[PATCH] D137444: InstCombine: Fold compare with smallest normal if input denormals are flushed

[Matt Arsenault via Phabricator via llvm-commits]

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Try to simplify comparisons with the smallest normalized value. If
denormals will be treated as 0, we can simplify by using an equality
comparison with 0.

      

fcmp olt fabs(x), smallest_normalized_number -> fcmp oeq x, 0.0
fcmp ult fabs(x), smallest_normalized_number -> fcmp ueq x, 0.0
fcmp oge fabs(x), smallest_normalized_number -> fcmp one x, 0.0
fcmp ult fabs(x), smallest_normalized_number -> fcmp ueq x, 0.0

      

The device libraries have a few range checks that look like
this for denormal handling paths.


https://reviews.llvm.org/D137444

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/fcmp-denormals-are-zero.ll

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