ABI_SOFTFP
+    CCallInfo cim = lj_ir_callinfo[id], *ci = &cim;
+    cim.flags |= CCI_VARARG;  /* These calls don't use the hard-float ABI! */
+#else
+    const CCallInfo *ci = &lj_ir_callinfo[id];
+#endif
+    asm_setupresult(as, ir, ci);
+    asm_gencall(as, ci, args);
+  }
+}
+#endif
+
+/* -- Memory references --------------------------------------------------- */
+
+static void asm_newref(ASMState *as, IRIns *ir)
+{
+  const CCallInfo *ci = &lj_ir_callinfo[IRCALL_lj_tab_newkey];
+  IRRef args[3];
+  if (ir->r == RID_SINK)
+    return;
+  asm_snap_prep(as);
+  args[0] = ASMREF_L;     /* lua_State *L */
+  args[1] = ir->op1;      /* GCtab *t     */
+  args[2] = ASMREF_TMP1;  /* cTValue *key */
+  asm_setupresult(as, ir, ci);  /* TValue * */
+  asm_gencall(as, ci, args);
+  asm_tvptr(as, ra_releasetmp(as, ASMREF_TMP1), ir->op2, IRTMPREF_IN1);
+}
+
+static void asm_tmpref(ASMState *as, IRIns *ir)
+{
+  Reg r = ra_dest(as, ir, RSET_GPR);
+  asm_tvptr(as, r, ir->op1, ir->op2);
+}
+
+static void asm_lref(ASMState *as, IRIns *ir)
+{
+  Reg r = ra_dest(as, ir, RSET_GPR);
+#if LJ_TARGET_X86ORX64
+  ra_left(as, r, ASMREF_L);
+#else
+  ra_leftov(as, r, ASMREF_L);
+#endif
+}
+
+/* -- Calls --------------------------------------------------------------- */
+
+/* Collect arguments from CALL* and CARG instructions. */
+static void asm_collectargs(ASMState *as, IRIns *ir,
+			    const CCallInfo *ci, IRRef *args)
+{
+  uint32_t n = CCI_XNARGS(ci);
+  /* Account for split args. */
+  lj_assertA(n <= CCI_NARGS_MAX*2, "too many args %d to collect", n);
+  if ((ci->flags & CCI_L)) { *args++ = ASMREF_L; n--; }
+  while (n-- > 1) {
+    ir = IR(ir->op1);
+    lj_assertA(ir->o == IR_CARG, "malformed CALL arg tree");
+    args[n] = ir->op2 == REF_NIL ? 0 : ir->op2;
+  }
+  args[0] = ir->op1 == REF_NIL ? 0 : ir->op1;
+  lj_assertA(IR(ir->op1)->o != IR_CARG, "malformed CALL arg tree");
+}
+
+/* Reconstruct CCallInfo flags for CALLX*. */
+static uint32_t asm_callx_flags(ASMState *as, IRIns *ir)
+{
+  uint32_t nargs = 0;
+  if (ir->op1 != REF_NIL) {  /* Count number of arguments first. */
+    IRIns *ira = IR(ir->op1);
+    nargs++;
+    while (ira->o == IR_CARG) { nargs++; ira = IR(ira->op1); }
+  }
+#if LJ_HASFFI
+  if (IR(ir->op2)->o == IR_CARG) {  /* Copy calling convention info. */
+    CTypeID id = (CTypeID)IR(IR(ir->op2)->op2)->i;
+    CType *ct = ctype_get(ctype_ctsG(J2G(as->J)), id);
+    nargs |= ((ct->info & CTF_VARARG) ? CCI_VARARG : 0);
+#if LJ_TARGET_X86
+    nargs |= (ctype_cconv(ct->info) << CCI_CC_SHIFT);
+#endif
+  }
+#endif
+  return (nargs | (ir->t.irt << CCI_OTSHIFT));
+}
+
+static void asm_callid(ASMState *as, IRIns *ir, IRCallID id)
+{
+  const CCallInfo *ci = &lj_ir_callinfo[id];
+  IRRef args[2];
+  args[0] = ir->op1;
+  args[1] = ir->op2;
+  asm_setupresult(as, ir, ci);
+  asm_gencall(as, ci, args);
+}
+
+static void asm_call(ASMState *as, IRIns *ir)
+{
+  IRRef args[CCI_NARGS_MAX];
+  const CCallInfo *ci = &lj_ir_callinfo[ir->op2];
+  asm_collectargs(as, ir, ci, args);
+  asm_setupresult(as, ir, ci);
+  asm_gencall(as, ci, args);
+}
+
+/* -- PHI and loop handling ----------------------------------------------- */
+
+/* Break a PHI cycle by renaming to a free register (evict if needed). */
+static void asm_phi_break(ASMState *as, RegSet blocked, RegSet blockedby,
+			  RegSet allow)
+{
+  RegSet candidates = blocked & allow;
+  if (candidates) {  /* If this register file has candidates. */
+    /* Note: the set for ra_pick cannot be empty, since each register file
+    ** has some registers never allocated to PHIs.
+    */
+    Reg down, up = ra_pick(as, ~blocked & allow);  /* Get a free register. */
+    if (candidates & ~blockedby)  /* Optimize shifts, else it's a cycle. */
+      candidates = candidates & ~blockedby;
+    down = rset_picktop(candidates);  /* Pick candidate PHI register. */
+    ra_rename(as, down, up);  /* And rename it to the free register. */
+  }
+}
+
+/* PHI register shuffling.
+**
+** The allocator tries hard to preserve PHI register assignments across
+** the loop body. Most of the time this loop does nothing, since there
+** are no register mismatches.
+**
+** If a register mismatch is detected and ...
+** - the register is currently free: rename it.
+** - the register is blocked by an invariant: restore/remat and rename it.
+** - Otherwise the register is used by another PHI, so mark it as blocked.
+**
+** The renames are order-sensitive, so just retry the loop if a register
+** is marked as blocked, but has been freed in the meantime. A cycle is
+** detected if all of the blocked registers are allocated. To break the
+** cycle rename one of them to a free register and retry.
+**
+** Note that PHI spill slots are kept in sync and don't need to be shuffled.
+*/
+static void asm_phi_shuffle(ASMState *as)
+{
+  RegSet work;
+
+  /* Find and resolve PHI register mismatches. */
+  for (;;) {
+    RegSet blocked = RSET_EMPTY;
+    RegSet blockedby = RSET_EMPTY;
+    RegSet phiset = as->phiset;
+    while (phiset) {  /* Check all left PHI operand registers. */
+      Reg r = rset_pickbot(phiset);
+      IRIns *irl = IR(as->phireg[r]);
+      Reg left = irl->r;
+      if (r != left) {  /* Mismatch? */
+	if (!rset_test(as->freeset, r)) {  /* PHI register blocked? */
+	  IRRef ref = regcost_ref(as->cost[r]);
+	  /* Blocked by other PHI (w/reg)? */
+	  if (!ra_iskref(ref) && irt_ismarked(IR(ref)->t)) {
+	    rset_set(blocked, r);
+	    if (ra_hasreg(left))
+	      rset_set(blockedby, left);
+	    left = RID_NONE;
+	  } else {  /* Otherwise grab register from invariant. */
+	    ra_restore(as, ref);
+	    checkmclim(as);
+	  }
+	}
+	if (ra_hasreg(left)) {
+	  ra_rename(as, left, r);
+	  checkmclim(as);
+	}
+      }
+      rset_clear(phiset, r);
+    }
+    if (!blocked) break;  /* Finished. */
+    if (!(as->freeset & blocked)) {  /* Break cycles if none are free. */
+      asm_phi_break(as, blocked, blockedby, RSET_GPR);
+      if (!LJ_SOFTFP) asm_phi_break(as, blocked, blockedby, RSET_FPR);
+      checkmclim(as);
+    }  /* Else retry some more renames. */
+  }
+
+  /* Restore/remat invariants whose registers are modified inside the loop. */
+#if !LJ_SOFTFP
+  work = as->modset & ~(as->freeset | as->phiset) & RSET_FPR;
+  while (work) {
+    Reg r = rset_pickbot(work);
+    ra_restore(as, regcost_ref(as->cost[r]));
+    rset_clear(work, r);
+    checkmclim(as);
+  }
+#endif
+  work = as->modset & ~(as->freeset | as->phiset);
+  while (work) {
+    Reg r = rset_pickbot(work);
+    ra_restore(as, regcost_ref(as->cost[r]));
+    rset_clear(work, r);
+    checkmclim(as);
+  }
+
+  /* Allocate and save all unsaved PHI regs and clear marks. */
+  work = as->phiset;
+  while (work) {
+    Reg r = rset_picktop(work);
+    IRRef lref = as->phireg[r];
+    IRIns *ir = IR(lref);
+    if (ra_hasspill(ir->s)) {  /* Left PHI gained a spill slot? */
+      irt_clearmark(ir->t);  /* Handled here, so clear marker now. */
+      ra_alloc1(as, lref, RID2RSET(r));
+      ra_save(as, ir, r);  /* Save to spill slot inside the loop. */
+      checkmclim(as);
+    }
+    rset_clear(work, r);
+  }
+}
+
+/* Copy unsynced left/right PHI spill slots. Rarely needed. */
+static void asm_phi_copyspill(ASMState *as)
+{
+  int need = 0;
+  IRIns *ir;
+  for (ir = IR(as->orignins-1); ir->o == IR_PHI; ir--)
+    if (ra_hasspill(ir->s) && ra_hasspill(IR(ir->op1)->s))
+      need |= irt_isfp(ir->t) ? 2 : 1;  /* Unsynced spill slot? */
+  if ((need & 1)) {  /* Copy integer spill slots. */
+#if !LJ_TARGET_X86ORX64
+    Reg r = RID_TMP;
+#else
+    Reg r = RID_RET;
+    if ((as->freeset & RSET_GPR))
+      r = rset_pickbot((as->freeset & RSET_GPR));
+    else
+      emit_spload(as, IR(regcost_ref(as->cost[r])), r, SPOFS_TMP);
+#endif
+    for (ir = IR(as->orignins-1); ir->o == IR_PHI; ir--) {
+      if (ra_hasspill(ir->s)) {
+	IRIns *irl = IR(ir->op1);
+	if (ra_hasspill(irl->s) && !irt_isfp(ir->t)) {
+	  emit_spstore(as, irl, r, sps_scale(irl->s));
+	  emit_spload(as, ir, r, sps_scale(ir->s));
+	  checkmclim(as);
+	}
+      }
+    }
+#if LJ_TARGET_X86ORX64
+    if (!rset_test(as->freeset, r))
+      emit_spstore(as, IR(regcost_ref(as->cost[r])), r, SPOFS_TMP);
+#endif
+  }
+#if !LJ_SOFTFP
+  if ((need & 2)) {  /* Copy FP spill slots. */
+#if LJ_TARGET_X86
+    Reg r = RID_XMM0;
+#else
+    Reg r = RID_FPRET;
+#endif
+    if ((as->freeset & RSET_FPR))
+      r = rset_pickbot((as->freeset & RSET_FPR));
+    if (!rset_test(as->freeset, r))
+      emit_spload(as, IR(regcost_ref(as->cost[r])), r, SPOFS_TMP);
+    for (ir = IR(as->orignins-1); ir->o == IR_PHI; ir--) {
+      if (ra_hasspill(ir->s)) {
+	IRIns *irl = IR(ir->op1);
+	if (ra_hasspill(irl->s) && irt_isfp(ir->t)) {
+	  emit_spstore(as, irl, r, sps_scale(irl->s));
+	  emit_spload(as, ir, r, sps_scale(ir->s));
+	  checkmclim(as);
+	}
+      }
+    }
+    if (!rset_test(as->freeset, r))
+      emit_spstore(as, IR(regcost_ref(as->cost[r])), r, SPOFS_TMP);
+  }
+#endif
+}
+
+/* Emit renames for left PHIs which are only spilled outside the loop. */
+static void asm_phi_fixup(ASMState *as)
+{
+  RegSet work = as->phiset;
+  while (work) {
+    Reg r = rset_picktop(work);
+    IRRef lref = as->phireg[r];
+    IRIns *ir = IR(lref);
+    if (irt_ismarked(ir->t)) {
+      irt_clearmark(ir->t);
+      /* Left PHI gained a spill slot before the loop? */
+      if (ra_hasspill(ir->s)) {
+	ra_addrename(as, r, lref, as->loopsnapno);
+      }
+    }
+    rset_clear(work, r);
+  }
+}
+
+/* Setup right PHI reference. */
+static void asm_phi(ASMState *as, IRIns *ir)
+{
+  RegSet allow = ((!LJ_SOFTFP && irt_isfp(ir->t)) ? RSET_FPR : RSET_GPR) &
+		 ~as->phiset;
+  RegSet afree = (as->freeset & allow);
+  IRIns *irl = IR(ir->op1);
+  IRIns *irr = IR(ir->op2);
+  if (ir->r == RID_SINK)  /* Sink PHI. */
+    return;
+  /* Spill slot shuffling is not implemented yet (but rarely needed). */
+  if (ra_hasspill(irl->s) || ra_hasspill(irr->s))
+    lj_trace_err(as->J, LJ_TRERR_NYIPHI);
+  /* Leave at least one register free for non-PHIs (and PHI cycle breaking). */
+  if ((afree & (afree-1))) {  /* Two or more free registers? */
+    Reg r;
+    if (ra_noreg(irr->r)) {  /* Get a register for the right PHI. */
+      r = ra_allocref(as, ir->op2, allow);
+    } else {  /* Duplicate right PHI, need a copy (rare). */
+      r = ra_scratch(as, allow);
+      emit_movrr(as, irr, r, irr->r);
+    }
+    ir->r = (uint8_t)r;
+    rset_set(as->phiset, r);
+    as->phireg[r] = (IRRef1)ir->op1;
+    irt_setmark(irl->t);  /* Marks left PHIs _with_ register. */
+    if (ra_noreg(irl->r))
+      ra_sethint(irl->r, r); /* Set register hint for left PHI. */
+  } else {  /* Otherwise allocate a spill slot. */
+    /* This is overly restrictive, but it triggers only on synthetic code. */
+    if (ra_hasreg(irl->r) || ra_hasreg(irr->r))
+      lj_trace_err(as->J, LJ_TRERR_NYIPHI);
+    ra_spill(as, ir);
+    irr->s = ir->s;  /* Set right PHI spill slot. Sync left slot later. */
+  }
+}
+
+static void asm_loop_fixup(ASMState *as);
+
+/* Middle part of a loop. */
+static void asm_loop(ASMState *as)
+{
+  MCode *mcspill;
+  /* LOOP is a guard, so the snapno is up to date. */
+  as->loopsnapno = as->snapno;
+  if (as->gcsteps)
+    asm_gc_check(as);
+  /* LOOP marks the transition from the variant to the invariant part. */
+  as->flagmcp = as->invmcp = NULL;
+  as->sectref = 0;
+  if (!neverfuse(as)) as->fuseref = 0;
+  asm_phi_shuffle(as);
+  mcspill = as->mcp;
+  asm_phi_copyspill(as);
+  asm_loop_fixup(as);
+  as->mcloop = as->mcp;
+  RA_DBGX((as, "===== LOOP ====="));
+  if (!as->realign) RA_DBG_FLUSH();
+  if (as->mcp != mcspill)
+    emit_jmp(as, mcspill);
+}
+
+/* -- Target-specific assembler ------------------------------------------- */
+
+#if LJ_TARGET_X86ORX64
+#include "lj_asm_x86.h"
+#elif LJ_TARGET_ARM
+#include "lj_asm_arm.h"
+#elif LJ_TARGET_ARM64
+#include "lj_asm_arm64.h"
+#elif LJ_TARGET_PPC
+#include "lj_asm_ppc.h"
+#elif LJ_TARGET_MIPS
+#include "lj_asm_mips.h"
+#else
+#error "Missing assembler for target CPU"
+#endif
+
+/* -- Common instruction helpers ------------------------------------------ */
+
+#if !LJ_SOFTFP32
+#if !LJ_TARGET_X86ORX64
+#define asm_ldexp(as, ir)	asm_callid(as, ir, IRCALL_ldexp)
+#endif
+
+static void asm_pow(ASMState *as, IRIns *ir)
+{
+#if LJ_64 && LJ_HASFFI
+  if (!irt_isnum(ir->t))
+    asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_powi64 :
+					  IRCALL_lj_carith_powu64);
+  else
+#endif
+  asm_callid(as, ir, IRCALL_pow);
+}
+
+static void asm_div(ASMState *as, IRIns *ir)
+{
+#if LJ_64 && LJ_HASFFI
+  if (!irt_isnum(ir->t))
+    asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_divi64 :
+					  IRCALL_lj_carith_divu64);
+  else
+#endif
+    asm_fpdiv(as, ir);
+}
+#endif
+
+static void asm_mod(ASMState *as, IRIns *ir)
+{
+#if LJ_64 && LJ_HASFFI
+  if (!irt_isint(ir->t))
+    asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_modi64 :
+					  IRCALL_lj_carith_modu64);
+  else
+#endif
+    asm_callid(as, ir, IRCALL_lj_vm_modi);
+}
+
+static void asm_fuseequal(ASMState *as, IRIns *ir)
+{
+  /* Fuse HREF + EQ/NE. */
+  if ((ir-1)->o == IR_HREF && ir->op1 == as->curins-1) {
+    as->curins--;
+    asm_href(as, ir-1, (IROp)ir->o);
+  } else {
+    asm_equal(as, ir);
+  }
+}
+
+static void asm_alen(ASMState *as, IRIns *ir)
+{
+  asm_callid(as, ir, ir->op2 == REF_NIL ? IRCALL_lj_tab_len :
+					  IRCALL_lj_tab_len_hint);
+}
+
+/* -- Instruction dispatch ------------------------------------------------ */
+
+/* Assemble a single instruction. */
+static void asm_ir(ASMState *as, IRIns *ir)
+{
+  switch ((IROp)ir->o) {
+  /* Miscellaneous ops. */
+  case IR_LOOP: asm_loop(as); break;
+  case IR_NOP: case IR_XBAR:
+    lj_assertA(!ra_used(ir),
+	       "IR %04d not unused", (int)(ir - as->ir) - REF_BIAS);
+    break;
+  case IR_USE:
+    ra_alloc1(as, ir->op1, irt_isfp(ir->t) ? RSET_FPR : RSET_GPR); break;
+  case IR_PHI: asm_phi(as, ir); break;
+  case IR_HIOP: asm_hiop(as, ir); break;
+  case IR_GCSTEP: asm_gcstep(as, ir); break;
+  case IR_PROF: asm_prof(as, ir); break;
+
+  /* Guarded assertions. */
+  case IR_LT: case IR_GE: case IR_LE: case IR_GT:
+  case IR_ULT: case IR_UGE: case IR_ULE: case IR_UGT:
+  case IR_ABC:
+    asm_comp(as, ir);
+    break;
+  case IR_EQ: case IR_NE: asm_fuseequal(as, ir); break;
+
+  case IR_RETF: asm_retf(as, ir); break;
+
+  /* Bit ops. */
+  case IR_BNOT: asm_bnot(as, ir); break;
+  case IR_BSWAP: asm_bswap(as, ir); break;
+  case IR_BAND: asm_band(as, ir); break;
+  case IR_BOR: asm_bor(as, ir); break;
+  case IR_BXOR: asm_bxor(as, ir); break;
+  case IR_BSHL: asm_bshl(as, ir); break;
+  case IR_BSHR: asm_bshr(as, ir); break;
+  case IR_BSAR: asm_bsar(as, ir); break;
+  case IR_BROL: asm_brol(as, ir); break;
+  case IR_BROR: asm_bror(as, ir); break;
+
+  /* Arithmetic ops. */
+  case IR_ADD: asm_add(as, ir); break;
+  case IR_SUB: asm_sub(as, ir); break;
+  case IR_MUL: asm_mul(as, ir); break;
+  case IR_MOD: asm_mod(as, ir); break;
+  case IR_NEG: asm_neg(as, ir); break;
+#if LJ_SOFTFP32
+  case IR_DIV: case IR_POW: case IR_ABS:
+  case IR_LDEXP: case IR_FPMATH: case IR_TOBIT:
+    /* Unused for LJ_SOFTFP32. */
+    lj_assertA(0, "IR %04d with unused op %d",
+		  (int)(ir - as->ir) - REF_BIAS, ir->o);
+    break;
+#else
+  case IR_DIV: asm_div(as, ir); break;
+  case IR_POW: asm_pow(as, ir); break;
+  case IR_ABS: asm_abs(as, ir); break;
+  case IR_LDEXP: asm_ldexp(as, ir); break;
+  case IR_FPMATH: asm_fpmath(as, ir); break;
+  case IR_TOBIT: asm_tobit(as, ir); break;
+#endif
+  case IR_MIN: asm_min(as, ir); break;
+  case IR_MAX: asm_max(as, ir); break;
+
+  /* Overflow-checking arithmetic ops. */
+  case IR_ADDOV: asm_addov(as, ir); break;
+  case IR_SUBOV: asm_subov(as, ir); break;
+  case IR_MULOV: asm_mulov(as, ir); break;
+
+  /* Memory references. */
+  case IR_AREF: asm_aref(as, ir); break;
+  case IR_HREF: asm_href(as, ir, 0); break;
+  case IR_HREFK: asm_hrefk(as, ir); break;
+  case IR_NEWREF: asm_newref(as, ir); break;
+  case IR_UREFO: case IR_UREFC: asm_uref(as, ir); break;
+  case IR_FREF: asm_fref(as, ir); break;
+  case IR_TMPREF: asm_tmpref(as, ir); break;
+  case IR_STRREF: asm_strref(as, ir); break;
+  case IR_LREF: asm_lref(as, ir); break;
+
+  /* Loads and stores. */
+  case IR_ALOAD: case IR_HLOAD: case IR_ULOAD: case IR_VLOAD:
+    asm_ahuvload(as, ir);
+    break;
+  case IR_FLOAD: asm_fload(as, ir); break;
+  case IR_XLOAD: asm_xload(as, ir); break;
+  case IR_SLOAD: asm_sload(as, ir); break;
+  case IR_ALEN: asm_alen(as, ir); break;
+
+  case IR_ASTORE: case IR_HSTORE: case IR_USTORE: asm_ahustore(as, ir); break;
+  case IR_FSTORE: asm_fstore(as, ir); break;
+  case IR_XSTORE: asm_xstore(as, ir); break;
+
+  /* Allocations. */
+  case IR_SNEW: case IR_XSNEW: asm_snew(as, ir); break;
+  case IR_TNEW: asm_tnew(as, ir); break;
+  case IR_TDUP: asm_tdup(as, ir); break;
+  case IR_CNEW: case IR_CNEWI:
+#if LJ_HASFFI
+    asm_cnew(as, ir);
+#else
+    lj_assertA(0, "IR %04d with unused op %d",
+		  (int)(ir - as->ir) - REF_BIAS, ir->o);
+#endif
+    break;
+
+  /* Buffer operations. */
+  case IR_BUFHDR: asm_bufhdr(as, ir); break;
+  case IR_BUFPUT: asm_bufput(as, ir); break;
+  case IR_BUFSTR: asm_bufstr(as, ir); break;
+
+  /* Write barriers. */
+  case IR_TBAR: asm_tbar(as, ir); break;
+  case IR_OBAR: asm_obar(as, ir); break;
+
+  /* Type conversions. */
+  case IR_CONV: asm_conv(as, ir); break;
+  case IR_TOSTR: asm_tostr(as, ir); break;
+  case IR_STRTO: asm_strto(as, ir); break;
+
+  /* Calls. */
+  case IR_CALLA:
+    as->gcsteps++;
+    /* fallthrough */
+  case IR_CALLN: case IR_CALLL: case IR_CALLS: asm_call(as, ir); break;
+  case IR_CALLXS: asm_callx(as, ir); break;
+  case IR_CARG: break;
+
+  default:
+    setintV(&as->J->errinfo, ir->o);
+    lj_trace_err_info(as->J, LJ_TRERR_NYIIR);
+    break;
+  }
+}
+
+/* -- Head of trace ------------------------------------------------------- */
+
+/* Head of a root trace. */
+static void asm_head_root(ASMState *as)
+{
+  int32_t spadj;
+  asm_head_root_base(as);
+  emit_setvmstate(as, (int32_t)as->T->traceno);
+  spadj = asm_stack_adjust(as);
+  as->T->spadjust = (uint16_t)spadj;
+  emit_spsub(as, spadj);
+  /* Root traces assume a checked stack for the starting proto. */
+  as->T->topslot = gcref(as->T->startpt)->pt.framesize;
+}
+
+/* Head of a side trace.
+**
+** The current simplistic algorithm requires that all slots inherited
+** from the parent are live in a register between pass 2 and pass 3. This
+** avoids the complexity of stack slot shuffling. But of course this may
+** overflow the register set in some cases and cause the dreaded error:
+** "NYI: register coalescing too complex". A refined algorithm is needed.
+*/
+static void asm_head_side(ASMState *as)
+{
+  IRRef1 sloadins[RID_MAX];
+  RegSet allow = RSET_ALL;  /* Inverse of all coalesced registers. */
+  RegSet live = RSET_EMPTY;  /* Live parent registers. */
+  IRIns *irp = &as->parent->ir[REF_BASE];  /* Parent base. */
+  int32_t spadj, spdelta;
+  int pass2 = 0;
+  int pass3 = 0;
+  IRRef i;
+
+  if (as->snapno && as->topslot > as->parent->topslot) {
+    /* Force snap #0 alloc to prevent register overwrite in stack check. */
+    asm_snap_alloc(as, 0);
+  }
+  allow = asm_head_side_base(as, irp, allow);
+
+  /* Scan all parent SLOADs and collect register dependencies. */
+  for (i = as->stopins; i > REF_BASE; i--) {
+    IRIns *ir = IR(i);
+    RegSP rs;
+    lj_assertA((ir->o == IR_SLOAD && (ir->op2 & IRSLOAD_PARENT)) ||
+	       (LJ_SOFTFP && ir->o == IR_HIOP) || ir->o == IR_PVAL,
+	       "IR %04d has bad parent op %d",
+	       (int)(ir - as->ir) - REF_BIAS, ir->o);
+    rs = as->parentmap[i - REF_FIRST];
+    if (ra_hasreg(ir->r)) {
+      rset_clear(allow, ir->r);
+      if (ra_hasspill(ir->s)) {
+	ra_save(as, ir, ir->r);
+	checkmclim(as);
+      }
+    } else if (ra_hasspill(ir->s)) {
+      irt_setmark(ir->t);
+      pass2 = 1;
+    }
+    if (ir->r == rs) {  /* Coalesce matching registers right now. */
+      ra_free(as, ir->r);
+    } else if (ra_hasspill(regsp_spill(rs))) {
+      if (ra_hasreg(ir->r))
+	pass3 = 1;
+    } else if (ra_used(ir)) {
+      sloadins[rs] = (IRRef1)i;
+      rset_set(live, rs);  /* Block live parent register. */
+    }
+  }
+
+  /* Calculate stack frame adjustment. */
+  spadj = asm_stack_adjust(as);
+  spdelta = spadj - (int32_t)as->parent->spadjust;
+  if (spdelta < 0) {  /* Don't shrink the stack frame. */
+    spadj = (int32_t)as->parent->spadjust;
+    spdelta = 0;
+  }
+  as->T->spadjust = (uint16_t)spadj;
+
+  /* Reload spilled target registers. */
+  if (pass2) {
+    for (i = as->stopins; i > REF_BASE; i--) {
+      IRIns *ir = IR(i);
+      if (irt_ismarked(ir->t)) {
+	RegSet mask;
+	Reg r;
+	RegSP rs;
+	irt_clearmark(ir->t);
+	rs = as->parentmap[i - REF_FIRST];
+	if (!ra_hasspill(regsp_spill(rs)))
+	  ra_sethint(ir->r, rs);  /* Hint may be gone, set it again. */
+	else if (sps_scale(regsp_spill(rs))+spdelta == sps_scale(ir->s))
+	  continue;  /* Same spill slot, do nothing. */
+	mask = ((!LJ_SOFTFP && irt_isfp(ir->t)) ? RSET_FPR : RSET_GPR) & allow;
+	if (mask == RSET_EMPTY)
+	  lj_trace_err(as->J, LJ_TRERR_NYICOAL);
+	r = ra_allocref(as, i, mask);
+	ra_save(as, ir, r);
+	rset_clear(allow, r);
+	if (r == rs) {  /* Coalesce matching registers right now. */
+	  ra_free(as, r);
+	  rset_clear(live, r);
+	} else if (ra_hasspill(regsp_spill(rs))) {
+	  pass3 = 1;
+	}
+	checkmclim(as);
+      }
+    }
+  }
+
+  /* Store trace number and adjust stack frame relative to the parent. */
+  emit_setvmstate(as, (int32_t)as->T->traceno);
+  emit_spsub(as, spdelta);
+
+#if !LJ_TARGET_X86ORX64
+  /* Restore BASE register from parent spill slot. */
+  if (ra_hasspill(irp->s))
+    emit_spload(as, IR(REF_BASE), IR(REF_BASE)->r, sps_scale(irp->s));
+#endif
+
+  /* Restore target registers from parent spill slots. */
+  if (pass3) {
+    RegSet work = ~as->freeset & RSET_ALL;
+    while (work) {
+      Reg r = rset_pickbot(work);
+      IRRef ref = regcost_ref(as->cost[r]);
+      RegSP rs = as->parentmap[ref - REF_FIRST];
+      rset_clear(work, r);
+      if (ra_hasspill(regsp_spill(rs))) {
+	int32_t ofs = sps_scale(regsp_spill(rs));
+	ra_free(as, r);
+	emit_spload(as, IR(ref), r, ofs);
+	checkmclim(as);
+      }
+    }
+  }
+
+  /* Shuffle registers to match up target regs with parent regs. */
+  for (;;) {
+    RegSet work;
+
+    /* Repeatedly coalesce free live registers by moving to their target. */
+    while ((work = as->freeset & live) != RSET_EMPTY) {
+      Reg rp = rset_pickbot(work);
+      IRIns *ir = IR(sloadins[rp]);
+      rset_clear(live, rp);
+      rset_clear(allow, rp);
+      ra_free(as, ir->r);
+      emit_movrr(as, ir, ir->r, rp);
+      checkmclim(as);
+    }
+
+    /* We're done if no live registers remain. */
+    if (live == RSET_EMPTY)
+      break;
+
+    /* Break cycles by renaming one target to a temp. register. */
+    if (live & RSET_GPR) {
+      RegSet tmpset = as->freeset & ~live & allow & RSET_GPR;
+      if (tmpset == RSET_EMPTY)
+	lj_trace_err(as->J, LJ_TRERR_NYICOAL);
+      ra_rename(as, rset_pickbot(live & RSET_GPR), rset_pickbot(tmpset));
+    }
+    if (!LJ_SOFTFP && (live & RSET_FPR)) {
+      RegSet tmpset = as->freeset & ~live & allow & RSET_FPR;
+      if (tmpset == RSET_EMPTY)
+	lj_trace_err(as->J, LJ_TRERR_NYICOAL);
+      ra_rename(as, rset_pickbot(live & RSET_FPR), rset_pickbot(tmpset));
+    }
+    checkmclim(as);
+    /* Continue with coalescing to fix up the broken cycle(s). */
+  }
+
+  /* Inherit top stack slot already checked by parent trace. */
+  as->T->topslot = as->parent->topslot;
+  if (as->topslot > as->T->topslot) {  /* Need to check for higher slot? */
+#ifdef EXITSTATE_CHECKEXIT
+    /* Highest exit + 1 indicates stack check. */
+    ExitNo exitno = as->T->nsnap;
+#else
+    /* Reuse the parent exit in the context of the parent trace. */
+    ExitNo exitno = as->J->exitno;
+#endif
+    as->T->topslot = (uint8_t)as->topslot;  /* Remember for child traces. */
+    asm_stack_check(as, as->topslot, irp, allow & RSET_GPR, exitno);
+  }
+}
+
+/* -- Tail of trace ------------------------------------------------------- */
+
+/* Get base slot for a snapshot. */
+static BCReg asm_baseslot(ASMState *as, SnapShot *snap, int *gotframe)
+{
+  SnapEntry *map = &as->T->snapmap[snap->mapofs];
+  MSize n;
+  for (n = snap->nent; n > 0; n--) {
+    SnapEntry sn = map[n-1];
+    if ((sn & SNAP_FRAME)) {
+      *gotframe = 1;
+      return snap_slot(sn) - LJ_FR2;
+    }
+  }
+  return 0;
+}
+
+/* Link to another trace. */
+static void asm_tail_link(ASMState *as)
+{
+  SnapNo snapno = as->T->nsnap-1;  /* Last snapshot. */
+  SnapShot *snap = &as->T->snap[snapno];
+  int gotframe = 0;
+  BCReg baseslot = asm_baseslot(as, snap, &gotframe);
+
+  as->topslot = snap->topslot;
+  checkmclim(as);
+  ra_allocref(as, REF_BASE, RID2RSET(RID_BASE));
+
+  if (as->T->link == 0) {
+    /* Setup fixed registers for exit to interpreter. */
+    const BCIns *pc = snap_pc(&as->T->snapmap[snap->mapofs + snap->nent]);
+    int32_t mres;
+    if (bc_op(*pc) == BC_JLOOP) {  /* NYI: find a better way to do this. */
+      BCIns *retpc = &traceref(as->J, bc_d(*pc))->startins;
+      if (bc_isret(bc_op(*retpc)))
+	pc = retpc;
+    }
+#if LJ_GC64
+    emit_loadu64(as, RID_LPC, u64ptr(pc));
+#else
+    ra_allockreg(as, i32ptr(J2GG(as->J)->dispatch), RID_DISPATCH);
+    ra_allockreg(as, i32ptr(pc), RID_LPC);
+#endif
+    mres = (int32_t)(snap->nslots - baseslot - LJ_FR2);
+    switch (bc_op(*pc)) {
+    case BC_CALLM: case BC_CALLMT:
+      mres -= (int32_t)(1 + LJ_FR2 + bc_a(*pc) + bc_c(*pc)); break;
+    case BC_RETM: mres -= (int32_t)(bc_a(*pc) + bc_d(*pc)); break;
+    case BC_TSETM: mres -= (int32_t)bc_a(*pc); break;
+    default: if (bc_op(*pc) < BC_FUNCF) mres = 0; break;
+    }
+    ra_allockreg(as, mres, RID_RET);  /* Return MULTRES or 0. */
+  } else if (baseslot) {
+    /* Save modified BASE for linking to trace with higher start frame. */
+    emit_setgl(as, RID_BASE, jit_base);
+  }
+  emit_addptr(as, RID_BASE, 8*(int32_t)baseslot);
+
+  if (as->J->ktrace) {  /* Patch ktrace slot with the final GCtrace pointer. */
+    setgcref(IR(as->J->ktrace)[LJ_GC64].gcr, obj2gco(as->J->curfinal));
+    IR(as->J->ktrace)->o = IR_KGC;
+  }
+
+  /* Sync the interpreter state with the on-trace state. */
+  asm_stack_restore(as, snap);
+
+  /* Root traces that add frames need to check the stack at the end. */
+  if (!as->parent && gotframe)
+    asm_stack_check(as, as->topslot, NULL, as->freeset & RSET_GPR, snapno);
+}
+
+/* -- Trace setup --------------------------------------------------------- */
+
+/* Clear reg/sp for all instructions and add register hints. */
+static void asm_setup_regsp(ASMState *as)
+{
+  GCtrace *T = as->T;
+  int sink = T->sinktags;
+  IRRef nins = T->nins;
+  IRIns *ir, *lastir;
+  int inloop;
+#if LJ_TARGET_ARM
+  uint32_t rload = 0xa6402a64;
+#endif
+
+  ra_setup(as);
+#if LJ_TARGET_ARM64
+  ra_setkref(as, RID_GL, (intptr_t)J2G(as->J));
+#endif
+
+  /* Clear reg/sp for constants. */
+  for (ir = IR(T->nk), lastir = IR(REF_BASE); ir < lastir; ir++) {
+    ir->prev = REGSP_INIT;
+    if (irt_is64(ir->t) && ir->o != IR_KNULL) {
+#if LJ_GC64
+      /* The false-positive of irt_is64() for ASMREF_L (REF_NIL) is OK here. */
+      ir->i = 0;  /* Will become non-zero only for RIP-relative addresses. */
+#else
+      /* Make life easier for backends by putting address of constant in i. */
+      ir->i = (int32_t)(intptr_t)(ir+1);
+#endif
+      ir++;
+    }
+  }
+
+  /* REF_BASE is used for implicit references to the BASE register. */
+  lastir->prev = REGSP_HINT(RID_BASE);
+
+  as->snaprename = nins;
+  as->snapref = nins;
+  as->snapno = T->nsnap;
+  as->snapalloc = 0;
+
+  as->stopins = REF_BASE;
+  as->orignins = nins;
+  as->curins = nins;
+
+  /* Setup register hints for parent link instructions. */
+  ir = IR(REF_FIRST);
+  if (as->parent) {
+    uint16_t *p;
+    lastir = lj_snap_regspmap(as->J, as->parent, as->J->exitno, ir);
+    if (lastir - ir > LJ_MAX_JSLOTS)
+      lj_trace_err(as->J, LJ_TRERR_NYICOAL);
+    as->stopins = (IRRef)((lastir-1) - as->ir);
+    for (p = as->parentmap; ir < lastir; ir++) {
+      RegSP rs = ir->prev;
+      *p++ = (uint16_t)rs;  /* Copy original parent RegSP to parentmap. */
+      if (!ra_hasspill(regsp_spill(rs)))
+	ir->prev = (uint16_t)REGSP_HINT(regsp_reg(rs));
+      else
+	ir->prev = REGSP_INIT;
+    }
+  }
+
+  inloop = 0;
+  as->evenspill = SPS_FIRST;
+  for (lastir = IR(nins); ir < lastir; ir++) {
+    if (sink) {
+      if (ir->r == RID_SINK)
+	continue;
+      if (ir->r == RID_SUNK) {  /* Revert after ASM restart. */
+	ir->r = RID_SINK;
+	continue;
+      }
+    }
+    switch (ir->o) {
+    case IR_LOOP:
+      inloop = 1;
+      break;
+#if LJ_TARGET_ARM
+    case IR_SLOAD:
+      if (!((ir->op2 & IRSLOAD_TYPECHECK) || (ir+1)->o == IR_HIOP))
+	break;
+      /* fallthrough */
+    case IR_ALOAD: case IR_HLOAD: case IR_ULOAD: case IR_VLOAD:
+      if (!LJ_SOFTFP && irt_isnum(ir->t)) break;
+      ir->prev = (uint16_t)REGSP_HINT((rload & 15));
+      rload = lj_ror(rload, 4);
+      continue;
+    case IR_TMPREF:
+      if ((ir->op2 & IRTMPREF_OUT2) && as->evenspill < 4)
+	as->evenspill = 4;  /* TMPREF OUT2 needs two TValues on the stack. */
+      break;
+#endif
+    case IR_CALLXS: {
+      CCallInfo ci;
+      ci.flags = asm_callx_flags(as, ir);
+      ir->prev = asm_setup_call_slots(as, ir, &ci);
+      if (inloop)
+	as->modset |= RSET_SCRATCH;
+      continue;
+      }
+    case IR_CALLL:
+      /* lj_vm_next needs two TValues on the stack. */
+#if LJ_TARGET_X64 && LJ_ABI_WIN
+      if (ir->op2 == IRCALL_lj_vm_next && as->evenspill < SPS_FIRST + 4)
+	as->evenspill = SPS_FIRST + 4;
+#else
+      if (SPS_FIRST < 4 && ir->op2 == IRCALL_lj_vm_next && as->evenspill < 4)
+	as->evenspill = 4;
+#endif
+      /* fallthrough */
+    case IR_CALLN: case IR_CALLA: case IR_CALLS: {
+      const CCallInfo *ci = &lj_ir_callinfo[ir->op2];
+      ir->prev = asm_setup_call_slots(as, ir, ci);
+      if (inloop)
+	as->modset |= (ci->flags & CCI_NOFPRCLOBBER) ?
+		      (RSET_SCRATCH & ~RSET_FPR) : RSET_SCRATCH;
+      continue;
+      }
+    case IR_HIOP:
+      switch ((ir-1)->o) {
+#if LJ_SOFTFP && LJ_TARGET_ARM
+      case IR_SLOAD: case IR_ALOAD: case IR_HLOAD: case IR_ULOAD: case IR_VLOAD:
+	if (ra_hashint((ir-1)->r)) {
+	  ir->prev = (ir-1)->prev + 1;
+	  continue;
+	}
+	break;
+#endif
+#if !LJ_SOFTFP && LJ_NEED_FP64 && LJ_32 && LJ_HASFFI
+      case IR_CONV:
+	if (irt_isfp((ir-1)->t)) {
+	  ir->prev = REGSP_HINT(RID_FPRET);
+	  continue;
+	}
+#endif
+      /* fallthrough */
+      case IR_CALLN: case IR_CALLL: case IR_CALLS: case IR_CALLXS:
+#if LJ_SOFTFP
+      case IR_MIN: case IR_MAX:
+#endif
+	(ir-1)->prev = REGSP_HINT(RID_RETLO);
+	ir->prev = REGSP_HINT(RID_RETHI);
+	continue;
+      default:
+	break;
+      }
+      break;
+#if LJ_SOFTFP
+    case IR_MIN: case IR_MAX:
+      if ((ir+1)->o != IR_HIOP) break;
+#endif
+    /* fallthrough */
+    /* C calls evict all scratch regs and return results in RID_RET. */
+    case IR_SNEW: case IR_XSNEW: case IR_NEWREF: case IR_BUFPUT:
+      if (REGARG_NUMGPR < 3 && as->evenspill < 3)
+	as->evenspill = 3;  /* lj_str_new and lj_tab_newkey need 3 args. */
+#if LJ_TARGET_X86 && LJ_HASFFI
+      if (0) {
+    case IR_CNEW:
+	if (ir->op2 != REF_NIL && as->evenspill < 4)
+	  as->evenspill = 4;  /* lj_cdata_newv needs 4 args. */
+      }
+      /* fallthrough */
+#else
+      /* fallthrough */
+    case IR_CNEW:
+#endif
+      /* fallthrough */
+    case IR_TNEW: case IR_TDUP: case IR_CNEWI: case IR_TOSTR:
+    case IR_BUFSTR:
+      ir->prev = REGSP_HINT(RID_RET);
+      if (inloop)
+	as->modset = RSET_SCRATCH;
+      continue;
+    case IR_STRTO: case IR_OBAR:
+      if (inloop)
+	as->modset = RSET_SCRATCH;
+      break;
+#if !LJ_SOFTFP
+#if !LJ_TARGET_X86ORX64
+    case IR_LDEXP:
+#endif
+#endif
+      /* fallthrough */
+    case IR_POW:
+      if (!LJ_SOFTFP && irt_isnum(ir->t)) {
+	if (inloop)
+	  as->modset |= RSET_SCRATCH;
+#if LJ_TARGET_X86
+	if (irt_isnum(IR(ir->op2)->t)) {
+	  if (as->evenspill < 4)  /* Leave room to call pow(). */
+	    as->evenspill = 4;
+	}
+	break;
+#else
+	ir->prev = REGSP_HINT(RID_FPRET);
+	continue;
+#endif
+      }
+      /* fallthrough */ /* for integer POW */
+    case IR_DIV: case IR_MOD:
+      if ((LJ_64 && LJ_SOFTFP) || !irt_isnum(ir->t)) {
+	ir->prev = REGSP_HINT(RID_RET);
+	if (inloop)
+	  as->modset |= (RSET_SCRATCH & RSET_GPR);
+	continue;
+      }
+      break;
+#if LJ_64 && LJ_SOFTFP
+    case IR_ADD: case IR_SUB: case IR_MUL:
+      if (irt_isnum(ir->t)) {
+	ir->prev = REGSP_HINT(RID_RET);
+	if (inloop)
+	  as->modset |= (RSET_SCRATCH & RSET_GPR);
+	continue;
+      }
+      break;
+#endif
+    case IR_FPMATH:
+#if LJ_TARGET_X86ORX64
+      if (ir->op2 <= IRFPM_TRUNC) {
+	if (!(as->flags & JIT_F_SSE4_1)) {
+	  ir->prev = REGSP_HINT(RID_XMM0);
+	  if (inloop)
+	    as->modset |= RSET_RANGE(RID_XMM0, RID_XMM3+1)|RID2RSET(RID_EAX);
+	  continue;
+	}
+	break;
+      }
+#endif
+      if (inloop)
+	as->modset |= RSET_SCRATCH;
+#if LJ_TARGET_X86
+      break;
+#else
+      ir->prev = REGSP_HINT(RID_FPRET);
+      continue;
+#endif
+#if LJ_TARGET_X86ORX64
+    /* Non-constant shift counts need to be in RID_ECX on x86/x64. */
+    case IR_BSHL: case IR_BSHR: case IR_BSAR:
+      if ((as->flags & JIT_F_BMI2))  /* Except if BMI2 is available. */
+	break;
+      /* fallthrough */
+    case IR_BROL: case IR_BROR:
+      if (!irref_isk(ir->op2) && !ra_hashint(IR(ir->op2)->r)) {
+	IR(ir->op2)->r = REGSP_HINT(RID_ECX);
+	if (inloop)
+	  rset_set(as->modset, RID_ECX);
+      }
+      break;
+#endif
+    /* Do not propagate hints across type conversions or loads. */
+    case IR_TOBIT:
+    case IR_XLOAD:
+#if !LJ_TARGET_ARM
+    case IR_ALOAD: case IR_HLOAD: case IR_ULOAD: case IR_VLOAD:
+#endif
+      break;
+    case IR_CONV:
+      if (irt_isfp(ir->t) || (ir->op2 & IRCONV_SRCMASK) == IRT_NUM ||
+	  (ir->op2 & IRCONV_SRCMASK) == IRT_FLOAT)
+	break;
+      /* fallthrough */
+    default:
+      /* Propagate hints across likely 'op reg, imm' or 'op reg'. */
+      if (irref_isk(ir->op2) && !irref_isk(ir->op1) &&
+	  ra_hashint(regsp_reg(IR(ir->op1)->prev))) {
+	ir->prev = IR(ir->op1)->prev;
+	continue;
+      }
+      break;
+    }
+    ir->prev = REGSP_INIT;
+  }
+  if ((as->evenspill & 1))
+    as->oddspill = as->evenspill++;
+  else
+    as->oddspill = 0;
+}
+
+/* -- Assembler core ------------------------------------------------------ */
+
+/* Assemble a trace. */
+void lj_asm_trace(jit_State *J, GCtrace *T)
+{
+  ASMState as_;
+  ASMState *as = &as_;
+
+  /* Remove nops/renames left over from ASM restart due to LJ_TRERR_MCODELM. */
+  {
+    IRRef nins = T->nins;
+    IRIns *ir = &T->ir[nins-1];
+    if (ir->o == IR_NOP || ir->o == IR_RENAME) {
+      do { ir--; nins--; } while (ir->o == IR_NOP || ir->o == IR_RENAME);
+      T->nins = nins;
+    }
+  }
+
+  /* Ensure an initialized instruction beyond the last one for HIOP checks. */
+  /* This also allows one RENAME to be added without reallocating curfinal. */
+  as->orignins = lj_ir_nextins(J);
+  lj_ir_nop(&J->cur.ir[as->orignins]);
+
+  /* Setup initial state. Copy some fields to reduce indirections. */
+  as->J = J;
+  as->T = T;
+  J->curfinal = lj_trace_alloc(J->L, T);  /* This copies the IR, too. */
+  as->flags = J->flags;
+  as->loopref = J->loopref;
+  as->realign = NULL;
+  as->loopinv = 0;
+  as->parent = J->parent ? traceref(J, J->parent) : NULL;
+
+  /* Reserve MCode memory. */
+  as->mctop = as->mctoporig = lj_mcode_reserve(J, &as->mcbot);
+  as->mcp = as->mctop;
+  as->mclim = as->mcbot + MCLIM_REDZONE;
+  asm_setup_target(as);
+
+  /*
+  ** This is a loop, because the MCode may have to be (re-)assembled
+  ** multiple times:
+  **
+  ** 1. as->realign is set (and the assembly aborted), if the arch-specific
+  **    backend wants the MCode to be aligned differently.
+  **
+  **    This is currently only the case on x86/x64, where small loops get
+  **    an aligned loop body plus a short branch. Not much effort is wasted,
+  **    because the abort happens very quickly and only once.
+  **
+  ** 2. The IR is immovable, since the MCode embeds pointers to various
+  **    constants inside the IR. But RENAMEs may need to be added to the IR
+  **    during assembly, which might grow and reallocate the IR. We check
+  **    at the end if the IR (in J->cur.ir) has actually grown, resize the
+  **    copy (in J->curfinal.ir) and try again.
+  **
+  **    95% of all traces have zero RENAMEs, 3% have one RENAME, 1.5% have
+  **    2 RENAMEs and only 0.5% have more than that. That's why we opt to
+  **    always have one spare slot in the IR (see above), which means we
+  **    have to redo the assembly for only ~2% of all traces.
+  **
+  **    Very, very rarely, this needs to be done repeatedly, since the
+  **    location of constants inside the IR (actually, reachability from
+  **    a global pointer) may affect register allocation and thus the
+  **    number of RENAMEs.
+  */
+  for (;;) {
+    as->mcp = as->mctop;
+#ifdef LUA_USE_ASSERT
+    as->mcp_prev = as->mcp;
+#endif
+    as->ir = J->curfinal->ir;  /* Use the copied IR. */
+    as->curins = J->cur.nins = as->orignins;
+
+    RA_DBG_START();
+    RA_DBGX((as, "===== STOP ====="));
+
+    /* General trace setup. Emit tail of trace. */
+    asm_tail_prep(as);
+    as->mcloop = NULL;
+    as->flagmcp = NULL;
+    as->topslot = 0;
+    as->gcsteps = 0;
+    as->sectref = as->loopref;
+    as->fuseref = (as->flags & JIT_F_OPT_FUSE) ? as->loopref : FUSE_DISABLED;
+    asm_setup_regsp(as);
+    if (!as->loopref)
+      asm_tail_link(as);
+
+    /* Assemble a trace in linear backwards order. */
+    for (as->curins--; as->curins > as->stopins; as->curins--) {
+      IRIns *ir = IR(as->curins);
+      /* 64 bit types handled by SPLIT for 32 bit archs. */
+      lj_assertA(!(LJ_32 && irt_isint64(ir->t)),
+		 "IR %04d has unsplit 64 bit type",
+		 (int)(ir - as->ir) - REF_BIAS);
+      asm_snap_prev(as);
+      if (!ra_used(ir) && !ir_sideeff(ir) && (as->flags & JIT_F_OPT_DCE))
+	continue;  /* Dead-code elimination can be soooo easy. */
+      if (irt_isguard(ir->t))
+	asm_snap_prep(as);
+      RA_DBG_REF();
+      checkmclim(as);
+      asm_ir(as, ir);
+    }
+
+    if (as->realign && J->curfinal->nins >= T->nins)
+      continue;  /* Retry in case only the MCode needs to be realigned. */
+
+    /* Emit head of trace. */
+    RA_DBG_REF();
+    checkmclim(as);
+    if (as->gcsteps > 0) {
+      as->curins = as->T->snap[0].ref;
+      asm_snap_prep(as);  /* The GC check is a guard. */
+      asm_gc_check(as);
+      as->curins = as->stopins;
+    }
+    ra_evictk(as);
+    if (as->parent)
+      asm_head_side(as);
+    else
+      asm_head_root(as);
+    asm_phi_fixup(as);
+
+    if (J->curfinal->nins >= T->nins) {  /* IR didn't grow? */
+      lj_assertA(J->curfinal->nk == T->nk, "unexpected IR constant growth");
+      memcpy(J->curfinal->ir + as->orignins, T->ir + as->orignins,
+	     (T->nins - as->orignins) * sizeof(IRIns));  /* Copy RENAMEs. */
+      T->nins = J->curfinal->nins;
+      /* Fill mcofs of any unprocessed snapshots. */
+      as->curins = REF_FIRST;
+      asm_snap_prev(as);
+      break;  /* Done. */
+    }
+
+    /* Otherwise try again with a bigger IR. */
+    lj_trace_free(J2G(J), J->curfinal);
+    J->curfinal = NULL;  /* In case lj_trace_alloc() OOMs. */
+    J->curfinal = lj_trace_alloc(J->L, T);
+    as->realign = NULL;
+  }
+
+  RA_DBGX((as, "===== START ===="));
+  RA_DBG_FLUSH();
+  if (as->freeset != RSET_ALL)
+    lj_trace_err(as->J, LJ_TRERR_BADRA);  /* Ouch! Should never happen. */
+
+  /* Set trace entry point before fixing up tail to allow link to self. */
+  T->mcode = as->mcp;
+  T->mcloop = as->mcloop ? (MSize)((char *)as->mcloop - (char *)as->mcp) : 0;
+  if (as->loopref)
+    asm_loop_tail_fixup(as);
+  else
+    asm_tail_fixup(as, T->link);  /* Note: this may change as->mctop! */
+  T->szmcode = (MSize)((char *)as->mctop - (char *)as->mcp);
+  asm_snap_fixup_mcofs(as);
+#if LJ_TARGET_MCODE_FIXUP
+  asm_mcode_fixup(T->mcode, T->szmcode);
+#endif
+  lj_mcode_sync(T->mcode, as->mctoporig);
+}
+
+#undef IR
+
+#endif