[Alignment][NFC] Migrate CallingConv tablegen code

[gchatelet]

Summary

We first migrate the generated code, more patches to come.

This patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

[gchatelet]

• Migrate the function taking the ShadowRegList, it's only used by the emitter.

[gchatelet]

rebasing

llvm/include/llvm/CodeGen/CallingConvLower.h

MCRegister AllocateReg(ArrayRef<MCPhysReg> Regs, const MCPhysReg *ShadowRegs) {
     MCRegister Reg = Regs[FirstUnalloc], ShadowReg = ShadowRegs[FirstUnalloc];
     MarkAllocated(Reg);
     MarkAllocated(ShadowReg);
     return Reg;
   }
 
   /// AllocateStack - Allocate a chunk of stack space with the specified size
   /// and alignment.
-  unsigned AllocateStack(unsigned Size, unsigned Alignment) {
-    const Align CheckedAlignment(Alignment);
-    StackOffset = alignTo(StackOffset, CheckedAlignment);
+  unsigned AllocateStack(unsigned Size, Align Alignment) {
+    StackOffset = alignTo(StackOffset, Alignment);
     unsigned Result = StackOffset;
     StackOffset += Size;
-    MaxStackArgAlign = std::max(CheckedAlignment, MaxStackArgAlign);
-    ensureMaxAlignment(CheckedAlignment);
+    MaxStackArgAlign = std::max(Alignment, MaxStackArgAlign);
+    ensureMaxAlignment(Alignment);
     return Result;
   }
 
+  // FIXME: Deprecate this function when transition to Align is over.
+  unsigned AllocateStack(unsigned Size, unsigned Alignment) {
+    return AllocateStack(Size, Align(Alignment));
+  }
+
   void ensureMaxAlignment(Align Alignment) {
     if (!AnalyzingMustTailForwardedRegs)
       MF.getFrameInfo().ensureMaxAlignment(Alignment);
   }
 
   /// Version of AllocateStack with extra register to be shadowed.
   unsigned AllocateStack(unsigned Size, unsigned Align, unsigned ShadowReg) {
     MarkAllocated(ShadowReg);

llvm/utils/TableGen/CallingConvEmitter.cpp

if (Action->isSubClassOf("CCDelegateTo")) {
       if (Size)
         O << Size << ", ";
       else
         O << "\n" << IndentStr
           << "  State.getMachineFunction().getDataLayout()."
              "getTypeAllocSize(EVT(LocVT).getTypeForEVT(State.getContext())),"
              " ";
       if (Align)
-        O << Align;
+        O << "Align(" << Align << ")";
       else
         O << "\n" << IndentStr
           << "  State.getMachineFunction().getDataLayout()."
              "getABITypeAlignment(EVT(LocVT).getTypeForEVT(State.getContext()"
              "))";
       O << ");\n" << IndentStr
         << "State.addLoc(CCValAssign::getMem(ValNo, ValVT, Offset"
         << Counter << ", LocVT, LocInfo));\n";