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cmd/compile: compute Trunc's limits from argument's limits

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Change-Id: I419faa781db085b98ea25008ca127d0317fb34e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/605695
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
This commit is contained in:
Jorropo 2024-08-14 21:25:08 +02:00 committed by Keith Randall
parent 68c431e89f
commit 4f2c0e5d08
2 changed files with 25 additions and 0 deletions
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5
src/cmd/compile/internal/ssa/prove.go
View File

@ -1643,6 +1643,11 @@ func (ft *factsTable) flowLimit(v *Value) bool {
case OpSignExt8to64, OpSignExt8to32, OpSignExt8to16, OpSignExt16to64, OpSignExt16to32, OpSignExt32to64: case OpSignExt8to64, OpSignExt8to32, OpSignExt8to16, OpSignExt16to64, OpSignExt16to32, OpSignExt32to64:
a := ft.limits[v.Args[0].ID] a := ft.limits[v.Args[0].ID]
return ft.signedMinMax(v, a.min, a.max) return ft.signedMinMax(v, a.min, a.max)
case OpTrunc64to8, OpTrunc64to16, OpTrunc64to32, OpTrunc32to8, OpTrunc32to16, OpTrunc16to8:
a := ft.limits[v.Args[0].ID]
if a.umax <= 1<<(uint64(v.Type.Size())*8)-1 {
return ft.unsignedMinMax(v, a.umin, a.umax)
}
// math/bits // math/bits
case OpCtz64: case OpCtz64:

20
test/prove.go
View File

@ -1586,6 +1586,26 @@ func div64s(a, b int64, ensureAllBranchesCouldHappen func() bool) int64 {
return z return z
} }
func trunc64to16(a uint64, ensureAllBranchesCouldHappen func() bool) uint16 {
a &= 0xfff
a |= 0xff
z := uint16(a)
if ensureAllBranchesCouldHappen() && z > 0xfff { // ERROR "Disproved Less16U$"
return 42
}
if ensureAllBranchesCouldHappen() && z <= 0xfff { // ERROR "Proved Leq16U$"
return 1337
}
if ensureAllBranchesCouldHappen() && z < 0xff { // ERROR "Disproved Less16U$"
return 42
}
if ensureAllBranchesCouldHappen() && z >= 0xff { // ERROR "Proved Leq16U$"
return 1337
}
return z
}
//go:noinline //go:noinline
func useInt(a int) { func useInt(a int) {
} }