Do not emit a UsedDirective for things in the llvm.used

list that have internal linkage; the linker doesn't need
or want this.  (These objects must still be preserved
at compile time, so just removing them from the llvm.used
list doesn't work.)  Should affect only Darwin.

llvm-svn: 55722

1 files changed, 32 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index dc88da954ab..a720f04a9ae 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -425,8 +425,34 @@ bool AsmPrinter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
   return false;
 }
 
+/// findGlobalValue - if CV is an expression equivalent to a single
+/// global value, return that value.
+const GlobalValue * AsmPrinter::findGlobalValue(const Constant *CV) {
+  if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV))
+    return GV;
+  else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
+    const TargetData *TD = TM.getTargetData();
+    unsigned Opcode = CE->getOpcode();    
+    switch (Opcode) {
+    case Instruction::GetElementPtr: {
+      const Constant *ptrVal = CE->getOperand(0);
+      SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
+      if (TD->getIndexedOffset(ptrVal->getType(), &idxVec[0], idxVec.size()))
+        return 0;
+      return findGlobalValue(ptrVal);
+    }
+    case Instruction::BitCast:
+      return findGlobalValue(CE->getOperand(0));
+    default:
+      return 0;
+    }
+  }
+  return 0;
+}
+
 /// EmitLLVMUsedList - For targets that define a TAI::UsedDirective, mark each
 /// global in the specified llvm.used list as being used with this directive.
+/// Non-globals (i.e. internal linkage) should not be emitted.
 void AsmPrinter::EmitLLVMUsedList(Constant *List) {
   const char *Directive = TAI->getUsedDirective();
 
@@ -435,9 +461,12 @@ void AsmPrinter::EmitLLVMUsedList(Constant *List) {
   if (InitList == 0) return;
   
   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
-    O << Directive;
-    EmitConstantValueOnly(InitList->getOperand(i));
-    O << '\n';
+    const GlobalValue *GV = findGlobalValue(InitList->getOperand(i));
+    if (GV && !GV->hasInternalLinkage()) {
+      O << Directive;
+      EmitConstantValueOnly(InitList->getOperand(i));
+      O << '\n';
+    }
   }
 }