[PATCH] D62414: [InstCombine] canonicalize fcmp+select to minnum/maxnum intrinsics

Tue Jun 11 07:43:07 PDT 2019

cameron.mcinally added inline comments.

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Comment at: llvm/test/Transforms/InstCombine/fast-math.ll:884
 ; CHECK-LABEL: @min3(
-; CHECK-NEXT:    [[TMP1:%.*]] = fcmp nnan nsz olt double [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = select nnan nsz i1 [[TMP1]], double [[A]], double [[B]]
-; CHECK-NEXT:    ret double [[TMP2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan nsz double @llvm.minnum.f64(double [[A:%.*]], double [[B:%.*]])
+; CHECK-NEXT:    ret double [[TMP1]]
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cameron.mcinally wrote:
> Do we want NSZ here? I see that this was an artifact of the old fcmp+select lowering, but I'm not sure if it is correct. Definitely not IEEE-754 compliant...
Now that I think about it, maybe it would be better to skip the fcmp+sel step and lower the libm call directly into the intrinsic?

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D62414/new/

https://reviews.llvm.org/D62414