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

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Change-Id: Id522bde5bba627d9cdc8c3d8e907bdc168e5b13c
Reviewed-on: https://go-review.googlesource.com/c/go/+/605157
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
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Jorropo 2024-08-13 18:27:38 +02:00 • committed by Keith Randall
parent 194fa2eb6c
commit e23ebec90d
2 changed files with 34 additions and 0 deletions
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11
src/cmd/compile/internal/ssa/prove.go
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@ -1780,6 +1780,17 @@ func (ft *factsTable) flowLimit(v *Value) bool {
b := ft.limits[v.Args[1].ID]
// Underflow in the arithmetic below is ok, it gives to MaxUint64 which does nothing to the limit.
return ft.unsignedMax(v, minU(a.umax, b.umax-1))
case OpDiv64u, OpDiv32u, OpDiv16u, OpDiv8u:
a := ft.limits[v.Args[0].ID]
b := ft.limits[v.Args[1].ID]
lim := noLimit
if b.umax > 0 {
lim = lim.unsignedMin(a.umin / b.umax)
}
if b.umin > 0 {
lim = lim.unsignedMax(a.umax / b.umin)
}
return ft.newLimit(v, lim)
case OpPhi:
// Compute the union of all the input phis.