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cmd/compile: compute OR's maximum limits from argument's limits

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Change-Id: I6902c405cab7bd573f6a721a6ca7c783713ea39a
Reviewed-on: https://go-review.googlesource.com/c/go/+/604456
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Jorropo 2024-08-09 16:35:46 +02:00 • committed by Keith Randall
parent 49621cc311
commit 57df33814a
2 changed files with 22 additions and 2 deletions
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6
src/cmd/compile/internal/ssa/prove.go
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@ -1698,10 +1698,12 @@ func (ft *factsTable) flowLimit(v *Value) bool {
b := ft.limits[v.Args[1].ID]
return ft.unsignedMax(v, minU(a.umax, b.umax))
case OpOr64, OpOr32, OpOr16, OpOr8:
// OR can only make the value bigger.
// OR can only make the value bigger and can't flip bits proved to be zero in both inputs.
a := ft.limits[v.Args[0].ID]
b := ft.limits[v.Args[1].ID]
return ft.unsignedMin(v, maxU(a.umin, b.umin))
return ft.unsignedMinMax(v,
maxU(a.umin, b.umin),
1<<bits.Len64(a.umax|b.umax)-1)
case OpXor64, OpXor32, OpXor16, OpXor8:
// XOR can't flip bits that are proved to be zero in both inputs.
a := ft.limits[v.Args[0].ID]