An empty global constant (one of size 0) may have a section immediately

following it. However, the EmitGlobalConstant method wasn't emitting a body for
the constant. The assembler doesn't like that. Before, we were generating this:

  .zerofill __DATA, __common, __cmd, 1, 3

This fix puts us back to that semantic.

llvm-svn: 95336

2 files changed, 51 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 8456709dbae..31326911590 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1120,6 +1120,7 @@ static void EmitGlobalConstantLargeInt(const ConstantInt *CI,
 void AsmPrinter::EmitGlobalConstant(const Constant *CV, unsigned AddrSpace) {
   if (isa<ConstantAggregateZero>(CV) || isa<UndefValue>(CV)) {
     uint64_t Size = TM.getTargetData()->getTypeAllocSize(CV->getType());
+    if (Size == 0) Size = 1; // An empty "_foo:" followed by a section is undef.
     return OutStreamer.EmitZeros(Size, AddrSpace);
   }
 
diff --git a/llvm/test/CodeGen/PowerPC/2010-02-04-EmptyGlobal.ll b/llvm/test/CodeGen/PowerPC/2010-02-04-EmptyGlobal.ll
new file mode 100644
index 00000000000..56e1f152d04
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/2010-02-04-EmptyGlobal.ll
@@ -0,0 +1,50 @@
+; RUN: llc < %s -mtriple=powerpc-apple-darwin10 -relocation-model=pic -disable-fp-elim | FileCheck %s
+; <rdar://problem/7604010>
+
+%struct.NSString = type opaque
+%struct._DTOpaqueAssertStruct = type { }
+%struct.objc_selector = type opaque
+
+@_cmd = constant %struct._DTOpaqueAssertStruct zeroinitializer ; <%struct._DTOpaqueAssertStruct*> [#uses=1]
+@OBJC_IMAGE_INFO = private constant [2 x i32] zeroinitializer, section "__OBJC, __image_info,regular" ; <[2 x i32]*> [#uses=1]
+@llvm.used = appending global [1 x i8*] [i8* bitcast ([2 x i32]* @OBJC_IMAGE_INFO to i8*)], section "llvm.metadata" ; <[1 x i8*]*> [#uses=0]
+
+define void @_DTAssertionFailureHandler(i8* %objp, i8* %selp, i32 %lineNumber, %struct.NSString* %msgFormat, ...) nounwind ssp {
+entry:
+  %objp_addr = alloca i8*                         ; <i8**> [#uses=1]
+  %selp_addr = alloca i8*                         ; <i8**> [#uses=3]
+  %lineNumber_addr = alloca i32                   ; <i32*> [#uses=1]
+  %msgFormat_addr = alloca %struct.NSString*      ; <%struct.NSString**> [#uses=1]
+  %iftmp.0 = alloca %struct.objc_selector*        ; <%struct.objc_selector**> [#uses=3]
+  %sel = alloca %struct.objc_selector*            ; <%struct.objc_selector**> [#uses=1]
+  %"alloca point" = bitcast i32 0 to i32          ; <i32> [#uses=0]
+  store i8* %objp, i8** %objp_addr
+  store i8* %selp, i8** %selp_addr
+  store i32 %lineNumber, i32* %lineNumber_addr
+  store %struct.NSString* %msgFormat, %struct.NSString** %msgFormat_addr
+  %0 = load i8** %selp_addr, align 4              ; <i8*> [#uses=1]
+  %1 = icmp ne i8* %0, bitcast (%struct._DTOpaqueAssertStruct* @_cmd to i8*) ; <i1> [#uses=1]
+  br i1 %1, label %bb, label %bb1
+
+bb:                                               ; preds = %entry
+  %2 = load i8** %selp_addr, align 4              ; <i8*> [#uses=1]
+  %3 = bitcast i8* %2 to %struct.objc_selector**  ; <%struct.objc_selector**> [#uses=1]
+  %4 = load %struct.objc_selector** %3, align 4   ; <%struct.objc_selector*> [#uses=1]
+  store %struct.objc_selector* %4, %struct.objc_selector** %iftmp.0, align 4
+  br label %bb2
+
+bb1:                                              ; preds = %entry
+  store %struct.objc_selector* null, %struct.objc_selector** %iftmp.0, align 4
+  br label %bb2
+
+bb2:                                              ; preds = %bb1, %bb
+  %5 = load %struct.objc_selector** %iftmp.0, align 4 ; <%struct.objc_selector*> [#uses=1]
+  store %struct.objc_selector* %5, %struct.objc_selector** %sel, align 4
+  br label %return
+
+return:                                           ; preds = %bb2
+  ret void
+
+; CHECK:      __cmd:
+; CHECK-NEXT: .space 1
+}