[AMDGPU] Use subtarget call to determine number of VGPRs (#157927)

Since the register file was increased that is no longer valid to
call VGPR_32RegClass.getNumregs() to get a total number of arch
registers available on a subtarget.

Fixes: SWDEV-550425

Author: rampitec

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -3452,7 +3452,7 @@ bool SITargetLowering::CanLowerReturn(
 
   // We must use the stack if return would require unavailable registers.
   unsigned MaxNumVGPRs = Subtarget->getMaxNumVGPRs(MF);
-  unsigned TotalNumVGPRs = AMDGPU::VGPR_32RegClass.getNumRegs();
+  unsigned TotalNumVGPRs = Subtarget->getAddressableNumArchVGPRs();
   for (unsigned i = MaxNumVGPRs; i < TotalNumVGPRs; ++i)
     if (CCInfo.isAllocated(AMDGPU::VGPR_32RegClass.getRegister(i)))
       return false;

llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp

@@ -86,7 +86,7 @@ SIMachineFunctionInfo::SIMachineFunctionInfo(const Function &F,
     // FIXME: MayNeedAGPRs is a misnomer for how this is used. MFMA selection
     // should be separated from availability of AGPRs
     if (MFMAVGPRForm ||
-        (ST.getMaxNumVGPRs(F) <= AMDGPU::VGPR_32RegClass.getNumRegs() &&
+        (ST.getMaxNumVGPRs(F) <= ST.getAddressableNumArchVGPRs() &&
          !mayUseAGPRs(F)))
       MayNeedAGPRs = false; // We will select all MAI with VGPR operands.
   }

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

@@ -1399,13 +1399,16 @@ unsigned getTotalNumVGPRs(const MCSubtargetInfo *STI) {
   return IsWave32 ? 1024 : 512;
 }
 
-unsigned getAddressableNumArchVGPRs(const MCSubtargetInfo *STI) { return 256; }
+unsigned getAddressableNumArchVGPRs(const MCSubtargetInfo *STI) {
+  const auto &Features = STI->getFeatureBits();
+  if (Features.test(Feature1024AddressableVGPRs))
+    return Features.test(FeatureWavefrontSize32) ? 1024 : 512;
+  return 256;
+}
 
 unsigned getAddressableNumVGPRs(const MCSubtargetInfo *STI,
                                 unsigned DynamicVGPRBlockSize) {
   const auto &Features = STI->getFeatureBits();
-  if (Features.test(FeatureGFX1250Insts))
-    return Features.test(FeatureWavefrontSize32) ? 1024 : 512;
   if (Features.test(FeatureGFX90AInsts))
     return 512;