[llvm-branch-commits] [llvm] AMDGPU: Add subtarget feature for global atomic fadd denormal support (PR #96443)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Matt Arsenault (arsenm)

<details>
<summary>Changes</summary>

Not sure what the behavior for gfx90a is. The SPG says it always flushes.
The instruction documentation says it does not.

---
Full diff: https://github.com/llvm/llvm-project/pull/96443.diff


2 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/AMDGPU.td (+11-2) 
- (modified) llvm/lib/Target/AMDGPU/GCNSubtarget.h (+7) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/AMDGPU.td b/llvm/lib/Target/AMDGPU/AMDGPU.td
index 7ff861f5b144d..5f798b4391704 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPU.td
+++ b/llvm/lib/Target/AMDGPU/AMDGPU.td
@@ -788,6 +788,13 @@ def FeatureFlatAtomicFaddF32Inst
   "Has flat_atomic_add_f32 instruction"
 >;
 
+def FeatureMemoryAtomicFaddF32DenormalSupport
+  : SubtargetFeature<"memory-atomic-fadd-f32-denormal-support",
+  "HasAtomicMemoryAtomicFaddF32DenormalSupport",
+  "true",
+  "global/flat/buffer atomic fadd for float supports denormal handling"
+>;
+
 def FeatureAgentScopeFineGrainedRemoteMemoryAtomics
   : SubtargetFeature<"agent-scope-fine-grained-remote-memory-atomics",
   "HasAgentScopeFineGrainedRemoteMemoryAtomics",
@@ -1425,7 +1432,8 @@ def FeatureISAVersion9_4_Common : FeatureSet<
    FeatureKernargPreload,
    FeatureAtomicFMinFMaxF64GlobalInsts,
    FeatureAtomicFMinFMaxF64FlatInsts,
-   FeatureAgentScopeFineGrainedRemoteMemoryAtomics
+   FeatureAgentScopeFineGrainedRemoteMemoryAtomics,
+   FeatureMemoryAtomicFaddF32DenormalSupport
    ]>;
 
 def FeatureISAVersion9_4_0 : FeatureSet<
@@ -1628,7 +1636,8 @@ def FeatureISAVersion12 : FeatureSet<
    FeatureVGPRSingleUseHintInsts,
    FeatureScalarDwordx3Loads,
    FeatureDPPSrc1SGPR,
-   FeatureMaxHardClauseLength32]>;
+   FeatureMaxHardClauseLength32,
+   FeatureMemoryAtomicFaddF32DenormalSupport]>;
 
 def FeatureISAVersion12_Generic: FeatureSet<
   !listconcat(FeatureISAVersion12.Features,
diff --git a/llvm/lib/Target/AMDGPU/GCNSubtarget.h b/llvm/lib/Target/AMDGPU/GCNSubtarget.h
index c40efbdcf7f0b..674d84422538f 100644
--- a/llvm/lib/Target/AMDGPU/GCNSubtarget.h
+++ b/llvm/lib/Target/AMDGPU/GCNSubtarget.h
@@ -167,6 +167,7 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
   bool HasAtomicFlatPkAdd16Insts = false;
   bool HasAtomicFaddRtnInsts = false;
   bool HasAtomicFaddNoRtnInsts = false;
+  bool HasAtomicMemoryAtomicFaddF32DenormalSupport = false;
   bool HasAtomicBufferGlobalPkAddF16NoRtnInsts = false;
   bool HasAtomicBufferGlobalPkAddF16Insts = false;
   bool HasAtomicCSubNoRtnInsts = false;
@@ -872,6 +873,12 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
 
   bool hasFlatAtomicFaddF32Inst() const { return HasFlatAtomicFaddF32Inst; }
 
+  /// \return true if the target's flat, global, and buffer atomic fadd for
+  /// float supports denormal handling.
+  bool hasMemoryAtomicFaddF32DenormalSupport() const {
+    return HasAtomicMemoryAtomicFaddF32DenormalSupport;
+  }
+
   /// \return true if atomic operations targeting fine-grained memory work
   /// correctly at device scope, in allocations in host or peer PCIe device
   /// memory.

``````````

</details>


https://github.com/llvm/llvm-project/pull/96443