[CodeGen] Report a normal instead of fatal error for label redefinition

[john.brawn]

Summary

A symbol being redefined as a label is something that can happen as a result of ordinary input, so it shouldn't cause a fatal error. Also adjust the error message to match the one you get when a symbol is redefined as a variable.

[MaskRay]

Looks great!

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

 void AsmPrinter::emitFunctionEntryLabel() {
   CurrentFnSym->redefineIfPossible();
 
   // 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->isVariable())
     report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
                        "' is a protected alias");
-  if (CurrentFnSym->isDefined())
-    report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
-                       "' label emitted multiple times to assembly file");
 
   OutStreamer->emitLabel(CurrentFnSym);
 
   if (TM.getTargetTriple().isOSBinFormatELF()) {
     MCSymbol *Sym = getSymbolPreferLocal(MF->getFunction());
     if (Sym != CurrentFnSym)
       OutStreamer->emitLabel(Sym);
   }

llvm/lib/MC/MCStreamer.cpp

void MCStreamer::AssignFragment(MCSymbol *Symbol, MCFragment *Fragment) {
   // be sorted upon later. Zero is reserved to mean 'unemitted'.
   SymbolOrdering[Symbol] = 1 + SymbolOrdering.size();
 }
 
 void MCStreamer::emitLabel(MCSymbol *Symbol, SMLoc Loc) {
   Symbol->redefineIfPossible();
 
   if (!Symbol->isUndefined() || Symbol->isVariable())
-    return getContext().reportError(Loc, "invalid symbol redefinition");
+    return getContext().reportError(Loc, "symbol '" + Twine(Symbol->getName()) +
+                                             "' is already defined");
 
   assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
   assert(getCurrentSectionOnly() && "Cannot emit before setting section!");
   assert(!Symbol->getFragment() && "Unexpected fragment on symbol data!");
   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 
   Symbol->setFragment(&getCurrentSectionOnly()->getDummyFragment());
 

llvm/test/CodeGen/X86/equiv_with_vardef.ll

 ; RUN: not llc -filetype=null %s 2>&1 | FileCheck %s
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 module asm ".equiv var, __var"
 
 @var = global i32 0
 ; CHECK: <unknown>:0: error: symbol 'var' is already defined
-; CHECK: <unknown>:0: error: invalid symbol redefinition
+; CHECK: <unknown>:0: error: symbol 'var' is already defined

llvm/test/CodeGen/X86/label-redefinition.ll

 ; PR7054
-; RUN: not --crash llc %s -o - 2>&1 | grep "'_foo' label emitted multiple times to assembly"
+; RUN: not llc %s -o - 2>&1 | FileCheck %s
 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
 }
 
+; CHECK: <unknown>:0: error: symbol '_foo' is already defined
 define i32 @foo() {
 entry:
   unreachable
 }
 
 declare i32 @xstat64(i32, i8*, i8*)

llvm/test/CodeGen/X86/symbol-redefinition.ll

+; RUN: not llc -mtriple=x86_64-unknown-unknown %s -o - 2>&1 | FileCheck %s
+
+; CHECK: <unknown>:0: error: symbol 'fn' is already defined
+define void @fn() section "fn" {
+  ret void
+}
+
+; CHECK: <unknown>:0: error: symbol 'var' is already defined
+@var = global i32 0, section "var", align 4

llvm/test/CodeGen/XCore/section-name.ll

 ; RUN: not llc < %s -march=xcore -o /dev/null 2>&1 | FileCheck %s
 
 @bar = internal global i32 zeroinitializer
 
 define void @".dp.bss"() {
   ret void
 }
 
-; CHECK: <unknown>:0: error: invalid symbol redefinition
+; CHECK: <unknown>:0: error: symbol '.dp.bss' is already defined

llvm/test/MC/ELF/section-sym-err.s

 // RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o %t.o 2>&1 | FileCheck %s
 
 .section foo
 foo:
 
-// CHECK: error: invalid symbol redefinition
+// CHECK: error: symbol 'foo' is already defined