[PATCH] D102367: [LowerConstantIntrinsics] only accept ConstantData other than UndefValue as constant

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers added a comment.

In D102367#2755587 <https://reviews.llvm.org/D102367#2755587>, @nikic wrote:

> Can you explain why UndefValue needs to be excluded? It's not mentioned in the summary, and the test case does not cover it.

Looks like we disagree with GCC on:

  int foo(void) {
      int i;
      return __builtin_constant_p(i);
  }

Oh, that doesn't produce `undef`...hmm.  @rsmith suggested it in https://bugs.llvm.org/show_bug.cgi?id=41459#c5. I'm happy to add a test for it, but I'm not sure precisely why @rsmith made that recommendation.


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