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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103140 91177308-0d34-0410-b5e6-96231b3b80d8

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");
 }
 
 

test/CodeGen/X86/label-redefinition.ll

@@ -0,0 +1,15 @@
+; PR7054
+; RUN: not llc %s -o - |& grep {'_foo' label emitted multiple times to assembly}
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
+target triple = "i386-apple-darwin10.0.0"
+
+define i32 @"\01_foo"() {
+  unreachable
+}
+
+define i32 @foo() {
+entry:
+  unreachable
+}
+
+declare i32 @xstat64(i32, i8*, i8*)