Get ArchVGPR alloc granule from AMDGPU::IsaInfo

Author: lucas-rami

llvm/lib/Target/AMDGPU/GCNRegPressure.h

@@ -63,7 +63,8 @@ struct GCNRegPressure {
   /// and \p NumAGPRs AGPRS, for a target with a unified VGPR file.
   inline static unsigned getUnifiedVGPRNum(unsigned NumArchVGPRs,
                                            unsigned NumAGPRs) {
-    return alignTo(NumArchVGPRs, 4) + NumAGPRs;
+    return alignTo(NumArchVGPRs, AMDGPU::IsaInfo::getArchVGPRAllocGranule()) +
+           NumAGPRs;
   }
 
   /// \returns the ArchVGPR32 pressure

llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp

@@ -1714,9 +1714,6 @@ struct ExcessRP {
   /// Whether the subtarget has a unified RF.
   bool UnifiedRF;
 
-  /// ArchVGPR allocation granule for unified RFs with AGPR usage.
-  static const unsigned Granule = 4;
-
   /// Constructs the excess RP model; determines the excess pressure w.r.t. a
   /// maximum number of allowed VGPRs.
   ExcessRP(const GCNSubtarget &ST, const GCNRegPressure &RP, unsigned MaxVGPRs);
@@ -1785,6 +1782,7 @@ ExcessRP::ExcessRP(const GCNSubtarget &ST, const GCNRegPressure &RP,
 
   // Check overall VGPR usage against the limit; any excess above addressable
   // register limits has already been accounted for.
+  const unsigned Granule = AMDGPU::IsaInfo::getArchVGPRAllocGranule();
   unsigned NumVGPRs = GCNRegPressure::getUnifiedVGPRNum(NumArchVGPRs, NumAGPRs);
   if (NumVGPRs > MaxVGPRs) {
     VGPRs = NumVGPRs - MaxVGPRs;
@@ -1812,6 +1810,7 @@ bool ExcessRP::saveArchVGPRs(unsigned NumRegs, bool UseArchVGPRForAGPRSpill) {
     unsigned NumSavedRegs = 0;
 
     // Count the number of whole ArchVGPR allocation granules we can save.
+    const unsigned Granule = AMDGPU::IsaInfo::getArchVGPRAllocGranule();
     if (unsigned NumGranules = NumRegs / Granule; NumGranules) {
       NumSavedRegs = NumGranules * Granule;
       NumRegs -= NumSavedRegs;

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp

@@ -1194,6 +1194,8 @@ unsigned getVGPREncodingGranule(const MCSubtargetInfo *STI,
   return IsWave32 ? 8 : 4;
 }
 
+unsigned getArchVGPRAllocGranule() { return 4; }
+
 unsigned getTotalNumVGPRs(const MCSubtargetInfo *STI) {
   if (STI->getFeatureBits().test(FeatureGFX90AInsts))
     return 512;

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.h

@@ -318,6 +318,10 @@ unsigned getVGPREncodingGranule(
     const MCSubtargetInfo *STI,
     std::optional<bool> EnableWavefrontSize32 = std::nullopt);
 
+/// For subtargets with a unified VGPR file and mixed ArchVGPR/AGPR usage,
+/// returns the allocation granule for ArchVGPRs.
+unsigned getArchVGPRAllocGranule();
+
 /// \returns Total number of VGPRs for given subtarget \p STI.
 unsigned getTotalNumVGPRs(const MCSubtargetInfo *STI);