[llvm] [AMDGPU] Fix fmul/fma legacy sign-of-zero miscompile (PR #203567)

[Wooseok Lee via llvm-commits]

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@@ -405,16 +405,22 @@ bool GCNTTIImpl::canSimplifyLegacyMulToMul(const Instruction &I,
   // cases then we can use a normal multiply instead.
   // TODO: Create and use isKnownFiniteNonZero instead of just matching
   // constants here.
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wooseoklee wrote:

Updated code based on this. Let me know if there is anything that needs to be updated.

https://github.com/llvm/llvm-project/pull/203567