Implement the __builtin_call_with_static_chain GNU extension.

The extension has the following syntax:

  __builtin_call_with_static_chain(Call, Chain)
  where Call must be a function call expression and Chain must be of pointer type

This extension performs a function call Call with a static chain pointer
Chain passed to the callee in a designated register. This is useful for
calling foreign language functions whose ABI uses static chain pointers
(e.g. to implement closures).

Differential Revision: http://reviews.llvm.org/D6332

llvm-svn: 224167

1 files changed, 11 insertions, 5 deletions

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 9348b174620..782273f8cac 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3049,7 +3049,7 @@ RValue CodeGenFunction::EmitCallExpr(const CallExpr *E,
   const Decl *TargetDecl = E->getCalleeDecl();
   if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(TargetDecl)) {
     if (unsigned builtinID = FD->getBuiltinID())
-      return EmitBuiltinExpr(FD, builtinID, E);
+      return EmitBuiltinExpr(FD, builtinID, E, ReturnValue);
   }
 
   if (const auto *CE = dyn_cast<CXXOperatorCallExpr>(E))
@@ -3286,7 +3286,7 @@ LValue CodeGenFunction::EmitStmtExprLValue(const StmtExpr *E) {
 
 RValue CodeGenFunction::EmitCall(QualType CalleeType, llvm::Value *Callee,
                                  const CallExpr *E, ReturnValueSlot ReturnValue,
-                                 const Decl *TargetDecl) {
+                                 const Decl *TargetDecl, llvm::Value *Chain) {
   // Get the actual function type. The callee type will always be a pointer to
   // function type or a block pointer type.
   assert(CalleeType->isFunctionPointerType() &&
@@ -3351,12 +3351,15 @@ RValue CodeGenFunction::EmitCall(QualType CalleeType, llvm::Value *Callee,
   }
 
   CallArgList Args;
+  if (Chain)
+    Args.add(RValue::get(Builder.CreateBitCast(Chain, CGM.VoidPtrTy)),
+             CGM.getContext().VoidPtrTy);
   EmitCallArgs(Args, dyn_cast<FunctionProtoType>(FnType), E->arg_begin(),
                E->arg_end(), E->getDirectCallee(), /*ParamsToSkip*/ 0,
                ForceColumnInfo);
 
-  const CGFunctionInfo &FnInfo =
-    CGM.getTypes().arrangeFreeFunctionCall(Args, FnType);
+  const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeFreeFunctionCall(
+      Args, FnType, /*isChainCall=*/Chain);
 
   // C99 6.5.2.2p6:
   //   If the expression that denotes the called function has a type
@@ -3375,7 +3378,10 @@ RValue CodeGenFunction::EmitCall(QualType CalleeType, llvm::Value *Callee,
   // through an unprototyped function type works like a *non-variadic*
   // call.  The way we make this work is to cast to the exact type
   // of the promoted arguments.
-  if (isa<FunctionNoProtoType>(FnType)) {
+  //
+  // Chain calls use this same code path to add the invisible chain parameter
+  // to the function type.
+  if (isa<FunctionNoProtoType>(FnType) || Chain) {
     llvm::Type *CalleeTy = getTypes().GetFunctionType(FnInfo);
     CalleeTy = CalleeTy->getPointerTo();
     Callee = Builder.CreateBitCast(Callee, CalleeTy, "callee.knr.cast");