[llvm] [IR] Add new function attribute nocreateundeforpoison (PR #164809)

[Nikita Popov via llvm-commits]

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@@ -449,7 +449,7 @@ def int_amdgcn_log_clamp : DefaultAttrsIntrinsic<
 
 def int_amdgcn_fmul_legacy : ClangBuiltin<"__builtin_amdgcn_fmul_legacy">,
   DefaultAttrsIntrinsic<[llvm_float_ty], [llvm_float_ty, llvm_float_ty],
-  [IntrNoMem, IntrSpeculatable, Commutative]
+  [IntrNoMem, IntrSpeculatable, Commutative, IntrNoCreateUndefOrPoison]
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nikic wrote:

Instead of adding this to a new intrinsic, can we migrate the existing intrinsics (that don't need special handling) to use the attribute instead of being hardcoded in ValueTracking?

https://github.com/llvm/llvm-project/pull/164809