AMDGPU: Fix assert on ttmp registers

[arsenm]

Summary

Use register class that does not include them when looking
for unallocated registers.

This is hit by the udiv v8i64 test in the opencl integer
conformance test, and takes a few seconds to compile in
a debug build so no test included.

[• tstellarAMD]

LGTM.

[arsenm]

r269938

lib/Target/AMDGPU/SIFrameLowering.cpp

 
 static bool hasOnlySGPRSpills(const SIMachineFunctionInfo *FuncInfo,
                               const MachineFrameInfo *FrameInfo) {
   return FuncInfo->hasSpilledSGPRs() &&
     (!FuncInfo->hasSpilledVGPRs() && !FuncInfo->hasNonSpillStackObjects());
 }
 
 static ArrayRef<MCPhysReg> getAllSGPR128() {
-  return makeArrayRef(AMDGPU::SReg_128RegClass.begin(),
-                      AMDGPU::SReg_128RegClass.getNumRegs());
+  return makeArrayRef(AMDGPU::SGPR_128RegClass.begin(),
+                      AMDGPU::SGPR_128RegClass.getNumRegs());
 }
 
 static ArrayRef<MCPhysReg> getAllSGPRs() {
   return makeArrayRef(AMDGPU::SGPR_32RegClass.begin(),
                       AMDGPU::SGPR_32RegClass.getNumRegs());
 }
 
 void SIFrameLowering::emitPrologue(MachineFunction &MF,