Prevent vregs leaking into the MC layer via TargetRegisterClass::contains()

[dsanders]

Summary

The MC layer doesn't expect to deal with vregs but
TargetRegisterClass::contains() forwards into MCRegisterClass::contains()
and this can cause vregs to turn up in the MC layer APIs. Add guards
against this to prevent this becoming a problem as we replace unsigned
with a new MCRegister object for improved type safety.

[arsenm]

llvm/include/llvm/CodeGen/TargetRegisterInfo.h

90–91

I think this should be a hard assert. Any of the users of this almost certainly do not intend to reach this

[dsanders]

llvm/include/llvm/CodeGen/TargetRegisterInfo.h

90–91

Unfortunately they do expect it at the moment. This is what happens when you make it a hard assert:

Expected Passes    : 31313
Expected Failures  : 154
Unsupported Tests  : 435
Unexpected Failures: 894

It affects Hexagon, X86, ARM, AMDGPU, and AArch64 primarily.

[arsenm]

llvm/include/llvm/CodeGen/TargetRegisterInfo.h

90–91

Should add a FIXME

[dsanders]

• add fixme

[arsenm]

LGTM

llvm/include/llvm/CodeGen/TargetRegisterInfo.h

public:
   /// Return the specified register in the class.
   unsigned getRegister(unsigned i) const {
     return MC->getRegister(i);
   }
 
   /// Return true if the specified register is included in this register class.
   /// This does not include virtual registers.
   bool contains(unsigned Reg) const {
+    /// FIXME: Historically this function has returned false when given vregs
+    ///        but it should probably only receive physical registers
+    if (!Register::isPhysicalRegister(Reg))
+      return false;
     return MC->contains(Reg);
   }
 
   /// Return true if both registers are in this class.
   bool contains(unsigned Reg1, unsigned Reg2) const {
+    /// FIXME: Historically this function has returned false when given a vregs
+    ///        but it should probably only receive physical registers
+    if (!Register::isPhysicalRegister(Reg1) ||
+        !Register::isPhysicalRegister(Reg2))
+      return false;
     return MC->contains(Reg1, Reg2);
   }
 
   /// Return the cost of copying a value between two registers in this class.
   /// A negative number means the register class is very expensive
   /// to copy e.g. status flag register classes.
   int getCopyCost() const { return MC->getCopyCost(); }