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cmd/compile: use only bit patterns in isNonNegative

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CL 212777 added a check to isNonNegative
to return true for unsigned values.
However, the SSA backend isn't type safe
enough for that to be sound.
The other checks in isNonNegative
look only at the pattern of bits.
Remove the type-based check.

Updates #37753

Change-Id: I059d0e86353453133f2a160dce53af299f42e533
Reviewed-on: https://go-review.googlesource.com/c/go/+/222620
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Josh Bleecher Snyder 2020-03-09 06:37:49 -07:00
parent 3afa86d632
commit 5fac45a320
2 changed files with 21 additions and 3 deletions
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6
src/cmd/compile/internal/ssa/prove.go
View file

@ -1305,9 +1305,9 @@ func isNonNegative(v *Value) bool {
if !v.Type.IsInteger() {
panic("isNonNegative bad type")
}
if !v.Type.IsSigned() {
return true
}
// TODO: return true if !v.Type.IsSigned()
// SSA isn't type-safe enough to do that now (issue 37753).
// The checks below depend only on the pattern of bits.
switch v.Op {
case OpConst64: