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cmd/compile: prove pass misses bounds checks across 32/64-bit integer conversions #81390
Description
When indexing a slice with a 32-bit integer after checking against uint32(len(s)) or int32(len(s)), the prove pass fails to eliminate the bounds check on 64-bit architectures:
func f(s []byte, x uint32, y int32) byte {
if uint32(len(s)) > x {
_ = s[x] // bounds check not eliminated
}
if y >= 0 && int32(len(s)) > y {
return s[y] // bounds check not eliminated
}
return 0
}
Because addValueFact does not record relational facts for OpTrunc*, OpZeroExt*, or OpSignExt* in the poset, inequalities established on narrow integers are lost when zero- or sign-extended back to 64-bit for slice indexing.
Recording these relations in addValueFact eliminates 41 bounds checks across std (primarily in debug/elf, debug/macho, debug/pe, and encoding/binary).
Activity
gabyhelp commentedon Sep 8, 2026
Related Issues
Related Code Changes
(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)
gopherbot commentedon Sep 8, 2026
Change https://go.dev/cl/829264 mentions this issue:
cmd/compile: record poset relations for integer conversions in prove passJunyangShao commentedon Sep 11, 2026
@golang/compiler
gopherbot commentedon Sep 25, 2026
Change https://go.dev/cl/838825 mentions this issue:
cmd/compile: propagate bitwise AND limits and slice/div/mod poset relationsgopherbot commentedon Sep 25, 2026
Change https://go.dev/cl/838826 mentions this issue:
cmd/compile: prove subslice bounds for constant-delta and negative-offset additions