[MIR] Fix CFI_INSTRUCTION escape printing

[scott.linder]

Summary

The printer seems to intend to not print the trailing comma but has a
copy-paste error for the last value in the escape, and the parser
enforces having no trailing comma, but somehow a test was never included
to actually confirm it.

[arsenm]

llvm/test/CodeGen/MIR/Generic/cfi-escape.mir

2–3

Don't think you need the intermediate file

10

Don't need the IR section

[scott.linder]

Simplify test

llvm/lib/CodeGen/MachineOperand.cpp

static void printCFI(raw_ostream &OS, const MCCFIInstruction &CFI,
   case MCCFIInstruction::OpEscape: {
     OS << "escape ";
     if (MCSymbol *Label = CFI.getLabel())
       MachineOperand::printSymbol(OS, *Label);
     if (!CFI.getValues().empty()) {
       size_t e = CFI.getValues().size() - 1;
       for (size_t i = 0; i < e; ++i)
         OS << format("0x%02x", uint8_t(CFI.getValues()[i])) << ", ";
-      OS << format("0x%02x", uint8_t(CFI.getValues()[e])) << ", ";
+      OS << format("0x%02x", uint8_t(CFI.getValues()[e]));
     }
     break;
   }
   case MCCFIInstruction::OpUndefined:
     OS << "undefined ";
     if (MCSymbol *Label = CFI.getLabel())
       MachineOperand::printSymbol(OS, *Label);
     printCFIRegister(CFI.getRegister(), OS, TRI);

llvm/test/CodeGen/MIR/AArch64/cfi.mir

bb.0.entry:
     ; CHECK: CFI_INSTRUCTION same_value $w29
     CFI_INSTRUCTION register $w20, $w30
     ; CHECK: CFI_INSTRUCTION register $w20, $w30
     CFI_INSTRUCTION remember_state
     ; CHECK: CFI_INSTRUCTION remember_state
     CFI_INSTRUCTION restore_state
     ; CHECK: CFI_INSTRUCTION restore_state
     CFI_INSTRUCTION escape 0x61, 0x62, 0x63
-    ; CHECK: CFI_INSTRUCTION escape 0x61, 0x62, 0x63
+    ; CHECK: CFI_INSTRUCTION escape 0x61, 0x62, 0x63{{$}}
     CFI_INSTRUCTION window_save
     ; CHECK: CFI_INSTRUCTION window_save
     CFI_INSTRUCTION negate_ra_sign_state
     ; CHECK: CFI_INSTRUCTION negate_ra_sign_state
     RET_ReallyLR

llvm/test/CodeGen/MIR/Generic/cfi-escape.mir

+# RUN: llc -run-pass none -o - %s | llc -x=mir -run-pass none -o - | FileCheck %s
+
+# Check that we don't print a trailing comma for CFI escape indices, and that
+# in general we can round trip them.
+
+name: func
+# CHECK-LABEL: name: func
+body: |
+  bb.0:
+    CFI_INSTRUCTION escape 0x61, 0x62, 0x63
+    ; CHECK: CFI_INSTRUCTION escape 0x61, 0x62, 0x63{{$}}