PR13754: llvm-mc/x86 crashes on .cfi directives without the % prefix for registers.

gas accepts this and it seems to be common enough to be worth supporting. This
doesn't affect the parsing of reg operands outside of .cfi directives.

llvm-svn: 163390

Author: d0k

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

@@ -521,12 +521,13 @@ bool X86AsmParser::isDstOp(X86Operand &Op) {
 bool X86AsmParser::ParseRegister(unsigned &RegNo,
                                  SMLoc &StartLoc, SMLoc &EndLoc) {
   RegNo = 0;
-  if (!isParsingIntelSyntax()) {
-    const AsmToken &TokPercent = Parser.getTok();
-    assert(TokPercent.is(AsmToken::Percent) && "Invalid token kind!");
-    StartLoc = TokPercent.getLoc();
+  const AsmToken &PercentTok = Parser.getTok();
+  StartLoc = PercentTok.getLoc();
+
+  // If we encounter a %, ignore it. This code handles registers with and
+  // without the prefix, unprefixed registers can occur in cfi directives.
+  if (!isParsingIntelSyntax() && PercentTok.is(AsmToken::Percent))
     Parser.Lex(); // Eat percent token.
-  }
 
   const AsmToken &Tok = Parser.getTok();
   if (Tok.isNot(AsmToken::Identifier)) {

llvm/test/MC/ELF/cfi-reg.s

@@ -0,0 +1,18 @@
+// RUN: llvm-mc -triple x86_64-pc-linux-gnu %s -o - | FileCheck %s
+// PR13754
+
+f:
+	.cfi_startproc
+        nop
+	.cfi_offset 6, -16
+        nop
+	.cfi_offset %rsi, -16
+        nop
+	.cfi_offset rbx, -16
+        nop
+	.cfi_endproc
+
+// CHECK: f:
+// CHECK: .cfi_offset %rbp, -16
+// CHECK: .cfi_offset %rsi, -16
+// CHECK: .cfi_offset %rbx, -16