[PATCH] D143766: [InstCombine][WIP] Fix InstCombinerImpl::foldICmpMulConstant for nsw and nuw mul with unsigned compare.

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:2082
           MulTy, APIntOps::RoundingSDiv(C, *MulC, APInt::Rounding::DOWN));
-  } else {
-    assert(Mul->hasNoUnsignedWrap() && "Expected mul nuw");
+  } else if (Mul->hasNoUnsignedWrap()) {
     if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_UGE)
----------------
Does this need an `ICmpInst::isUnsigned(Pred)` check aswell?


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Comment at: llvm/test/Transforms/InstCombine/icmp-mul.ll:949
 ; CHECK-LABEL: @splat_mul_unknown_lz(
-; CHECK-NEXT:    [[Z:%.*]] = zext i32 [[X:%.*]] to i128
-; CHECK-NEXT:    [[M:%.*]] = mul nuw nsw i128 [[Z]], 18446744078004518913
-; CHECK-NEXT:    [[R:%.*]] = icmp ult i128 [[M]], 39614081257132168796771975168
+; CHECK-NEXT:    [[R:%.*]] = icmp sgt i32 [[X:%.*]], -1
 ; CHECK-NEXT:    ret i1 [[R]]
----------------
imo a few more tests (at least one with unsigned pred).


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D143766/new/

https://reviews.llvm.org/D143766