on darwin empty functions need to codegen into something of non-zero length,

otherwise labels get incorrectly merged.  We handled this by emitting a 
".byte 0", but this isn't correct on thumb/arm targets where the text segment
needs to be a multiple of 2/4 bytes.  Handle this by emitting a noop.  This
is more gross than it should be because arm/ppc are not fully mc'ized yet.

This fixes rdar://7908505

llvm-svn: 102400

1 files changed, 9 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 6fc883359be..55eec53b4b6 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -585,9 +585,15 @@ void AsmPrinter::EmitFunctionBody() {
   
   // If the function is empty and the object file uses .subsections_via_symbols,
   // then we need to emit *something* to the function body to prevent the
-  // labels from collapsing together.  Just emit a 0 byte.
-  if (MAI->hasSubsectionsViaSymbols() && !HasAnyRealCode)
-    OutStreamer.EmitIntValue(0, 1, 0/*addrspace*/);
+  // labels from collapsing together.  Just emit a noop.
+  if (MAI->hasSubsectionsViaSymbols() && !HasAnyRealCode) {
+    MCInst Noop;
+    TM.getInstrInfo()->getNoopForMachoTarget(Noop);
+    if (Noop.getOpcode())
+      OutStreamer.EmitInstruction(Noop);
+    else  // Target not mc-ized yet.
+      OutStreamer.EmitRawText(StringRef("\tnop\n"));
+  }
   
   // Emit target-specific gunk after the function body.
   EmitFunctionBodyEnd();