[MC] - Teach llvm-mc to handle comdats whose names are numbers.

[grimar]

Summary

Currently llvm-mc ignores COMDATs whose names are numbers,
for example following code:

.section .foo,"G",@progbits,123,comdat

would produce no COMDATs at all.

Fixes PR35718.

lib/MC/MCParser/ELFAsmParser.cpp

bool ELFAsmParser::parseMergeSize(int64_t &Size) {
   return false;
 }
 
 bool ELFAsmParser::parseGroup(StringRef &GroupName) {
   MCAsmLexer &L = getLexer();
   if (L.isNot(AsmToken::Comma))
     return TokError("expected group name");
   Lex();
-  if (getParser().parseIdentifier(GroupName))
+  if (L.is(AsmToken::Integer)) {
+    GroupName = getTok().getString();
+    Lex();
+  } else if (getParser().parseIdentifier(GroupName)) {
     return true;
+  }
   if (L.is(AsmToken::Comma)) {
     Lex();
     StringRef Linkage;
     if (getParser().parseIdentifier(Linkage))
       return true;
     if (Linkage != "comdat")
       return TokError("Linkage must be 'comdat'");
   }

test/MC/ELF/comdat-name-number.s

+// RUN: llvm-mc -triple x86_64-pc-linux-gnu %s -filetype=obj -o %t.o 
+// RUN: llvm-readobj -elf-section-groups %t.o | FileCheck %s
+
+// Test that we can handle numeric COMDAT names.
+
+.section .foo,"G",@progbits,123,comdat
+.section .bar,"G",@progbits,abc,comdat
+
+// CHECK:      Groups {
+// CHECK-NEXT:   Group {
+// CHECK-NEXT:     Name: .group
+// CHECK-NEXT:     Index:
+// CHECK-NEXT:     Type: COMDAT
+// CHECK-NEXT:     Signature: 123
+// CHECK-NEXT:     Section(s) in group [
+// CHECK-NEXT:       .foo
+// CHECK-NEXT:     ]
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Group {
+// CHECK-NEXT:     Name: .group
+// CHECK-NEXT:     Index:
+// CHECK-NEXT:     Type: COMDAT
+// CHECK-NEXT:     Signature: abc
+// CHECK-NEXT:     Section(s) in group [
+// CHECK-NEXT:       .bar
+// CHECK-NEXT:     ]
+// CHECK-NEXT:   }
+// CHECK-NEXT: }