[llvm] 2dca0b5 - [AsmParser][SystemZ][z/OS] Fix hanging scenario in HLASMAsmParser class

[Anirudh Prasad via llvm-commits]

Author: Anirudh Prasad
Date: 2021-06-28T12:47:08-04:00
New Revision: 2dca0b5a1ce431692136b293fd5f9ecadea31750

URL: https://github.com/llvm/llvm-project/commit/2dca0b5a1ce431692136b293fd5f9ecadea31750
DIFF: https://github.com/llvm/llvm-project/commit/2dca0b5a1ce431692136b293fd5f9ecadea31750.diff

LOG: [AsmParser][SystemZ][z/OS] Fix hanging scenario in HLASMAsmParser class

- In the caller of the overridden `parseStatement` function (i.e. the `AsmParser::Run()`) in the case of an error **and** if we're not at the start of the statement, we "eat" up until the end of the current statement, so we don't have to process it again.
- However, in the HLASMAsmParser class what's happening is that, if an error occurs at the very start of the statement (for example, you invoke the HLASMAsmParser to parse a gnu directive), we will error out, but we never really progress in terms of the next token in the statement to parse. We simply keep looping processing the same error over and over again (partly because we're at the start of the statement)
- To remedy this, when the `parseAsHLASMLabel` function fails, before returning, we "eat" until the end of the statement function, so we don't process it anymore.

Reviewed By: uweigand

Differential Revision: https://reviews.llvm.org/D104869

Added: 
    

Modified: 
    llvm/lib/MC/MCParser/AsmParser.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 5305dde360d4f..1adde169c0a16 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -6302,8 +6302,12 @@ bool HLASMAsmParser::parseStatement(ParseStatementInfo &Info,
   if (ShouldParseAsHLASMLabel) {
     // If there were any errors while handling and emitting the label,
     // early return.
-    if (parseAsHLASMLabel(Info, SI))
+    if (parseAsHLASMLabel(Info, SI)) {
+      // If we know we've failed in parsing, simply eat until end of the
+      // statement. This ensures that we don't process any other statements.
+      eatToEndOfStatement();
       return true;
+    }
   }
 
   return parseAsMachineInstruction(Info, SI);