MC: Add support for .cfi_startproc simple

This commit allows LLVM MC to process .cfi_startproc directives when
they are followed by an additional `simple' identifier. This signals to
elide the emission of target specific CFI instructions that would
normally occur initially.

This fixes PR16587.

Differential Revision: http://llvm-reviews.chandlerc.com/D2624


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200227 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCParser/AsmParser.cpp

@@ -2796,9 +2796,14 @@ bool AsmParser::parseDirectiveCFISections() {
 }
 
 /// parseDirectiveCFIStartProc
-/// ::= .cfi_startproc
+/// ::= .cfi_startproc [simple]
 bool AsmParser::parseDirectiveCFIStartProc() {
-  getStreamer().EmitCFIStartProc();
+  StringRef Simple;
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    if (parseIdentifier(Simple) || Simple != "simple")
+      return TokError("unexpected token in .cfi_startproc directive");
+
+  getStreamer().EmitCFIStartProc(!Simple.empty());
   return false;
 }