AMDGPU: Add target feature for aligned VGPR requirement (#155336)

This now applies to gfx90a+ and gfx1250, so add a dedicated feature
for it so the feature check can be composed correctly with unrelated
properties. Probably would be better to invert this, but that turns
out to be difficult given the current assumptions.

Author: arsenm

llvm/lib/Target/AMDGPU/AMDGPU.td

@@ -419,6 +419,12 @@ def FeatureGFX9Insts : SubtargetFeature<"gfx9-insts",
   "Additional instructions for GFX9+"
 >;
 
+def FeatureRequiresAlignedVGPRs : SubtargetFeature<"vgpr-align2",
+  "RequiresAlignVGPR",
+  "true",
+  "VGPR and AGPR tuple operands require even alignment"
+>;
+
 def FeatureGFX90AInsts : SubtargetFeature<"gfx90a-insts",
   "GFX90AInsts",
   "true",
@@ -1721,6 +1727,7 @@ def FeatureISAVersion9_0_9 : FeatureSet<
 def FeatureISAVersion9_0_A : FeatureSet<
   !listconcat(FeatureISAVersion9_0_MI_Common.Features,
     [FeatureGFX90AInsts,
+     FeatureRequiresAlignedVGPRs,
      FeatureFmacF64Inst,
      FeatureDPALU_DPP,
      FeaturePackedFP32Ops,
@@ -1743,6 +1750,7 @@ def FeatureISAVersion9_4_Common : FeatureSet<
   [FeatureGFX9,
    FeatureGFX90AInsts,
    FeatureGFX940Insts,
+   FeatureRequiresAlignedVGPRs,
    FeatureFmaMixInsts,
    FeatureLDSBankCount32,
    FeatureDLInsts,
@@ -2019,6 +2027,7 @@ def FeatureISAVersion12 : FeatureSet<
 def FeatureISAVersion12_50 : FeatureSet<
   [FeatureGFX12,
    FeatureGFX1250Insts,
+   FeatureRequiresAlignedVGPRs,
    FeatureCUStores,
    FeatureAddressableLocalMemorySize327680,
    FeatureCuMode,

llvm/lib/Target/AMDGPU/GCNSubtarget.h

@@ -198,6 +198,7 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
   bool DynamicVGPR = false;
   bool DynamicVGPRBlockSize32 = false;
   bool HasVMemToLDSLoad = false;
+  bool RequiresAlignVGPR = false;
 
   // This should not be used directly. 'TargetID' tracks the dynamic settings
   // for SRAMECC.
@@ -1350,7 +1351,7 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
   }
 
   /// Return if operations acting on VGPR tuples require even alignment.
-  bool needsAlignedVGPRs() const { return GFX90AInsts || GFX1250Insts; }
+  bool needsAlignedVGPRs() const { return RequiresAlignVGPR; }
 
   /// Return true if the target has the S_PACK_HL_B32_B16 instruction.
   bool hasSPackHL() const { return GFX11Insts; }