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cmd/compile: rewrite cmov(x, x, cond) into x

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I don't think branchelim will intentionally generate theses.
But at the time where branchelim is generating them they might different,
and through opt process they become the same value.

Change-Id: I4a19f1db14c08057b7e782a098f4c18ca36ab7fe
Reviewed-on: https://go-review.googlesource.com/c/go/+/690519
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Mark Freeman <mark@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Jorropo 2025-07-26 03:36:15 +02:00 • committed by Gopher Robot
parent 10c5cf68d4
commit 94645d2413
2 changed files with 11 additions and 0 deletions
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1
src/cmd/compile/internal/ssa/_gen/generic.rules
View file

@ -297,6 +297,7 @@
(CondSelect x _ (ConstBool [true ])) => x
(CondSelect _ y (ConstBool [false])) => y
(CondSelect x x _) => x
// signed integer range: ( c <= x && x (<|<=) d ) -> ( unsigned(x-c) (<|<=) unsigned(d-c) )
(AndB (Leq64 (Const64 [c]) x) ((Less|Leq)64 x (Const64 [d]))) && d >= c => ((Less|Leq)64U (Sub64 <x.Type> x (Const64 <x.Type> [c])) (Const64 <x.Type> [d-c]))

10
src/cmd/compile/internal/ssa/rewritegeneric.go
View file

@ -5722,6 +5722,16 @@ func rewriteValuegeneric_OpCondSelect(v *Value) bool {
v.copyOf(y)
return true
}
// match: (CondSelect x x _)
// result: x
for {
x := v_0
if x != v_1 {
break
}
v.copyOf(x)
return true
}
// match: (CondSelect (Add8 <t> x (Const8 [1])) x bool)
// cond: config.arch != "arm64"
// result: (Add8 x (CvtBoolToUint8 <t> bool))