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

[Matt Arsenault via llvm-commits]

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@@ -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();
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arsenm wrote:

This use is curious, we should only be looking at the number of registers used for return in the calling convention

https://github.com/llvm/llvm-project/pull/157927