From f44404ebbfeff57f3e45ebf4b314a320bb89841f Mon Sep 17 00:00:00 2001 From: Matthew Dempsky Date: Tue, 11 Jun 2019 19:52:58 -0700 Subject: cmd/compile: fix range analysis of small signed integers 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 Reviewed-by: Josh Bleecher Snyder Reviewed-by: David Chase Reviewed-by: Keith Randall TryBot-Result: Gobot Gobot --- src/cmd/compile/internal/ssa/prove.go | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) (limited to 'src') diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go index a73cd613f2..7c69327990 100644 --- a/src/cmd/compile/internal/ssa/prove.go +++ b/src/cmd/compile/internal/ssa/prove.go @@ -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 { -- cgit v1.3