[llvm] [NVPTX] Constant fold NVVM fmin and fmax (PR #121966)

[Lewis Crawford via llvm-commits]

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@@ -1689,6 +1689,28 @@ bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
   case Intrinsic::x86_avx512_cvttsd2usi64:
     return !Call->isStrictFP();
 
+  // NVVM FMax intrinsics
+  case Intrinsic::nvvm_fmax_d:
+  case Intrinsic::nvvm_fmax_f:
+  case Intrinsic::nvvm_fmax_ftz_f:
+  case Intrinsic::nvvm_fmax_ftz_nan_f:
+  case Intrinsic::nvvm_fmax_ftz_nan_xorsign_abs_f:
+  case Intrinsic::nvvm_fmax_ftz_xorsign_abs_f:
+  case Intrinsic::nvvm_fmax_nan_f:
+  case Intrinsic::nvvm_fmax_nan_xorsign_abs_f:
+  case Intrinsic::nvvm_fmax_xorsign_abs_f:
+
+  // NVVM FMin intrinsics
+  case Intrinsic::nvvm_fmin_d:
+  case Intrinsic::nvvm_fmin_f:
+  case Intrinsic::nvvm_fmin_ftz_f:
+  case Intrinsic::nvvm_fmin_ftz_nan_f:
+  case Intrinsic::nvvm_fmin_ftz_nan_xorsign_abs_f:
+  case Intrinsic::nvvm_fmin_ftz_xorsign_abs_f:
+  case Intrinsic::nvvm_fmin_nan_f:
+  case Intrinsic::nvvm_fmin_nan_xorsign_abs_f:
+  case Intrinsic::nvvm_fmin_xorsign_abs_f:
----------------
LewisCrawford wrote:

I'd prefer to just always allow these to be folded, rather than rely on the `isStrictFP()` flag, because as you say, the FP environment should be effectively fixed. The semantics of `llvm.minimum` and `nvvm_fmin` are slightly different too, so they already cannot be used interchangably between host and device, so having slightly different constant-folding behavior for both would make sense.

https://github.com/llvm/llvm-project/pull/121966