[llvm] r180202 - Don't produce an empty llvm.compiler.used in LTO.

[Rafael Espindola]

Author: rafael
Date: Wed Apr 24 12:54:35 2013
New Revision: 180202

URL: http://llvm.org/viewvc/llvm-project?rev=180202&view=rev
Log:
Don't produce an empty llvm.compiler.used in LTO.

LTO was always creating an empty llvm.compiler.used. With this patch we
now first check if there is anything to be added first.

Unfortunately, there is no good way to test libLTO in isolation as it needs gold
or ld64, but there are bots doing LTO builds that found this problem.

Modified:
    llvm/trunk/tools/lto/LTOCodeGenerator.cpp

Modified: llvm/trunk/tools/lto/LTOCodeGenerator.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/lto/LTOCodeGenerator.cpp?rev=180202&r1=180201&r2=180202&view=diff
==============================================================================
--- llvm/trunk/tools/lto/LTOCodeGenerator.cpp (original)
+++ llvm/trunk/tools/lto/LTOCodeGenerator.cpp Wed Apr 24 12:54:35 2013
@@ -287,9 +287,7 @@ static void findUsedValues(GlobalVariabl
                            SmallPtrSet<GlobalValue*, 8> &UsedValues) {
   if (LLVMUsed == 0) return;
 
-  ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
-  if (Inits == 0) return;
-
+  ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
     if (GlobalValue *GV =
         dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
@@ -326,23 +324,25 @@ void LTOCodeGenerator::applyScopeRestric
   if (LLVMCompilerUsed)
     LLVMCompilerUsed->eraseFromParent();
 
-  llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
-  std::vector<Constant*> asmUsed2;
-  for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
-         e = asmUsed.end(); i !=e; ++i) {
-    GlobalValue *GV = *i;
-    Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
-    asmUsed2.push_back(c);
-  }
-
-  llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
-  LLVMCompilerUsed =
-    new llvm::GlobalVariable(*mergedModule, ATy, false,
-                             llvm::GlobalValue::AppendingLinkage,
-                             llvm::ConstantArray::get(ATy, asmUsed2),
-                             "llvm.compiler.used");
+  if (!asmUsed.empty()) {
+    llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
+    std::vector<Constant*> asmUsed2;
+    for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
+           e = asmUsed.end(); i !=e; ++i) {
+      GlobalValue *GV = *i;
+      Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
+      asmUsed2.push_back(c);
+    }
+
+    llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
+    LLVMCompilerUsed =
+      new llvm::GlobalVariable(*mergedModule, ATy, false,
+                               llvm::GlobalValue::AppendingLinkage,
+                               llvm::ConstantArray::get(ATy, asmUsed2),
+                               "llvm.compiler.used");
 
-  LLVMCompilerUsed->setSection("llvm.metadata");
+    LLVMCompilerUsed->setSection("llvm.metadata");
+  }
 
   passes.add(createInternalizePass(mustPreserveList));