Do not generate LLVM IR for available_externally function bodies at

-O0, since we won't be using the definitions for anything anyway. For
lib/System/Path.o when built in Debug+Asserts mode, this leads to a 4%
improvement in compile time (and suppresses 440 function bodies).

<rdar://problem/7987644>



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108156 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 5 deletions

diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index cb83ffde6f..d544d4c233 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -817,14 +817,22 @@ void CodeGenModule::EmitGlobalDefinition(GlobalDecl GD) {
     if (Method->isVirtual())
       getVTables().EmitThunks(GD);
 
-  if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(D))
-    return EmitCXXConstructor(CD, GD.getCtorType());
+  if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D)) {
+    // At -O0, don't generate IR for functions with available_externally 
+    // linkage.
+    if (CodeGenOpts.OptimizationLevel == 0 &&
+        getFunctionLinkage(Function) 
+                                  == llvm::Function::AvailableExternallyLinkage)
+      return;
+    
+    if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(Function))
+      return EmitCXXConstructor(CD, GD.getCtorType());
   
-  if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(D))
-    return EmitCXXDestructor(DD, GD.getDtorType());
+    if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(Function))
+      return EmitCXXDestructor(DD, GD.getDtorType());
 
-  if (isa<FunctionDecl>(D))
     return EmitGlobalFunctionDefinition(GD);
+  }
   
   if (const VarDecl *VD = dyn_cast<VarDecl>(D))
     return EmitGlobalVarDefinition(VD);