[llvm] AMDGPU: Handle new atomicrmw metadata for fadd case (PR #96760)

[Pierre van Houtryve via llvm-commits]

================
@@ -16062,26 +16062,21 @@ bool SITargetLowering::isKnownNeverNaNForTargetNode(SDValue Op,
                                                             SNaN, Depth);
 }
 
-#if 0
-// FIXME: This should be checked before unsafe fp atomics are enabled
-// Global FP atomic instructions have a hardcoded FP mode and do not support
-// FP32 denormals, and only support v2f16 denormals.
-static bool fpModeMatchesGlobalFPAtomicMode(const AtomicRMWInst *RMW) {
+// On older subtargets, global FP atomic instructions have a hardcoded FP mode
+// and do not support FP32 denormals, and only support v2f16/f64 denormals.
+static bool atomicIgnoresDenormalModeOrFPModeIsFTZ(const AtomicRMWInst *RMW) {
+  if (RMW->hasMetadata("amdgpu.ignore.denormal.mode"))
+    return true;
+
   const fltSemantics &Flt = RMW->getType()->getScalarType()->getFltSemantics();
-  auto DenormMode = RMW->getParent()->getParent()->getDenormalMode(Flt);
-  if (&Flt == &APFloat::IEEEsingle())
-    return DenormMode == DenormalMode::getPreserveSign();
-  return DenormMode == DenormalMode::getIEEE();
-}
-#endif
+  auto DenormMode = RMW->getFunction()->getDenormalMode(Flt);
+  if (DenormMode == DenormalMode::getPreserveSign())
+    return true;
 
-// The amdgpu-unsafe-fp-atomics attribute enables generation of unsafe
-// floating point atomic instructions. May generate more efficient code,
-// but may not respect rounding and denormal modes, and may give incorrect
-// results for certain memory destinations.
-bool unsafeFPAtomicsDisabled(Function *F) {
-  return F->getFnAttribute("amdgpu-unsafe-fp-atomics").getValueAsString() !=
-         "true";
+  // TODO: Remove this.
----------------
Pierre-vh wrote:

Can you elaborate (in a comment) on why/when this should be removed?

https://github.com/llvm/llvm-project/pull/96760