[PATCH] D55735: [InstSimplify] Simplify saturating add/sub + icmp
Sanjay Patel via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 17 06:36:46 PST 2018
spatel added inline comments.
================
Comment at: lib/Analysis/InstructionSimplify.cpp:2681-2682
+ } else if (match(II.getOperand(1), m_APInt(C))) {
+ if (C->isNegative()) {
+ // ssub.sat(x, -C) produces [SINT_MIN - (-C), SINT_MAX]:
+ Lower = APInt::getSignedMinValue(Width) - *C;
----------------
What happens if C is the signed min value here?
```
define i1 @ssub_icmp_op1_is_min_val(i8 %a) {
%b = call i8 @llvm.ssub.sat.i8(i8 %a, i8 -128)
%c = icmp sle i8 %b, -118
ret i1 %c
}
```
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D55735/new/
https://reviews.llvm.org/D55735
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