[llvm] AMDGPU: Add supports-wgp subtarget feature (PR #212704)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/212704

Whether the hardware supports WGP (work-group processor) execution mode is a
fixed per-GPU capability, distinct from the per-kernel cumode selection. Add
a dedicated feature instead of inferring from the generation and instructions.

Co-authored-by: Claude (Claude-Opus-4.8)

>From 98d4a86154979ed956a5cd114bfc2dca31dcb898 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Wed, 29 Jul 2026 09:53:26 +0200
Subject: [PATCH] AMDGPU: Add supports-wgp subtarget feature

Whether the hardware supports WGP (work-group processor) execution mode is a
fixed per-GPU capability, distinct from the per-kernel cumode selection. Add
a dedicated feature instead of inferring from the generation and instructions.

Co-authored-by: Claude (Claude-Opus-4.8)
---
 llvm/lib/Target/AMDGPU/AMDGPU.td         |  8 ++++----
 llvm/lib/Target/AMDGPU/AMDGPUFeatures.td | 10 ++++++++++
 llvm/lib/Target/AMDGPU/GCNSubtarget.h    |  6 ------
 3 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/AMDGPU.td b/llvm/lib/Target/AMDGPU/AMDGPU.td
index fbfd0e2f6937f..bd639659c2f57 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPU.td
+++ b/llvm/lib/Target/AMDGPU/AMDGPU.td
@@ -1578,7 +1578,7 @@ def FeatureGFX9 : GCNSubtargetFeatureGeneration<"GFX9",
 def FeatureGFX10 : GCNSubtargetFeatureGeneration<"GFX10",
   "gfx10",
   [FeatureFP64, FeatureAddressableLocalMemorySize65536, FeatureMIMG_R128,
-   FeatureSupportsWave32, FeatureSupportsWave64,
+   FeatureSupportsWave32, FeatureSupportsWave64, FeatureSupportsWGP,
    FeatureFlatAddressSpace,
    FeatureCIInsts, Feature16BitInsts,
    FeatureSMemRealTime, FeatureInv2PiInlineImm,
@@ -1609,7 +1609,7 @@ def FeatureGFX10 : GCNSubtargetFeatureGeneration<"GFX10",
 def FeatureGFX11 : GCNSubtargetFeatureGeneration<"GFX11",
   "gfx11",
   [FeatureFP64, FeatureAddressableLocalMemorySize65536, FeatureMIMG_R128,
-   FeatureSupportsWave32, FeatureSupportsWave64,
+   FeatureSupportsWave32, FeatureSupportsWave64, FeatureSupportsWGP,
    FeatureFlatAddressSpace, Feature16BitInsts,
    FeatureInv2PiInlineImm, FeatureApertureRegs,
    FeatureCIInsts, FeatureGFX8Insts, FeatureGFX9Insts, FeatureGFX10Insts,
@@ -1666,7 +1666,7 @@ def FeatureGFX12 : GCNSubtargetFeatureGeneration<"GFX12",
 def FeatureGFX13 : GCNSubtargetFeatureGeneration<"GFX13",
   "gfx13",
   [FeatureFP64, FeatureMIMG_R128,
-   FeatureSupportsWave32, FeatureSupportsWave64,
+   FeatureSupportsWave32, FeatureSupportsWave64, FeatureSupportsWGP,
    FeatureFlatAddressSpace, Feature16BitInsts,
    FeatureInv2PiInlineImm, FeatureApertureRegs,
    FeatureCIInsts, FeatureGFX8Insts, FeatureGFX9Insts, FeatureGFX10Insts,
@@ -2137,7 +2137,7 @@ def FeatureISAVersion11_7_Generic: FeatureSet<
 
 def FeatureISAVersion12 : FeatureSet<
   [FeatureGFX12,
-   FeatureSupportsWave64,
+   FeatureSupportsWave64, FeatureSupportsWGP,
    FeatureBackOffBarrier,
    FeatureAddressableLocalMemorySize65536,
    FeatureLDSBankCount32,
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUFeatures.td b/llvm/lib/Target/AMDGPU/AMDGPUFeatures.td
index b1c09a89433ab..620954d1c984c 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUFeatures.td
+++ b/llvm/lib/Target/AMDGPU/AMDGPUFeatures.td
@@ -60,6 +60,16 @@ def FeatureSupportsWave64 : SubtargetFeature<"supports-wave64",
   [], InlineIgnore
 >;
 
+// Whether the hardware supports WGP (work-group processor) execution
+// mode, as opposed to the per-kernel CU-mode selection
+// (FeatureCuMode).
+def FeatureSupportsWGP : SubtargetFeature<"supports-wgp",
+  "SupportsWGP",
+  "true",
+  "Hardware supports WGP mode",
+  [], InlineIgnore
+>;
+
 class SubtargetFeatureWavefrontSize <int ValueLog2> : SubtargetFeature<
   "wavefrontsize"#!shl(1, ValueLog2),
   "WavefrontSizeLog2",
diff --git a/llvm/lib/Target/AMDGPU/GCNSubtarget.h b/llvm/lib/Target/AMDGPU/GCNSubtarget.h
index c7937d8d33ed5..78ffad6875057 100644
--- a/llvm/lib/Target/AMDGPU/GCNSubtarget.h
+++ b/llvm/lib/Target/AMDGPU/GCNSubtarget.h
@@ -218,12 +218,6 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
   /// the original value.
   bool zeroesHigh16BitsOfDest(unsigned Opcode) const;
 
-  bool supportsWGP() const {
-    if (HasGFX1250Insts)
-      return false;
-    return getGeneration() >= GFX10;
-  }
-
   bool hasHWFP64() const { return HasFP64; }
 
   bool hasAddr64() const {