[pkg-d-commits] [ldc] 37/211: Decorate thunk target calls as tail-calls (=> jumps)

[Matthias Klumpp]

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mak pushed a commit to annotated tag v1.1.0
in repository ldc.

commit 642d755e998db4e556f65332233a5618b105acee
Author: Martin <noone at nowhere.com>
Date:   Wed Sep 21 19:44:15 2016 +0200

    Decorate thunk target calls as tail-calls (=> jumps)
    
    I noticed that the C++ thunks would adjust the `this` pointer and then
    jump directly to the actual target function.
    The D thunks (on Linux, verified by disassembling) on the other hand
    performed a regular call + return. Requesting tail-calls here leads to
    direct jumps for D thunks as well, improving performance when calling
    virtual functions via interfaces.
---
 ir/irclass.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/ir/irclass.cpp b/ir/irclass.cpp
index 6b4e9fa..44965f8 100644
--- a/ir/irclass.cpp
+++ b/ir/irclass.cpp
@@ -419,15 +419,15 @@ llvm::GlobalVariable *IrAggr::getInterfaceVtbl(BaseClass *b, bool new_instance,
       gIR->DBuilder.EmitStopPoint(fd->loc);
 
       // call the real vtbl function.
-      llvm::CallSite call = gIR->ir->CreateCall(irFunc->func, args);
-      call.setCallingConv(irFunc->func->getCallingConv());
+      llvm::CallInst *call = gIR->ir->CreateCall(irFunc->func, args);
+      call->setCallingConv(irFunc->func->getCallingConv());
+      call->setTailCallKind(llvm::CallInst::TCK_Tail);
 
       // return from the thunk
       if (thunk->getReturnType() == LLType::getVoidTy(gIR->context())) {
         llvm::ReturnInst::Create(gIR->context(), beginbb);
       } else {
-        llvm::ReturnInst::Create(gIR->context(), call.getInstruction(),
-                                 beginbb);
+        llvm::ReturnInst::Create(gIR->context(), call, beginbb);
       }
 
       gIR->DBuilder.EmitFuncEnd(thunkFd);

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