AMDGPU: Add subtarget feature for memory atomic fadd f64

Author: arsenm

llvm/lib/Target/AMDGPU/AMDGPU.td

@@ -788,6 +788,13 @@ def FeatureFlatAtomicFaddF32Inst
   "Has flat_atomic_add_f32 instruction"
 >;
 
+def FeatureFlatBufferGlobalAtomicFaddF64Inst
+  : SubtargetFeature<"flat-buffer-global-fadd-f64-inst",
+  "HasFlatBufferGlobalAtomicFaddF64Inst",
+  "true",
+  "Has flat, buffer, and global instructions for f64 atomic fadd"
+>;
+
 def FeatureMemoryAtomicFaddF32DenormalSupport
   : SubtargetFeature<"memory-atomic-fadd-f32-denormal-support",
   "HasAtomicMemoryAtomicFaddF32DenormalSupport",
@@ -1388,7 +1395,8 @@ def FeatureISAVersion9_0_A : FeatureSet<
      FeatureBackOffBarrier,
      FeatureKernargPreload,
      FeatureAtomicFMinFMaxF64GlobalInsts,
-     FeatureAtomicFMinFMaxF64FlatInsts
+     FeatureAtomicFMinFMaxF64FlatInsts,
+     FeatureFlatBufferGlobalAtomicFaddF64Inst
      ])>;
 
 def FeatureISAVersion9_0_C : FeatureSet<

llvm/lib/Target/AMDGPU/GCNSubtarget.h

@@ -174,6 +174,7 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
   bool HasAtomicGlobalPkAddBF16Inst = false;
   bool HasAtomicBufferPkAddBF16Inst = false;
   bool HasFlatAtomicFaddF32Inst = false;
+  bool HasFlatBufferGlobalAtomicFaddF64Inst = false;
   bool HasDefaultComponentZero = false;
   bool HasAgentScopeFineGrainedRemoteMemoryAtomics = false;
   bool HasDefaultComponentBroadcast = false;
@@ -873,6 +874,12 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
 
   bool hasFlatAtomicFaddF32Inst() const { return HasFlatAtomicFaddF32Inst; }
 
+  /// \return true if the target has flat, global, and buffer atomic fadd for
+  /// double.
+  bool hasFlatBufferGlobalAtomicFaddF64Inst() const {
+    return HasFlatBufferGlobalAtomicFaddF64Inst;
+  }
+
   /// \return true if the target's flat, global, and buffer atomic fadd for
   /// float supports denormal handling.
   bool hasMemoryAtomicFaddF32DenormalSupport() const {

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -16028,7 +16028,7 @@ SITargetLowering::shouldExpandAtomicRMWInIR(AtomicRMWInst *RMW) const {
       return AtomicExpansionKind::CmpXChg;
 
     // global and flat atomic fadd f64: gfx90a, gfx940.
-    if (Subtarget->hasGFX90AInsts() && Ty->isDoubleTy())
+    if (Subtarget->hasFlatBufferGlobalAtomicFaddF64Inst() && Ty->isDoubleTy())
       return ReportUnsafeHWInst(AtomicExpansionKind::None);
 
     if (AS != AMDGPUAS::FLAT_ADDRESS && Ty->isFloatTy()) {