cmd/compile: issue VarDef only for pointer-ful types

Use OpVarDef only when the variable being defined has pointers in it.
VarDef markers are only used for liveness analysis, and that only
runs on pointer-ful variables.

Fixes #53810

Change-Id: I09b0ef7ed31e72528916fe79325f80bbe69ff9b4
Reviewed-on: https://go-review.googlesource.com/c/go/+/419320
Reviewed-by: David Chase <[email protected]>
Reviewed-by: Joedian Reid <[email protected]>
Run-TryBot: Keith Randall <[email protected]>

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

@@ -5,6 +5,7 @@
 package ssa
 
 import (
+ "cmd/compile/internal/ir"
  "cmd/internal/obj/s390x"
  "math"
  "math/bits"
@@ -312,6 +313,10 @@ func checkFunc(f *Func) {
  if !v.Args[1].Type.IsInteger() {
  f.Fatalf("bad arg 1 type to %s: want integer, have %s", v.Op, v.Args[1].LongString())
  }
+ case OpVarDef:
+ if !v.Aux.(*ir.Name).Type().HasPointers() {
+ f.Fatalf("vardef must have pointer type %s", v.Aux.(*ir.Name).Type().String())
+ }
 
  }
 

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

@@ -22,7 +22,7 @@ func TestCSEAuxPartitionBug(t *testing.T) {
  arg1Aux := &tstAux{"arg1-aux"}
  arg2Aux := &tstAux{"arg2-aux"}
  arg3Aux := &tstAux{"arg3-aux"}
- a := c.Frontend().Auto(src.NoXPos, c.config.Types.Int8)
+ a := c.Frontend().Auto(src.NoXPos, c.config.Types.Int8.PtrTo())
 
  // construct lots of values with args that have aux values and place
  // them in an order that triggers the bug
@@ -93,7 +93,7 @@ func TestCSEAuxPartitionBug(t *testing.T) {
 // TestZCSE tests the zero arg cse.
 func TestZCSE(t *testing.T) {
  c := testConfig(t)
- a := c.Frontend().Auto(src.NoXPos, c.config.Types.Int8)
+ a := c.Frontend().Auto(src.NoXPos, c.config.Types.Int8.PtrTo())
 
  fun := c.Fun("entry",
  Bloc("entry",

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

@@ -72,6 +72,7 @@ func (TestFrontend) StringData(s string) *obj.LSym {
 }
 func (TestFrontend) Auto(pos src.XPos, t *types.Type) *ir.Name {
  n := ir.NewNameAt(pos, &types.Sym{Name: "aFakeAuto"})
+ n.SetType(t)
  n.Class = ir.PAUTO
  return n
 }

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

@@ -630,7 +630,9 @@ func (s *state) zeroResults() {
  if typ := n.Type(); TypeOK(typ) {
  s.assign(n, s.zeroVal(typ), false, 0)
  } else {
- s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, n, s.mem())
+ if typ.HasPointers() {
+ s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, n, s.mem())
+ }
  s.zero(n.Type(), s.decladdrs[n])
  }
  }
@@ -1978,14 +1980,16 @@ func (s *state) exit() *ssa.Block {
  for i, f := range resultFields {
  n := f.Nname.(*ir.Name)
  if s.canSSA(n) { // result is in some SSA variable
- if !n.IsOutputParamInRegisters() {
+ if !n.IsOutputParamInRegisters() && n.Type().HasPointers() {
  // We are about to store to the result slot.
  s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, n, s.mem())
  }
  results[i] = s.variable(n, n.Type())
  } else if !n.OnStack() { // result is actually heap allocated
  // We are about to copy the in-heap result to the result slot.
- s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, n, s.mem())
+ if n.Type().HasPointers() {
+ s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, n, s.mem())
+ }
  ha := s.expr(n.Heapaddr)
  s.instrumentFields(n.Type(), ha, instrumentRead)
  results[i] = s.newValue2(ssa.OpDereference, n.Type(), ha, s.mem())
@@ -3607,7 +3611,7 @@ func (s *state) assign(left ir.Node, right *ssa.Value, deref bool, skip skipMask
 
  // If this assignment clobbers an entire local variable, then emit
  // OpVarDef so liveness analysis knows the variable is redefined.
- if base, ok := clobberBase(left).(*ir.Name); ok && base.OnStack() && skip == 0 {
+ if base, ok := clobberBase(left).(*ir.Name); ok && base.OnStack() && skip == 0 && t.HasPointers() {
  s.vars[memVar] = s.newValue1Apos(ssa.OpVarDef, types.TypeMem, base, s.mem(), !ir.IsAutoTmp(base))
  }
 
@@ -4843,14 +4847,18 @@ func (s *state) openDeferSave(t *types.Type, val *ssa.Value) *ssa.Value {
  // Force the tmp storing this defer function to be declared in the entry
  // block, so that it will be live for the defer exit code (which will
  // actually access it only if the associated defer call has been activated).
- s.defvars[s.f.Entry.ID][memVar] = s.f.Entry.NewValue1A(src.NoXPos, ssa.OpVarDef, types.TypeMem, temp, s.defvars[s.f.Entry.ID][memVar])
+ if t.HasPointers() {
+ s.defvars[s.f.Entry.ID][memVar] = s.f.Entry.NewValue1A(src.NoXPos, ssa.OpVarDef, types.TypeMem, temp, s.defvars[s.f.Entry.ID][memVar])
+ }
  s.defvars[s.f.Entry.ID][memVar] = s.f.Entry.NewValue1A(src.NoXPos, ssa.OpVarLive, types.TypeMem, temp, s.defvars[s.f.Entry.ID][memVar])
  addrTemp = s.f.Entry.NewValue2A(src.NoXPos, ssa.OpLocalAddr, types.NewPtr(temp.Type()), temp, s.sp, s.defvars[s.f.Entry.ID][memVar])
  } else {
  // Special case if we're still in the entry block. We can't use
  // the above code, since s.defvars[s.f.Entry.ID] isn't defined
  // until we end the entry block with s.endBlock().
- s.vars[memVar] = s.newValue1Apos(ssa.OpVarDef, types.TypeMem, temp, s.mem(), false)
+ if t.HasPointers() {
+ s.vars[memVar] = s.newValue1Apos(ssa.OpVarDef, types.TypeMem, temp, s.mem(), false)
+ }
  s.vars[memVar] = s.newValue1Apos(ssa.OpVarLive, types.TypeMem, temp, s.mem(), false)
  addrTemp = s.newValue2Apos(ssa.OpLocalAddr, types.NewPtr(temp.Type()), temp, s.sp, s.mem(), false)
  }
@@ -5032,7 +5040,9 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
  t := deferstruct()
  d := typecheck.TempAt(n.Pos(), s.curfn, t)
 
- s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, d, s.mem())
+ if t.HasPointers() {
+ s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, d, s.mem())
+ }
  addr := s.addr(d)
 
  // Must match deferstruct() below and src/runtime/runtime2.go:_defer.
@@ -6428,7 +6438,9 @@ func (s *state) dottype1(pos src.XPos, src, dst *types.Type, iface, source, targ
 // temp allocates a temp of type t at position pos
 func (s *state) temp(pos src.XPos, t *types.Type) (*ir.Name, *ssa.Value) {
  tmp := typecheck.TempAt(pos, s.curfn, t)
- s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, tmp, s.mem())
+ if t.HasPointers() {
+ s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, tmp, s.mem())
+ }
  addr := s.addr(tmp)
  return tmp, addr
 }