Adding upstream version 1.20.14.upstream/1.20.14upstream

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

1 files changed, 802 insertions, 0 deletions

diff --git a/src/cmd/internal/obj/s390x/objz.go b/src/cmd/internal/obj/s390x/objz.go
new file mode 100644
index 0000000..4e84756
--- /dev/null
+++ b/src/cmd/internal/obj/s390x/objz.go
@@ -0,0 +1,802 @@
+// Based on cmd/internal/obj/ppc64/obj9.go.
+//
+//	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
+//	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
+//	Portions Copyright © 1997-1999 Vita Nuova Limited
+//	Portions Copyright © 2000-2008 Vita Nuova Holdings Limited (www.vitanuova.com)
+//	Portions Copyright © 2004,2006 Bruce Ellis
+//	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
+//	Revisions Copyright © 2000-2008 Lucent Technologies Inc. and others
+//	Portions Copyright © 2009 The Go Authors. All rights reserved.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package s390x
+
+import (
+	"cmd/internal/obj"
+	"cmd/internal/objabi"
+	"cmd/internal/sys"
+	"log"
+	"math"
+)
+
+func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
+	p.From.Class = 0
+	p.To.Class = 0
+
+	c := ctxtz{ctxt: ctxt, newprog: newprog}
+
+	// Rewrite BR/BL to symbol as TYPE_BRANCH.
+	switch p.As {
+	case ABR, ABL, obj.ARET, obj.ADUFFZERO, obj.ADUFFCOPY:
+		if p.To.Sym != nil {
+			p.To.Type = obj.TYPE_BRANCH
+		}
+	}
+
+	// Rewrite float constants to values stored in memory unless they are +0.
+	switch p.As {
+	case AFMOVS:
+		if p.From.Type == obj.TYPE_FCONST {
+			f32 := float32(p.From.Val.(float64))
+			if math.Float32bits(f32) == 0 { // +0
+				break
+			}
+			p.From.Type = obj.TYPE_MEM
+			p.From.Sym = ctxt.Float32Sym(f32)
+			p.From.Name = obj.NAME_EXTERN
+			p.From.Offset = 0
+		}
+
+	case AFMOVD:
+		if p.From.Type == obj.TYPE_FCONST {
+			f64 := p.From.Val.(float64)
+			if math.Float64bits(f64) == 0 { // +0
+				break
+			}
+			p.From.Type = obj.TYPE_MEM
+			p.From.Sym = ctxt.Float64Sym(f64)
+			p.From.Name = obj.NAME_EXTERN
+			p.From.Offset = 0
+		}
+
+		// put constants not loadable by LOAD IMMEDIATE into memory
+	case AMOVD:
+		if p.From.Type == obj.TYPE_CONST {
+			val := p.From.Offset
+			if int64(int32(val)) != val &&
+				int64(uint32(val)) != val &&
+				int64(uint64(val)&(0xffffffff<<32)) != val {
+				p.From.Type = obj.TYPE_MEM
+				p.From.Sym = ctxt.Int64Sym(p.From.Offset)
+				p.From.Name = obj.NAME_EXTERN
+				p.From.Offset = 0
+			}
+		}
+	}
+
+	// Rewrite SUB constants into ADD.
+	switch p.As {
+	case ASUBC:
+		if p.From.Type == obj.TYPE_CONST && isint32(-p.From.Offset) {
+			p.From.Offset = -p.From.Offset
+			p.As = AADDC
+		}
+
+	case ASUB:
+		if p.From.Type == obj.TYPE_CONST && isint32(-p.From.Offset) {
+			p.From.Offset = -p.From.Offset
+			p.As = AADD
+		}
+	}
+
+	if c.ctxt.Flag_dynlink {
+		c.rewriteToUseGot(p)
+	}
+}
+
+// Rewrite p, if necessary, to access global data via the global offset table.
+func (c *ctxtz) rewriteToUseGot(p *obj.Prog) {
+	// At the moment EXRL instructions are not emitted by the compiler and only reference local symbols in
+	// assembly code.
+	if p.As == AEXRL {
+		return
+	}
+
+	// We only care about global data: NAME_EXTERN means a global
+	// symbol in the Go sense, and p.Sym.Local is true for a few
+	// internally defined symbols.
+	// Rewrites must not clobber flags and therefore cannot use the
+	// ADD instruction.
+	if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
+		// MOVD $sym, Rx becomes MOVD sym@GOT, Rx
+		// MOVD $sym+<off>, Rx becomes MOVD sym@GOT, Rx or REGTMP2; MOVD $<off>(Rx or REGTMP2), Rx
+		if p.To.Type != obj.TYPE_REG || p.As != AMOVD {
+			c.ctxt.Diag("do not know how to handle LEA-type insn to non-register in %v with -dynlink", p)
+		}
+		p.From.Type = obj.TYPE_MEM
+		p.From.Name = obj.NAME_GOTREF
+		q := p
+		if p.From.Offset != 0 {
+			target := p.To.Reg
+			if target == REG_R0 {
+				// Cannot use R0 as input to address calculation.
+				// REGTMP might be used by the assembler.
+				p.To.Reg = REGTMP2
+			}
+			q = obj.Appendp(q, c.newprog)
+			q.As = AMOVD
+			q.From.Type = obj.TYPE_ADDR
+			q.From.Offset = p.From.Offset
+			q.From.Reg = p.To.Reg
+			q.To.Type = obj.TYPE_REG
+			q.To.Reg = target
+			p.From.Offset = 0
+		}
+	}
+	if p.GetFrom3() != nil && p.GetFrom3().Name == obj.NAME_EXTERN {
+		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
+	}
+	var source *obj.Addr
+	// MOVD sym, Ry becomes MOVD sym@GOT, REGTMP2; MOVD (REGTMP2), Ry
+	// MOVD Ry, sym becomes MOVD sym@GOT, REGTMP2; MOVD Ry, (REGTMP2)
+	// An addition may be inserted between the two MOVs if there is an offset.
+	if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
+		if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
+			c.ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
+		}
+		source = &p.From
+	} else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
+		source = &p.To
+	} else {
+		return
+	}
+	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
+		return
+	}
+	if source.Sym.Type == objabi.STLSBSS {
+		return
+	}
+	if source.Type != obj.TYPE_MEM {
+		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
+	}
+	p1 := obj.Appendp(p, c.newprog)
+	p2 := obj.Appendp(p1, c.newprog)
+
+	p1.As = AMOVD
+	p1.From.Type = obj.TYPE_MEM
+	p1.From.Sym = source.Sym
+	p1.From.Name = obj.NAME_GOTREF
+	p1.To.Type = obj.TYPE_REG
+	p1.To.Reg = REGTMP2
+
+	p2.As = p.As
+	p2.From = p.From
+	p2.To = p.To
+	if p.From.Name == obj.NAME_EXTERN {
+		p2.From.Reg = REGTMP2
+		p2.From.Name = obj.NAME_NONE
+		p2.From.Sym = nil
+	} else if p.To.Name == obj.NAME_EXTERN {
+		p2.To.Reg = REGTMP2
+		p2.To.Name = obj.NAME_NONE
+		p2.To.Sym = nil
+	} else {
+		return
+	}
+	obj.Nopout(p)
+}
+
+func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
+	// TODO(minux): add morestack short-cuts with small fixed frame-size.
+	if cursym.Func().Text == nil || cursym.Func().Text.Link == nil {
+		return
+	}
+
+	c := ctxtz{ctxt: ctxt, cursym: cursym, newprog: newprog}
+
+	p := c.cursym.Func().Text
+	textstksiz := p.To.Offset
+	if textstksiz == -8 {
+		// Compatibility hack.
+		p.From.Sym.Set(obj.AttrNoFrame, true)
+		textstksiz = 0
+	}
+	if textstksiz%8 != 0 {
+		c.ctxt.Diag("frame size %d not a multiple of 8", textstksiz)
+	}
+	if p.From.Sym.NoFrame() {
+		if textstksiz != 0 {
+			c.ctxt.Diag("NOFRAME functions must have a frame size of 0, not %d", textstksiz)
+		}
+	}
+
+	c.cursym.Func().Args = p.To.Val.(int32)
+	c.cursym.Func().Locals = int32(textstksiz)
+
+	/*
+	 * find leaf subroutines
+	 * strip NOPs
+	 * expand RET
+	 */
+
+	var q *obj.Prog
+	for p := c.cursym.Func().Text; p != nil; p = p.Link {
+		switch p.As {
+		case obj.ATEXT:
+			q = p
+			p.Mark |= LEAF
+
+		case ABL, ABCL:
+			q = p
+			c.cursym.Func().Text.Mark &^= LEAF
+			fallthrough
+
+		case ABC,
+			ABRC,
+			ABEQ,
+			ABGE,
+			ABGT,
+			ABLE,
+			ABLT,
+			ABLEU,
+			ABLTU,
+			ABNE,
+			ABR,
+			ABVC,
+			ABVS,
+			ACRJ,
+			ACGRJ,
+			ACLRJ,
+			ACLGRJ,
+			ACIJ,
+			ACGIJ,
+			ACLIJ,
+			ACLGIJ,
+			ACMPBEQ,
+			ACMPBGE,
+			ACMPBGT,
+			ACMPBLE,
+			ACMPBLT,
+			ACMPBNE,
+			ACMPUBEQ,
+			ACMPUBGE,
+			ACMPUBGT,
+			ACMPUBLE,
+			ACMPUBLT,
+			ACMPUBNE:
+			q = p
+			p.Mark |= BRANCH
+
+		default:
+			q = p
+		}
+	}
+
+	autosize := int32(0)
+	var pLast *obj.Prog
+	var pPre *obj.Prog
+	var pPreempt *obj.Prog
+	var pCheck *obj.Prog
+	wasSplit := false
+	for p := c.cursym.Func().Text; p != nil; p = p.Link {
+		pLast = p
+		switch p.As {
+		case obj.ATEXT:
+			autosize = int32(textstksiz)
+
+			if p.Mark&LEAF != 0 && autosize == 0 {
+				// A leaf function with no locals has no frame.
+				p.From.Sym.Set(obj.AttrNoFrame, true)
+			}
+
+			if !p.From.Sym.NoFrame() {
+				// If there is a stack frame at all, it includes
+				// space to save the LR.
+				autosize += int32(c.ctxt.Arch.FixedFrameSize)
+			}
+
+			if p.Mark&LEAF != 0 && autosize < objabi.StackSmall {
+				// A leaf function with a small stack can be marked
+				// NOSPLIT, avoiding a stack check.
+				p.From.Sym.Set(obj.AttrNoSplit, true)
+			}
+
+			p.To.Offset = int64(autosize)
+
+			q := p
+
+			if !p.From.Sym.NoSplit() {
+				p, pPreempt, pCheck = c.stacksplitPre(p, autosize) // emit pre part of split check
+				pPre = p
+				p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
+				wasSplit = true //need post part of split
+			}
+
+			if autosize != 0 {
+				// Make sure to save link register for non-empty frame, even if
+				// it is a leaf function, so that traceback works.
+				// Store link register before decrementing SP, so if a signal comes
+				// during the execution of the function prologue, the traceback
+				// code will not see a half-updated stack frame.
+				// This sequence is not async preemptible, as if we open a frame
+				// at the current SP, it will clobber the saved LR.
+				q = c.ctxt.StartUnsafePoint(p, c.newprog)
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = AMOVD
+				q.From.Type = obj.TYPE_REG
+				q.From.Reg = REG_LR
+				q.To.Type = obj.TYPE_MEM
+				q.To.Reg = REGSP
+				q.To.Offset = int64(-autosize)
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = AMOVD
+				q.From.Type = obj.TYPE_ADDR
+				q.From.Offset = int64(-autosize)
+				q.From.Reg = REGSP // not actually needed - REGSP is assumed if no reg is provided
+				q.To.Type = obj.TYPE_REG
+				q.To.Reg = REGSP
+				q.Spadj = autosize
+
+				q = c.ctxt.EndUnsafePoint(q, c.newprog, -1)
+
+				// On Linux, in a cgo binary we may get a SIGSETXID signal early on
+				// before the signal stack is set, as glibc doesn't allow us to block
+				// SIGSETXID. So a signal may land on the current stack and clobber
+				// the content below the SP. We store the LR again after the SP is
+				// decremented.
+				q = obj.Appendp(q, c.newprog)
+				q.As = AMOVD
+				q.From.Type = obj.TYPE_REG
+				q.From.Reg = REG_LR
+				q.To.Type = obj.TYPE_MEM
+				q.To.Reg = REGSP
+				q.To.Offset = 0
+			} else if c.cursym.Func().Text.Mark&LEAF == 0 {
+				// A very few functions that do not return to their caller
+				// (e.g. gogo) are not identified as leaves but still have
+				// no frame.
+				c.cursym.Func().Text.Mark |= LEAF
+			}
+
+			if c.cursym.Func().Text.Mark&LEAF != 0 {
+				c.cursym.Set(obj.AttrLeaf, true)
+				break
+			}
+
+			if c.cursym.Func().Text.From.Sym.Wrapper() {
+				// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
+				//
+				//	MOVD g_panic(g), R3
+				//	CMP R3, $0
+				//	BEQ end
+				//	MOVD panic_argp(R3), R4
+				//	ADD $(autosize+8), R1, R5
+				//	CMP R4, R5
+				//	BNE end
+				//	ADD $8, R1, R6
+				//	MOVD R6, panic_argp(R3)
+				// end:
+				//	NOP
+				//
+				// The NOP is needed to give the jumps somewhere to land.
+				// It is a liblink NOP, not a s390x NOP: it encodes to 0 instruction bytes.
+
+				q = obj.Appendp(q, c.newprog)
+
+				q.As = AMOVD
+				q.From.Type = obj.TYPE_MEM
+				q.From.Reg = REGG
+				q.From.Offset = 4 * int64(c.ctxt.Arch.PtrSize) // G.panic
+				q.To.Type = obj.TYPE_REG
+				q.To.Reg = REG_R3
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = ACMP
+				q.From.Type = obj.TYPE_REG
+				q.From.Reg = REG_R3
+				q.To.Type = obj.TYPE_CONST
+				q.To.Offset = 0
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = ABEQ
+				q.To.Type = obj.TYPE_BRANCH
+				p1 := q
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = AMOVD
+				q.From.Type = obj.TYPE_MEM
+				q.From.Reg = REG_R3
+				q.From.Offset = 0 // Panic.argp
+				q.To.Type = obj.TYPE_REG
+				q.To.Reg = REG_R4
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = AADD
+				q.From.Type = obj.TYPE_CONST
+				q.From.Offset = int64(autosize) + c.ctxt.Arch.FixedFrameSize
+				q.Reg = REGSP
+				q.To.Type = obj.TYPE_REG
+				q.To.Reg = REG_R5
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = ACMP
+				q.From.Type = obj.TYPE_REG
+				q.From.Reg = REG_R4
+				q.To.Type = obj.TYPE_REG
+				q.To.Reg = REG_R5
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = ABNE
+				q.To.Type = obj.TYPE_BRANCH
+				p2 := q
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = AADD
+				q.From.Type = obj.TYPE_CONST
+				q.From.Offset = c.ctxt.Arch.FixedFrameSize
+				q.Reg = REGSP
+				q.To.Type = obj.TYPE_REG
+				q.To.Reg = REG_R6
+
+				q = obj.Appendp(q, c.newprog)
+				q.As = AMOVD
+				q.From.Type = obj.TYPE_REG
+				q.From.Reg = REG_R6
+				q.To.Type = obj.TYPE_MEM
+				q.To.Reg = REG_R3
+				q.To.Offset = 0 // Panic.argp
+
+				q = obj.Appendp(q, c.newprog)
+
+				q.As = obj.ANOP
+				p1.To.SetTarget(q)
+				p2.To.SetTarget(q)
+			}
+
+		case obj.ARET:
+			retTarget := p.To.Sym
+
+			if c.cursym.Func().Text.Mark&LEAF != 0 {
+				if autosize == 0 {
+					p.As = ABR
+					p.From = obj.Addr{}
+					if retTarget == nil {
+						p.To.Type = obj.TYPE_REG
+						p.To.Reg = REG_LR
+					} else {
+						p.To.Type = obj.TYPE_BRANCH
+						p.To.Sym = retTarget
+					}
+					p.Mark |= BRANCH
+					break
+				}
+
+				p.As = AADD
+				p.From.Type = obj.TYPE_CONST
+				p.From.Offset = int64(autosize)
+				p.To.Type = obj.TYPE_REG
+				p.To.Reg = REGSP
+				p.Spadj = -autosize
+
+				q = obj.Appendp(p, c.newprog)
+				q.As = ABR
+				q.From = obj.Addr{}
+				if retTarget == nil {
+					q.To.Type = obj.TYPE_REG
+					q.To.Reg = REG_LR
+				} else {
+					q.To.Type = obj.TYPE_BRANCH
+					q.To.Sym = retTarget
+				}
+				q.Mark |= BRANCH
+				q.Spadj = autosize
+				break
+			}
+
+			p.As = AMOVD
+			p.From.Type = obj.TYPE_MEM
+			p.From.Reg = REGSP
+			p.From.Offset = 0
+			p.To = obj.Addr{
+				Type: obj.TYPE_REG,
+				Reg:  REG_LR,
+			}
+
+			q = p
+
+			if autosize != 0 {
+				q = obj.Appendp(q, c.newprog)
+				q.As = AADD
+				q.From.Type = obj.TYPE_CONST
+				q.From.Offset = int64(autosize)
+				q.To.Type = obj.TYPE_REG
+				q.To.Reg = REGSP
+				q.Spadj = -autosize
+			}
+
+			q = obj.Appendp(q, c.newprog)
+			q.As = ABR
+			q.From = obj.Addr{}
+			if retTarget == nil {
+				q.To.Type = obj.TYPE_REG
+				q.To.Reg = REG_LR
+			} else {
+				q.To.Type = obj.TYPE_BRANCH
+				q.To.Sym = retTarget
+			}
+			q.Mark |= BRANCH
+			q.Spadj = autosize
+
+		case AADD:
+			if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
+				p.Spadj = int32(-p.From.Offset)
+			}
+
+		case obj.AGETCALLERPC:
+			if cursym.Leaf() {
+				/* MOVD LR, Rd */
+				p.As = AMOVD
+				p.From.Type = obj.TYPE_REG
+				p.From.Reg = REG_LR
+			} else {
+				/* MOVD (RSP), Rd */
+				p.As = AMOVD
+				p.From.Type = obj.TYPE_MEM
+				p.From.Reg = REGSP
+			}
+		}
+
+		if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.Spadj == 0 {
+			f := c.cursym.Func()
+			if f.FuncFlag&objabi.FuncFlag_SPWRITE == 0 {
+				c.cursym.Func().FuncFlag |= objabi.FuncFlag_SPWRITE
+				if ctxt.Debugvlog || !ctxt.IsAsm {
+					ctxt.Logf("auto-SPWRITE: %s\n", c.cursym.Name)
+					if !ctxt.IsAsm {
+						ctxt.Diag("invalid auto-SPWRITE in non-assembly")
+						ctxt.DiagFlush()
+						log.Fatalf("bad SPWRITE")
+					}
+				}
+			}
+		}
+	}
+	if wasSplit {
+		c.stacksplitPost(pLast, pPre, pPreempt, pCheck, autosize) // emit post part of split check
+	}
+}
+
+// stacksplitPre generates the function stack check prologue following
+// Prog p (which should be the TEXT Prog). It returns one or two
+// branch Progs that must be patched to jump to the morestack epilogue,
+// and the Prog that starts the morestack check.
+func (c *ctxtz) stacksplitPre(p *obj.Prog, framesize int32) (pPre, pPreempt, pCheck *obj.Prog) {
+	if c.ctxt.Flag_maymorestack != "" {
+		// Save LR and REGCTXT
+		const frameSize = 16
+		p = c.ctxt.StartUnsafePoint(p, c.newprog)
+		// MOVD LR, -16(SP)
+		p = obj.Appendp(p, c.newprog)
+		p.As = AMOVD
+		p.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_LR}
+		p.To = obj.Addr{Type: obj.TYPE_MEM, Reg: REGSP, Offset: -frameSize}
+		// MOVD $-16(SP), SP
+		p = obj.Appendp(p, c.newprog)
+		p.As = AMOVD
+		p.From = obj.Addr{Type: obj.TYPE_ADDR, Offset: -frameSize, Reg: REGSP}
+		p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REGSP}
+		p.Spadj = frameSize
+		// MOVD REGCTXT, 8(SP)
+		p = obj.Appendp(p, c.newprog)
+		p.As = AMOVD
+		p.From = obj.Addr{Type: obj.TYPE_REG, Reg: REGCTXT}
+		p.To = obj.Addr{Type: obj.TYPE_MEM, Reg: REGSP, Offset: 8}
+
+		// BL maymorestack
+		p = obj.Appendp(p, c.newprog)
+		p.As = ABL
+		// See ../x86/obj6.go
+		sym := c.ctxt.LookupABI(c.ctxt.Flag_maymorestack, c.cursym.ABI())
+		p.To = obj.Addr{Type: obj.TYPE_BRANCH, Sym: sym}
+
+		// Restore LR and REGCTXT
+
+		// MOVD REGCTXT, 8(SP)
+		p = obj.Appendp(p, c.newprog)
+		p.As = AMOVD
+		p.From = obj.Addr{Type: obj.TYPE_MEM, Reg: REGSP, Offset: 8}
+		p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REGCTXT}
+		// MOVD (SP), LR
+		p = obj.Appendp(p, c.newprog)
+		p.As = AMOVD
+		p.From = obj.Addr{Type: obj.TYPE_MEM, Reg: REGSP, Offset: 0}
+		p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_LR}
+		// MOVD $16(SP), SP
+		p = obj.Appendp(p, c.newprog)
+		p.As = AMOVD
+		p.From = obj.Addr{Type: obj.TYPE_CONST, Reg: REGSP, Offset: frameSize}
+		p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REGSP}
+		p.Spadj = -frameSize
+
+		p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
+	}
+
+	// MOVD	g_stackguard(g), R3
+	p = obj.Appendp(p, c.newprog)
+	// Jump back to here after morestack returns.
+	pCheck = p
+
+	p.As = AMOVD
+	p.From.Type = obj.TYPE_MEM
+	p.From.Reg = REGG
+	p.From.Offset = 2 * int64(c.ctxt.Arch.PtrSize) // G.stackguard0
+	if c.cursym.CFunc() {
+		p.From.Offset = 3 * int64(c.ctxt.Arch.PtrSize) // G.stackguard1
+	}
+	p.To.Type = obj.TYPE_REG
+	p.To.Reg = REG_R3
+
+	// Mark the stack bound check and morestack call async nonpreemptible.
+	// If we get preempted here, when resumed the preemption request is
+	// cleared, but we'll still call morestack, which will double the stack
+	// unnecessarily. See issue #35470.
+	p = c.ctxt.StartUnsafePoint(p, c.newprog)
+
+	if framesize <= objabi.StackSmall {
+		// small stack: SP < stackguard
+		//	CMPUBGE	stackguard, SP, label-of-call-to-morestack
+
+		p = obj.Appendp(p, c.newprog)
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REG_R3
+		p.Reg = REGSP
+		p.As = ACMPUBGE
+		p.To.Type = obj.TYPE_BRANCH
+
+		return p, nil, pCheck
+	}
+
+	// large stack: SP-framesize < stackguard-StackSmall
+
+	offset := int64(framesize) - objabi.StackSmall
+	if framesize > objabi.StackBig {
+		// Such a large stack we need to protect against underflow.
+		// The runtime guarantees SP > objabi.StackBig, but
+		// framesize is large enough that SP-framesize may
+		// underflow, causing a direct comparison with the
+		// stack guard to incorrectly succeed. We explicitly
+		// guard against underflow.
+		//
+		//	MOVD	$(framesize-StackSmall), R4
+		//	CMPUBLT	SP, R4, label-of-call-to-morestack
+
+		p = obj.Appendp(p, c.newprog)
+		p.As = AMOVD
+		p.From.Type = obj.TYPE_CONST
+		p.From.Offset = offset
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = REG_R4
+
+		p = obj.Appendp(p, c.newprog)
+		pPreempt = p
+		p.As = ACMPUBLT
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = REGSP
+		p.Reg = REG_R4
+		p.To.Type = obj.TYPE_BRANCH
+	}
+
+	// Check against the stack guard. We've ensured this won't underflow.
+	//	ADD $-(framesize-StackSmall), SP, R4
+	//	CMPUBGE stackguard, R4, label-of-call-to-morestack
+	p = obj.Appendp(p, c.newprog)
+	p.As = AADD
+	p.From.Type = obj.TYPE_CONST
+	p.From.Offset = -offset
+	p.Reg = REGSP
+	p.To.Type = obj.TYPE_REG
+	p.To.Reg = REG_R4
+
+	p = obj.Appendp(p, c.newprog)
+	p.From.Type = obj.TYPE_REG
+	p.From.Reg = REG_R3
+	p.Reg = REG_R4
+	p.As = ACMPUBGE
+	p.To.Type = obj.TYPE_BRANCH
+
+	return p, pPreempt, pCheck
+}
+
+// stacksplitPost generates the function epilogue that calls morestack
+// and returns the new last instruction in the function.
+//
+// p is the last Prog in the function. pPre and pPreempt, if non-nil,
+// are the instructions that branch to the epilogue. This will fill in
+// their branch targets. pCheck is the Prog that begins the stack check.
+func (c *ctxtz) stacksplitPost(p *obj.Prog, pPre, pPreempt, pCheck *obj.Prog, framesize int32) *obj.Prog {
+	// Now we are at the end of the function, but logically
+	// we are still in function prologue. We need to fix the
+	// SP data and PCDATA.
+	spfix := obj.Appendp(p, c.newprog)
+	spfix.As = obj.ANOP
+	spfix.Spadj = -framesize
+
+	pcdata := c.ctxt.EmitEntryStackMap(c.cursym, spfix, c.newprog)
+	pcdata = c.ctxt.StartUnsafePoint(pcdata, c.newprog)
+
+	// MOVD	LR, R5
+	p = obj.Appendp(pcdata, c.newprog)
+	pPre.To.SetTarget(p)
+	p.As = AMOVD
+	p.From.Type = obj.TYPE_REG
+	p.From.Reg = REG_LR
+	p.To.Type = obj.TYPE_REG
+	p.To.Reg = REG_R5
+	if pPreempt != nil {
+		pPreempt.To.SetTarget(p)
+	}
+
+	// BL	runtime.morestack(SB)
+	p = obj.Appendp(p, c.newprog)
+
+	p.As = ABL
+	p.To.Type = obj.TYPE_BRANCH
+	if c.cursym.CFunc() {
+		p.To.Sym = c.ctxt.Lookup("runtime.morestackc")
+	} else if !c.cursym.Func().Text.From.Sym.NeedCtxt() {
+		p.To.Sym = c.ctxt.Lookup("runtime.morestack_noctxt")
+	} else {
+		p.To.Sym = c.ctxt.Lookup("runtime.morestack")
+	}
+
+	p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
+
+	// BR	pCheck
+	p = obj.Appendp(p, c.newprog)
+
+	p.As = ABR
+	p.To.Type = obj.TYPE_BRANCH
+	p.To.SetTarget(pCheck)
+	return p
+}
+
+var unaryDst = map[obj.As]bool{
+	ASTCK:  true,
+	ASTCKC: true,
+	ASTCKE: true,
+	ASTCKF: true,
+	ANEG:   true,
+	ANEGW:  true,
+	AVONE:  true,
+	AVZERO: true,
+}
+
+var Links390x = obj.LinkArch{
+	Arch:           sys.ArchS390X,
+	Init:           buildop,
+	Preprocess:     preprocess,
+	Assemble:       spanz,
+	Progedit:       progedit,
+	UnaryDst:       unaryDst,
+	DWARFRegisters: S390XDWARFRegisters,
+}