Fix PR7054 - Assertion `Symbol->isUndefined() && "Cannot define a symbol twice!"' failed.

Users can write broken code that emits the same label twice with asm renaming,
detect this and emit a fatal backend error instead of aborting.

llvm-svn: 103140

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index ded4b3f18bb..47c58d0f0fd 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -408,7 +408,13 @@ void AsmPrinter::EmitFunctionHeader() {
 /// EmitFunctionEntryLabel - Emit the label that is the entrypoint for the
 /// function.  This can be overridden by targets as required to do custom stuff.
 void AsmPrinter::EmitFunctionEntryLabel() {
-  OutStreamer.EmitLabel(CurrentFnSym);
+  // The function label could have already been emitted if two symbols end up
+  // conflicting due to asm renaming.  Detect this and emit an error.
+  if (CurrentFnSym->isUndefined())
+    return OutStreamer.EmitLabel(CurrentFnSym);
+
+  report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
+                     "' label emitted multiple times to assembly file");
 }