[llvm] [LangRef] Clarify the semantics of fast-math flags (PR #89442)
Matt Arsenault via llvm-commits
llvm-commits at lists.llvm.org
Tue Apr 23 04:47:13 PDT 2024
================
@@ -3656,6 +3656,45 @@ floating-point transformations.
``fast``
This flag implies all of the others.
+When performing a transformation that involves more that one instruction, the
+flags required to enable the transformation must be set on all instructions
+involved in the transformation, and any new instructions created by the
+transformation should have only those flags set which were set on all the
+original instructions that are being transformed.
----------------
arsenm wrote:
If you want to add more of a guideline, maybe could say something about how you can infer that. e.g. since nnan/ninf imply something about the inputs in one instruction, it implies something about the value in the other use
https://github.com/llvm/llvm-project/pull/89442
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