[llvm] [AMDGPU] Use SIRegisterInfo to compute used registers. NFCI (PR #149051)

[Matt Arsenault via llvm-commits]

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@@ -139,77 +139,39 @@ AMDGPUResourceUsageAnalysis::analyzeResourceUsage(
 
   Info.UsesVCC =
       MRI.isPhysRegUsed(AMDGPU::VCC_LO) || MRI.isPhysRegUsed(AMDGPU::VCC_HI);
+  Info.NumExplicitSGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::SGPR_32RegClass,
+                                                /*IncludeCalls=*/false);
+  if (ST.hasMAIInsts())
+    Info.NumAGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::AGPR_32RegClass,
+                                          /*IncludeCalls=*/false);
 
   // If there are no calls, MachineRegisterInfo can tell us the used register
   // count easily.
   // A tail call isn't considered a call for MachineFrameInfo's purposes.
   if (!FrameInfo.hasCalls() && !FrameInfo.hasTailCall()) {
-    Info.NumVGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::VGPR_32RegClass);
-    Info.NumExplicitSGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::SGPR_32RegClass);
-    if (ST.hasMAIInsts())
-      Info.NumAGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::AGPR_32RegClass);
+    Info.NumVGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::VGPR_32RegClass,
+                                          /*IncludeCalls=*/false);
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arsenm wrote:

I don't understand why the VGPR case is treated specially under this !hasCalls block. All register classes should be treated equivalently? 

https://github.com/llvm/llvm-project/pull/149051