1 files changed, 291 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssagen/pgen.go b/src/cmd/compile/internal/ssagen/pgen.go
new file mode 100644
index 0000000..86d40e2
--- /dev/null
+++ b/src/cmd/compile/internal/ssagen/pgen.go
@@ -0,0 +1,291 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssagen
+
+import (
+	"internal/buildcfg"
+	"internal/race"
+	"math/rand"
+	"sort"
+	"sync"
+	"time"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/objw"
+	"cmd/compile/internal/ssa"
+	"cmd/compile/internal/types"
+	"cmd/internal/obj"
+	"cmd/internal/objabi"
+	"cmd/internal/src"
+)
+
+// cmpstackvarlt reports whether the stack variable a sorts before b.
+//
+// Sort the list of stack variables. Autos after anything else,
+// within autos, unused after used, within used, things with
+// pointers first, zeroed things first, and then decreasing size.
+// Because autos are laid out in decreasing addresses
+// on the stack, pointers first, zeroed things first and decreasing size
+// really means, in memory, things with pointers needing zeroing at
+// the top of the stack and increasing in size.
+// Non-autos sort on offset.
+func cmpstackvarlt(a, b *ir.Name) bool {
+	if needAlloc(a) != needAlloc(b) {
+		return needAlloc(b)
+	}
+
+	if !needAlloc(a) {
+		return a.FrameOffset() < b.FrameOffset()
+	}
+
+	if a.Used() != b.Used() {
+		return a.Used()
+	}
+
+	ap := a.Type().HasPointers()
+	bp := b.Type().HasPointers()
+	if ap != bp {
+		return ap
+	}
+
+	ap = a.Needzero()
+	bp = b.Needzero()
+	if ap != bp {
+		return ap
+	}
+
+	if a.Type().Size() != b.Type().Size() {
+		return a.Type().Size() > b.Type().Size()
+	}
+
+	return a.Sym().Name < b.Sym().Name
+}
+
+// byStackvar implements sort.Interface for []*Node using cmpstackvarlt.
+type byStackVar []*ir.Name
+
+func (s byStackVar) Len() int           { return len(s) }
+func (s byStackVar) Less(i, j int) bool { return cmpstackvarlt(s[i], s[j]) }
+func (s byStackVar) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+// needAlloc reports whether n is within the current frame, for which we need to
+// allocate space. In particular, it excludes arguments and results, which are in
+// the callers frame.
+func needAlloc(n *ir.Name) bool {
+	if n.Op() != ir.ONAME {
+		base.FatalfAt(n.Pos(), "%v has unexpected Op %v", n, n.Op())
+	}
+
+	switch n.Class {
+	case ir.PAUTO:
+		return true
+	case ir.PPARAM:
+		return false
+	case ir.PPARAMOUT:
+		return n.IsOutputParamInRegisters()
+
+	default:
+		base.FatalfAt(n.Pos(), "%v has unexpected Class %v", n, n.Class)
+		return false
+	}
+}
+
+func (s *ssafn) AllocFrame(f *ssa.Func) {
+	s.stksize = 0
+	s.stkptrsize = 0
+	fn := s.curfn
+
+	// Mark the PAUTO's unused.
+	for _, ln := range fn.Dcl {
+		if needAlloc(ln) {
+			ln.SetUsed(false)
+		}
+	}
+
+	for _, l := range f.RegAlloc {
+		if ls, ok := l.(ssa.LocalSlot); ok {
+			ls.N.SetUsed(true)
+		}
+	}
+
+	for _, b := range f.Blocks {
+		for _, v := range b.Values {
+			if n, ok := v.Aux.(*ir.Name); ok {
+				switch n.Class {
+				case ir.PPARAMOUT:
+					if n.IsOutputParamInRegisters() && v.Op == ssa.OpVarDef {
+						// ignore VarDef, look for "real" uses.
+						// TODO: maybe do this for PAUTO as well?
+						continue
+					}
+					fallthrough
+				case ir.PPARAM, ir.PAUTO:
+					n.SetUsed(true)
+				}
+			}
+		}
+	}
+
+	// Use sort.Stable instead of sort.Sort so stack layout (and thus
+	// compiler output) is less sensitive to frontend changes that
+	// introduce or remove unused variables.
+	sort.Stable(byStackVar(fn.Dcl))
+
+	// Reassign stack offsets of the locals that are used.
+	lastHasPtr := false
+	for i, n := range fn.Dcl {
+		if n.Op() != ir.ONAME || n.Class != ir.PAUTO && !(n.Class == ir.PPARAMOUT && n.IsOutputParamInRegisters()) {
+			// i.e., stack assign if AUTO, or if PARAMOUT in registers (which has no predefined spill locations)
+			continue
+		}
+		if !n.Used() {
+			fn.Dcl = fn.Dcl[:i]
+			break
+		}
+
+		types.CalcSize(n.Type())
+		w := n.Type().Size()
+		if w >= types.MaxWidth || w < 0 {
+			base.Fatalf("bad width")
+		}
+		if w == 0 && lastHasPtr {
+			// Pad between a pointer-containing object and a zero-sized object.
+			// This prevents a pointer to the zero-sized object from being interpreted
+			// as a pointer to the pointer-containing object (and causing it
+			// to be scanned when it shouldn't be). See issue 24993.
+			w = 1
+		}
+		s.stksize += w
+		s.stksize = types.Rnd(s.stksize, n.Type().Alignment())
+		if n.Type().HasPointers() {
+			s.stkptrsize = s.stksize
+			lastHasPtr = true
+		} else {
+			lastHasPtr = false
+		}
+		n.SetFrameOffset(-s.stksize)
+	}
+
+	s.stksize = types.Rnd(s.stksize, int64(types.RegSize))
+	s.stkptrsize = types.Rnd(s.stkptrsize, int64(types.RegSize))
+}
+
+const maxStackSize = 1 << 30
+
+// Compile builds an SSA backend function,
+// uses it to generate a plist,
+// and flushes that plist to machine code.
+// worker indicates which of the backend workers is doing the processing.
+func Compile(fn *ir.Func, worker int) {
+	f := buildssa(fn, worker)
+	// Note: check arg size to fix issue 25507.
+	if f.Frontend().(*ssafn).stksize >= maxStackSize || f.OwnAux.ArgWidth() >= maxStackSize {
+		largeStackFramesMu.Lock()
+		largeStackFrames = append(largeStackFrames, largeStack{locals: f.Frontend().(*ssafn).stksize, args: f.OwnAux.ArgWidth(), pos: fn.Pos()})
+		largeStackFramesMu.Unlock()
+		return
+	}
+	pp := objw.NewProgs(fn, worker)
+	defer pp.Free()
+	genssa(f, pp)
+	// Check frame size again.
+	// The check above included only the space needed for local variables.
+	// After genssa, the space needed includes local variables and the callee arg region.
+	// We must do this check prior to calling pp.Flush.
+	// If there are any oversized stack frames,
+	// the assembler may emit inscrutable complaints about invalid instructions.
+	if pp.Text.To.Offset >= maxStackSize {
+		largeStackFramesMu.Lock()
+		locals := f.Frontend().(*ssafn).stksize
+		largeStackFrames = append(largeStackFrames, largeStack{locals: locals, args: f.OwnAux.ArgWidth(), callee: pp.Text.To.Offset - locals, pos: fn.Pos()})
+		largeStackFramesMu.Unlock()
+		return
+	}
+
+	pp.Flush() // assemble, fill in boilerplate, etc.
+	// fieldtrack must be called after pp.Flush. See issue 20014.
+	fieldtrack(pp.Text.From.Sym, fn.FieldTrack)
+}
+
+func init() {
+	if race.Enabled {
+		rand.Seed(time.Now().UnixNano())
+	}
+}
+
+// StackOffset returns the stack location of a LocalSlot relative to the
+// stack pointer, suitable for use in a DWARF location entry. This has nothing
+// to do with its offset in the user variable.
+func StackOffset(slot ssa.LocalSlot) int32 {
+	n := slot.N
+	var off int64
+	switch n.Class {
+	case ir.PPARAM, ir.PPARAMOUT:
+		if !n.IsOutputParamInRegisters() {
+			off = n.FrameOffset() + base.Ctxt.FixedFrameSize()
+			break
+		}
+		fallthrough // PPARAMOUT in registers allocates like an AUTO
+	case ir.PAUTO:
+		off = n.FrameOffset()
+		if base.Ctxt.FixedFrameSize() == 0 {
+			off -= int64(types.PtrSize)
+		}
+		if buildcfg.FramePointerEnabled {
+			off -= int64(types.PtrSize)
+		}
+	}
+	return int32(off + slot.Off)
+}
+
+// fieldtrack adds R_USEFIELD relocations to fnsym to record any
+// struct fields that it used.
+func fieldtrack(fnsym *obj.LSym, tracked map[*obj.LSym]struct{}) {
+	if fnsym == nil {
+		return
+	}
+	if !buildcfg.Experiment.FieldTrack || len(tracked) == 0 {
+		return
+	}
+
+	trackSyms := make([]*obj.LSym, 0, len(tracked))
+	for sym := range tracked {
+		trackSyms = append(trackSyms, sym)
+	}
+	sort.Slice(trackSyms, func(i, j int) bool { return trackSyms[i].Name < trackSyms[j].Name })
+	for _, sym := range trackSyms {
+		r := obj.Addrel(fnsym)
+		r.Sym = sym
+		r.Type = objabi.R_USEFIELD
+	}
+}
+
+// largeStack is info about a function whose stack frame is too large (rare).
+type largeStack struct {
+	locals int64
+	args   int64
+	callee int64
+	pos    src.XPos
+}
+
+var (
+	largeStackFramesMu sync.Mutex // protects largeStackFrames
+	largeStackFrames   []largeStack
+)
+
+func CheckLargeStacks() {
+	// Check whether any of the functions we have compiled have gigantic stack frames.
+	sort.Slice(largeStackFrames, func(i, j int) bool {
+		return largeStackFrames[i].pos.Before(largeStackFrames[j].pos)
+	})
+	for _, large := range largeStackFrames {
+		if large.callee != 0 {
+			base.ErrorfAt(large.pos, "stack frame too large (>1GB): %d MB locals + %d MB args + %d MB callee", large.locals>>20, large.args>>20, large.callee>>20)
+		} else {
+			base.ErrorfAt(large.pos, "stack frame too large (>1GB): %d MB locals + %d MB args", large.locals>>20, large.args>>20)
+		}
+	}
+}