From f1968f28869f4e0675450ae39c478a37c5b9abd6 Mon Sep 17 00:00:00 2001
From: Daniel Dunbar <daniel@zuster.org>
Date: Wed, 1 Oct 2008 00:49:24 +0000
Subject: Add simple interface for protecting runtime functions from name
 collisions.  - Provide CodeGenModule::CreateRuntimeFunction which guarantees
 that    the function it creates will have the provided name in the final   
 module. This allows the runtime to have its functions protected    from
 declarations of the same name in the source code.

 - One could argue that this is a reason to abuse the llvm::Module
   namespace for dealing with function redeclarations. However, that
   approach seems conceptually flawed to me. This one also happens to
   be somewhat more efficient.

No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@56899 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CodeGenModule.cpp | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

(limited to 'lib/CodeGen/CodeGenModule.cpp')

diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 6c9999df24..a74f0578a5 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -63,6 +63,7 @@ void CodeGenModule::Release() {
   EmitCtorList(GlobalCtors, "llvm.global_ctors");
   EmitCtorList(GlobalDtors, "llvm.global_dtors");
   EmitAnnotations();
+  BindRuntimeFunctions();
   // Run the verifier to check that the generated code is consistent.
   if (verifyModule(TheModule, llvm::PrintMessageAction)) {
     TheModule.dump();
@@ -70,6 +71,38 @@ void CodeGenModule::Release() {
   }
 }
 
+void CodeGenModule::BindRuntimeFunctions() {
+  // Deal with protecting runtime function names.
+  for (unsigned i = 0, e = RuntimeFunctions.size(); i < e; ++i) {
+    llvm::Function *Fn = RuntimeFunctions[i].first;
+    const std::string &Name = RuntimeFunctions[i].second;
+    
+    // See if there is a conflict against a function.
+    llvm::Function *Conflict = TheModule.getFunction(Name);
+    if (Conflict) {
+      // Decide which version to take. If the conflict is a definition
+      // we are forced to take that, otherwise assume the runtime
+      // knows best.
+      if (!Conflict->isDeclaration()) {
+        llvm::Value *Casted = 
+          llvm::ConstantExpr::getBitCast(Conflict, Fn->getType());
+        Fn->replaceAllUsesWith(Casted);
+        Fn->eraseFromParent();
+      } else {
+        Fn->takeName(Conflict);
+        llvm::Value *Casted = 
+          llvm::ConstantExpr::getBitCast(Fn, Conflict->getType());
+        Conflict->replaceAllUsesWith(Casted);
+        Conflict->eraseFromParent();
+      }
+    } else {
+      // FIXME: There still may be conflicts with aliases and
+      // variables. 
+      Fn->setName(Name);
+    }
+  }
+}
+
 /// ErrorUnsupported - Print out an error that codegen doesn't support the
 /// specified stmt yet.
 void CodeGenModule::ErrorUnsupported(const Stmt *S, const char *Type,
@@ -655,6 +688,16 @@ void CodeGenModule::EmitGlobalFunctionDefinition(const FunctionDecl *D) {
   }
 }
 
+llvm::Function *
+CodeGenModule::CreateRuntimeFunction(const llvm::FunctionType *FTy,
+                                     const std::string &Name) {
+  llvm::Function *Fn = llvm::Function::Create(FTy, 
+                                              llvm::Function::ExternalLinkage,
+                                              "", &TheModule);
+  RuntimeFunctions.push_back(std::make_pair(Fn, Name));
+  return Fn;
+}
+
 void CodeGenModule::UpdateCompletedType(const TagDecl *TD) {
   // Make sure that this type is translated.
   Types.UpdateCompletedType(TD);
-- 
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