[llvm] [SDAG][NVPTX] Add TLI check for preferring custom FP_TO_SINT operations to FP_TO_UINT (PR #132470)

[Kevin McAfee via llvm-commits]

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@@ -6179,6 +6179,33 @@ Instruction *NVPTXTargetLowering::emitTrailingFence(IRBuilderBase &Builder,
   return nullptr;
 }
 
+// Rather than default to SINT when both UINT and SINT are custom, we only
+// change the opcode when UINT is not legal and SINT is. UINT is preferred when
+// both are custom since unsigned CVT instructions can lead to slightly better
+// SASS code with fewer instructions.
+unsigned NVPTXTargetLowering::getFPToXIntOpcode(unsigned Op, EVT FromVT,
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kalxr wrote:

Note - This seems like it will always return `Op` since I'm unaware of cases in NVPTX where a UINT conversion would be illegal and a SINT conversion would be legal, but wasn't quite sure.

https://github.com/llvm/llvm-project/pull/132470