rustllvm: Add a GetOrInsertFunction wrapper

Fixes issue #1161

Test-case-by: Brian Anderson <banderson@mozilla.com>
Signed-off-by: Haitao Li <lihaitao@gmail.com>

src/comp/lib/llvm.rs

@@ -448,6 +448,8 @@ native "cdecl" mod llvm = "rustllvm" {
     fn LLVMGetNextFunction(Fn: ValueRef) -> ValueRef;
     fn LLVMGetPreviousFunction(Fn: ValueRef) -> ValueRef;
     fn LLVMDeleteFunction(Fn: ValueRef);
+    fn LLVMGetOrInsertFunction(M: ModuleRef, Name: sbuf, FunctionTy: TypeRef)
+       -> ValueRef;
     fn LLVMGetIntrinsicID(Fn: ValueRef) -> uint;
     fn LLVMGetFunctionCallConv(Fn: ValueRef) -> uint;
     fn LLVMSetFunctionCallConv(Fn: ValueRef, CC: uint);

src/comp/middle/trans.rs

@@ -301,7 +301,8 @@ fn log_fn_time(ccx: @crate_ctxt, name: str, start: time::timeval,
 
 fn decl_fn(llmod: ModuleRef, name: str, cc: uint, llty: TypeRef) -> ValueRef {
     let llfn: ValueRef =
-        str::as_buf(name, {|buf| llvm::LLVMAddFunction(llmod, buf, llty) });
+        str::as_buf(name, {|buf|
+            llvm::LLVMGetOrInsertFunction(llmod, buf, llty) });
     llvm::LLVMSetFunctionCallConv(llfn, cc);
     ret llfn;
 }

src/rustllvm/RustWrapper.cpp

@@ -141,3 +141,9 @@ extern "C" void LLVMRustEnableSegmentedStacks() {
   EnableSegmentedStacks = true;
 }
 
+extern "C" LLVMValueRef LLVMGetOrInsertFunction(LLVMModuleRef M,
+                                                const char* Name,
+                                                LLVMTypeRef FunctionTy) {
+  return wrap(unwrap(M)->getOrInsertFunction(Name,
+                                             unwrap<FunctionType>(FunctionTy)));
+}

src/rustllvm/rustllvm.def.in

@@ -364,6 +364,7 @@ LLVMGetNextParam
 LLVMGetNextUse
 LLVMGetNumOperands
 LLVMGetOperand
+LLVMGetOrInsertFunction
 LLVMGetParam
 LLVMGetParamParent
 LLVMGetParamTypes

src/test/run-pass/native-dupe.rs

@@ -0,0 +1,12 @@
+native "cdecl" mod rustrt1 = "rustrt" {
+    fn pin_task();
+}
+
+native "cdecl" mod rustrt2 = "rustrt" {
+    fn pin_task();
+}
+
+fn main() {
+    rustrt1::pin_task();
+    rustrt2::pin_task();
+}