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[dev.regabi] cmd/compile: handle OCONVNOP better in ssa

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This CL improves handling of OCONVNOP nodes during ssa generation,
so it is not toolstash safe.

An OCONVNOP wrapper is necessary for the "for" condition of
certain compiled range loops, and the boolean evaluator was
not looking through them properly, generating unnecessary
temporaries. That change saved 8k of the (13 MB) go binary.

The other changes just streamline the handling of OCONVNOP
to be more like what OSTMTEXPR will be like. They have no
effect on output size but do tweak the ssa graph a little, which
causes different register decisions and therefore different output.

Change-Id: I9e1dcd413b60944e21554c3e3f2bdc9adcee7634
Reviewed-on: https://go-review.googlesource.com/c/go/+/274598
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Russ Cox 2020-12-01 12:02:16 -05:00
parent 00e5727790
commit 59b8916d48
2 changed files with 13 additions and 0 deletions
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10
src/cmd/compile/internal/gc/ssa.go
View file

@ -2103,6 +2103,9 @@ func (s *state) expr(n ir.Node) *ssa.Value {
// Assume everything will work out, so set up our return value.
// Anything interesting that happens from here is a fatal.
x := s.expr(n.Left())
if to == from {
return x
}
// Special case for not confusing GC and liveness.
// We don't want pointers accidentally classified
@ -2966,6 +2969,10 @@ func (s *state) condBranch(cond ir.Node, yes, no *ssa.Block, likely int8) {
s.stmtList(cond.Init())
s.condBranch(cond.Left(), no, yes, -likely)
return
case ir.OCONVNOP:
s.stmtList(cond.Init())
s.condBranch(cond.Left(), yes, no, likely)
return
}
c := s.expr(cond)
b := s.endBlock()
@ -4903,6 +4910,9 @@ func (s *state) addr(n ir.Node) *ssa.Value {
return s.newValue1I(ssa.OpOffPtr, t, n.Offset(),
s.entryNewValue0(ssa.OpGetClosurePtr, s.f.Config.Types.BytePtr))
case ir.OCONVNOP:
if n.Type() == n.Left().Type() {
return s.addr(n.Left())
}
addr := s.addr(n.Left())
return s.newValue1(ssa.OpCopy, t, addr) // ensure that addr has the right type
case ir.OCALLFUNC, ir.OCALLINTER, ir.OCALLMETH:

3
src/cmd/compile/internal/gc/walk.go
View file

@ -966,6 +966,9 @@ opswitch:
case ir.OCONV, ir.OCONVNOP:
n.SetLeft(walkexpr(n.Left(), init))
if n.Op() == ir.OCONVNOP && n.Type() == n.Left().Type() {
return n.Left()
}
if n.Op() == ir.OCONVNOP && checkPtr(Curfn, 1) {
if n.Type().IsPtr() && n.Left().Type().IsUnsafePtr() { // unsafe.Pointer to *T
n = walkCheckPtrAlignment(n, init, nil)