Describe stack-id as an enum

This patch changes MIR stack-id from an integer to an enum,
and adds printing/parsing support for this in MIR files. The default
stack-id '0' is now renamed to 'default'.

This should make MIR tests that have stack objects with different stack-ids
more descriptive. It also clarifies code operating on StackID.

Reviewers: arsenm, thegameg, qcolombet

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D60137

llvm-svn: 363533
diff --git a/llvm/lib/Target/AMDGPU/SIFrameLowering.cpp b/llvm/lib/Target/AMDGPU/SIFrameLowering.cpp
index 9571048..f6dadb7 100644
--- a/llvm/lib/Target/AMDGPU/SIFrameLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIFrameLowering.cpp
@@ -544,6 +544,17 @@
   return AMDGPU::NoRegister;
 }
 
+bool SIFrameLowering::isSupportedStackID(TargetStackID::Value ID) const {
+    switch (ID) {
+    default:
+      return false;
+    case TargetStackID::Default:
+    case TargetStackID::NoAlloc:
+    case TargetStackID::SGPRSpill:
+      return true;
+    }
+}
+
 void SIFrameLowering::emitPrologue(MachineFunction &MF,
                                    MachineBasicBlock &MBB) const {
   SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
@@ -762,7 +773,7 @@
 
         if (TII->isSGPRSpill(MI)) {
           int FI = TII->getNamedOperand(MI, AMDGPU::OpName::addr)->getIndex();
-          assert(MFI.getStackID(FI) == SIStackID::SGPR_SPILL);
+          assert(MFI.getStackID(FI) == TargetStackID::SGPRSpill);
           if (FuncInfo->allocateSGPRSpillToVGPR(MF, FI)) {
             bool Spilled = TRI.eliminateSGPRToVGPRSpillFrameIndex(MI, FI, RS);
             (void)Spilled;