Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

cmd/compile: fix range analysis of small signed integers

Browse source 
For int8, int16, and int32, comparing their unsigned value to MaxInt64
to determine non-negativity doesn't make sense, because they have
negative values whose unsigned representation is smaller than that.
Fix is simply to compare with the appropriate upper bound based on the
value type's size.

Fixes #32560.

Change-Id: Ie7afad7a56af92bd890ba5ff33c86d1df06cfd9a
Reviewed-on: https://go-review.googlesource.com/c/go/+/181797
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Matthew Dempsky 2019-06-11 19:52:58 -07:00
parent 87367cf86a
commit f44404ebbf
2 changed files with 67 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

18
src/cmd/compile/internal/ssa/prove.go
View file

@ -553,15 +553,29 @@ func (ft *factsTable) isNonNegative(v *Value) bool {
return true
}
var max int64
switch v.Type.Size() {
case 1:
max = math.MaxInt8
case 2:
max = math.MaxInt16
case 4:
max = math.MaxInt32
case 8:
max = math.MaxInt64
default:
panic("unexpected integer size")
}
// Check if the recorded limits can prove that the value is positive
if l, has := ft.limits[v.ID]; has && (l.min >= 0 || l.umax <= math.MaxInt64) {
if l, has := ft.limits[v.ID]; has && (l.min >= 0 || l.umax <= uint64(max)) {
return true
}
// Check if v = x+delta, and we can use x's limits to prove that it's positive
if x, delta := isConstDelta(v); x != nil {
if l, has := ft.limits[x.ID]; has {
if delta > 0 && l.min >= -delta && l.max <= math.MaxInt64-delta {
if delta > 0 && l.min >= -delta && l.max <= max-delta {
return true
}
if delta < 0 && l.min >= -delta {