[llvm] [TableGen] Introduce RegisterByHwMode (PR #175227)

[Alexander Richardson via llvm-commits]

================
@@ -89,6 +88,23 @@ def : CompressPat<(PTR_MOV PtrRC:$dst, PtrRC:$src),
 // CHECK-NEXT:   switch (MI.getOpcode()) {
 // CHECK-NEXT:   default: return false;
 // CHECK-NEXT:   case MyTarget::PTR_MOV: {
+// CHECK-NEXT:     if (MI.getOperand(1).isReg() &&
+// CHECK-NEXT:         (MI.getOperand(1).getReg() == [](unsigned HwMode) {
+// CHECK-NEXT:           switch (HwMode)
----------------
arichardson wrote:

That's a good point, let me add another test cases where we have a `RegisterByHwMode` that is not specified for all HwModes. Since we only have two here it's fully covered.

https://github.com/llvm/llvm-project/pull/175227