[PATCH] D118426: [InstCombine] Remove side effect of replaced constrained intrinsics

[Serge Pavlov via Phabricator via llvm-commits]

sepavloff marked an inline comment as done.
sepavloff added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp:1057
+  if (CI.use_empty() && isa<ConstrainedFPIntrinsic>(CI))
+    if (SimplifyCall(&CI, SQ.getWithInstruction(&CI)))
+      return &CI;
----------------
andrew.w.kaylor wrote:
> Relying on SimplifyCall() here to determine whether the call has side effects is still more restrictive than necessary. For example, if the exception behavior argument is not fp::ExceptionBehavior::ebStrict and the call has no users, it can be removed even if the arguments are non-constant or the operation would raise an exception.
Actually there is no additional restrictions. `wouldInstructionBeTriviallyDead` already recognizes that a constrained  intrinsic calls with the exception behavior argument other than `ebStrict` may be removed. So if such call result is not used, it is removed in `prepareICWorklistFromFunction` and does not participate in instruction combining. If such call is replaced by `SimplifyCall`, it is removed due to the same reason. The test `f_eval_maytrap` demonstrates this case.


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  https://reviews.llvm.org/D118426/new/

https://reviews.llvm.org/D118426