[dev.regabi] cmd/compile: move stack objects to liveness

Calculating and emitting stack objects are essentially part of
liveness analysis, so move the code from ssagen to liveness. Allows
unexporting liveness.ShouldTrack.

Passes toolstash -cmp.

Change-Id: I88b5b2e75b8dfb46b8b03a2fa09a9236865cbf3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/284413
Trust: Matthew Dempsky <[email protected]>
Run-TryBot: Matthew Dempsky <[email protected]>
Reviewed-by: Cuong Manh Le <[email protected]>
TryBot-Result: Go Bot <[email protected]>

Author: mdempsky

src/cmd/compile/internal/liveness/plive.go

@@ -17,12 +17,14 @@ package liveness
 import (
 	"crypto/md5"
 	"fmt"
+	"sort"
 	"strings"
 
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/bitvec"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/objw"
+	"cmd/compile/internal/reflectdata"
 	"cmd/compile/internal/ssa"
 	"cmd/compile/internal/typebits"
 	"cmd/compile/internal/types"
@@ -174,13 +176,13 @@ type progeffectscache struct {
 	initialized bool
 }
 
-// ShouldTrack reports whether the liveness analysis
+// shouldTrack reports whether the liveness analysis
 // should track the variable n.
 // We don't care about variables that have no pointers,
 // nor do we care about non-local variables,
 // nor do we care about empty structs (handled by the pointer check),
 // nor do we care about the fake PAUTOHEAP variables.
-func ShouldTrack(n *ir.Name) bool {
+func shouldTrack(n *ir.Name) bool {
 	return (n.Class == ir.PAUTO && n.Esc() != ir.EscHeap || n.Class == ir.PPARAM || n.Class == ir.PPARAMOUT) && n.Type().HasPointers()
 }
 
@@ -189,7 +191,7 @@ func ShouldTrack(n *ir.Name) bool {
 func getvariables(fn *ir.Func) ([]*ir.Name, map[*ir.Name]int32) {
 	var vars []*ir.Name
 	for _, n := range fn.Dcl {
-		if ShouldTrack(n) {
+		if shouldTrack(n) {
 			vars = append(vars, n)
 		}
 	}
@@ -1179,9 +1181,54 @@ func Compute(curfn *ir.Func, f *ssa.Func, stkptrsize int64, pp *objw.Progs) Map
 	p.To.Name = obj.NAME_EXTERN
 	p.To.Sym = fninfo.GCLocals
 
+	if x := lv.emitStackObjects(); x != nil {
+		p := pp.Prog(obj.AFUNCDATA)
+		p.From.SetConst(objabi.FUNCDATA_StackObjects)
+		p.To.Type = obj.TYPE_MEM
+		p.To.Name = obj.NAME_EXTERN
+		p.To.Sym = x
+	}
+
 	return lv.livenessMap
 }
 
+func (lv *liveness) emitStackObjects() *obj.LSym {
+	var vars []*ir.Name
+	for _, n := range lv.fn.Dcl {
+		if shouldTrack(n) && n.Addrtaken() && n.Esc() != ir.EscHeap {
+			vars = append(vars, n)
+		}
+	}
+	if len(vars) == 0 {
+		return nil
+	}
+
+	// Sort variables from lowest to highest address.
+	sort.Slice(vars, func(i, j int) bool { return vars[i].FrameOffset() < vars[j].FrameOffset() })
+
+	// Populate the stack object data.
+	// Format must match runtime/stack.go:stackObjectRecord.
+	x := base.Ctxt.Lookup(lv.fn.LSym.Name + ".stkobj")
+	lv.fn.LSym.Func().StackObjects = x
+	off := 0
+	off = objw.Uintptr(x, off, uint64(len(vars)))
+	for _, v := range vars {
+		// Note: arguments and return values have non-negative Xoffset,
+		// in which case the offset is relative to argp.
+		// Locals have a negative Xoffset, in which case the offset is relative to varp.
+		off = objw.Uintptr(x, off, uint64(v.FrameOffset()))
+		off = objw.SymPtr(x, off, reflectdata.TypeLinksym(v.Type()), 0)
+	}
+
+	if base.Flag.Live != 0 {
+		for _, v := range vars {
+			base.WarnfAt(v.Pos(), "stack object %v %v", v, v.Type())
+		}
+	}
+
+	return x
+}
+
 // isfat reports whether a variable of type t needs multiple assignments to initialize.
 // For example:
 //

src/cmd/compile/internal/ssagen/ssa.go

@@ -6467,63 +6467,13 @@ func (s *State) DebugFriendlySetPosFrom(v *ssa.Value) {
 	}
 }
 
-// byXoffset implements sort.Interface for []*ir.Name using Xoffset as the ordering.
-type byXoffset []*ir.Name
-
-func (s byXoffset) Len() int           { return len(s) }
-func (s byXoffset) Less(i, j int) bool { return s[i].FrameOffset() < s[j].FrameOffset() }
-func (s byXoffset) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
-
-func emitStackObjects(e *ssafn, pp *objw.Progs) {
-	var vars []*ir.Name
-	for _, n := range e.curfn.Dcl {
-		if liveness.ShouldTrack(n) && n.Addrtaken() && n.Esc() != ir.EscHeap {
-			vars = append(vars, n)
-		}
-	}
-	if len(vars) == 0 {
-		return
-	}
-
-	// Sort variables from lowest to highest address.
-	sort.Sort(byXoffset(vars))
-
-	// Populate the stack object data.
-	// Format must match runtime/stack.go:stackObjectRecord.
-	x := base.Ctxt.Lookup(e.curfn.LSym.Name + ".stkobj")
-	e.curfn.LSym.Func().StackObjects = x
-	off := 0
-	off = objw.Uintptr(x, off, uint64(len(vars)))
-	for _, v := range vars {
-		// Note: arguments and return values have non-negative Xoffset,
-		// in which case the offset is relative to argp.
-		// Locals have a negative Xoffset, in which case the offset is relative to varp.
-		off = objw.Uintptr(x, off, uint64(v.FrameOffset()))
-		off = objw.SymPtr(x, off, reflectdata.TypeLinksym(v.Type()), 0)
-	}
-
-	// Emit a funcdata pointing at the stack object data.
-	p := pp.Prog(obj.AFUNCDATA)
-	p.From.SetConst(objabi.FUNCDATA_StackObjects)
-	p.To.Type = obj.TYPE_MEM
-	p.To.Name = obj.NAME_EXTERN
-	p.To.Sym = x
-
-	if base.Flag.Live != 0 {
-		for _, v := range vars {
-			base.WarnfAt(v.Pos(), "stack object %v %s", v, v.Type().String())
-		}
-	}
-}
-
 // genssa appends entries to pp for each instruction in f.
 func genssa(f *ssa.Func, pp *objw.Progs) {
 	var s State
 
 	e := f.Frontend().(*ssafn)
 
 	s.livenessMap = liveness.Compute(e.curfn, f, e.stkptrsize, pp)
-	emitStackObjects(e, pp)
 
 	openDeferInfo := e.curfn.LSym.Func().OpenCodedDeferInfo
 	if openDeferInfo != nil {