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cmd/compile: use the shorter version of XOR for breaking POPCNT register 

dependency

XORL accomplishes the same thing while being shorter to encode.

Change-Id: I4397999ff617edb61a7fb7d1eca757a202ab8134
Reviewed-on: https://go-review.googlesource.com/c/go/+/354832
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Josh Bleecher Snyder <josharian@gmail.com>
This commit is contained in:
Jake Ciolek 2021-10-09 20:09:21 +02:00 committed by Josh Bleecher Snyder
parent ba2c9fef03
commit b99abf3cce
1 changed files with 1 additions and 1 deletions
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2
src/cmd/compile/internal/amd64/ssa.go
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@ -1125,7 +1125,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
if v.Args[0].Reg() != v.Reg() {
// POPCNT on Intel has a false dependency on the destination register.
// Xor register with itself to break the dependency.
p := s.Prog(x86.AXORQ)
p := s.Prog(x86.AXORL)
p.From.Type = obj.TYPE_REG
p.From.Reg = v.Reg()
p.To.Type = obj.TYPE_REG