Provide support for preserving assembly comments

Preserve assembly comments from input in output assembly and flags to
toggle property. This is on by default for inline assembly and off in
llvm-mc.

Parsed comments are emitted immediately before an EOL which generally
places them on the expected line.

Reviewers: rtrieu, dwmw2, rnk, majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D20020

llvm-svn: 275058

1 files changed, 12 insertions, 1 deletions

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 9a331ec4458..d16f2452e13 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -626,9 +626,20 @@ const AsmToken &AsmParser::Lex() {
   if (Lexer.getTok().is(AsmToken::Error))
     Error(Lexer.getErrLoc(), Lexer.getErr());
 
+  // if it's a end of statement with a comment in it
+  if (getTok().is(AsmToken::EndOfStatement)) {
+    // if this is a line comment output it.
+    if (getTok().getString().front() != '\n' &&
+        getTok().getString().front() != '\r' && MAI.preserveAsmComments())
+      Out.addExplicitComment(Twine(getTok().getString()));
+  }
+
   const AsmToken *tok = &Lexer.Lex();
-  // Drop comments here.
+
+  // Parse comments here to be deferred until end of next statement.
   while (tok->is(AsmToken::Comment)) {
+    if (MAI.preserveAsmComments())
+      Out.addExplicitComment(Twine(tok->getString()));
     tok = &Lexer.Lex();
   }