diff options
| -rw-r--r-- | contrib/llvm/lib/Target/X86/X86ISelLowering.cpp | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/contrib/llvm/lib/Target/X86/X86ISelLowering.cpp b/contrib/llvm/lib/Target/X86/X86ISelLowering.cpp index 1080925551ea..c3e69e04bbd2 100644 --- a/contrib/llvm/lib/Target/X86/X86ISelLowering.cpp +++ b/contrib/llvm/lib/Target/X86/X86ISelLowering.cpp @@ -2449,15 +2449,21 @@ X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI, RegsToPass.push_back(std::make_pair(unsigned(X86::EBX), DAG.getNode(X86ISD::GlobalBaseReg, DebugLoc(), getPointerTy()))); } else { - // If we are tail calling a global or external symbol in GOT pic mode, we - // cannot use a direct jump, since that would make lazy dynamic linking - // impossible (see PR15086). So pretend this is not a tail call, to - // prevent the optimization to a jump. + // If we are tail calling and generating PIC/GOT style code load the + // address of the callee into ECX. The value in ecx is used as target of + // the tail jump. This is done to circumvent the ebx/callee-saved problem + // for tail calls on PIC/GOT architectures. Normally we would just put the + // address of GOT into ebx and then call target@PLT. But for tail calls + // ebx would be restored (since ebx is callee saved) before jumping to the + // target@PLT. + + // Note: The actual moving to ECX is done further down. GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee); - if ((G && !G->getGlobal()->hasHiddenVisibility() && - !G->getGlobal()->hasProtectedVisibility()) || - isa<ExternalSymbolSDNode>(Callee)) - isTailCall = false; + if (G && !G->getGlobal()->hasHiddenVisibility() && + !G->getGlobal()->hasProtectedVisibility()) + Callee = LowerGlobalAddress(Callee, DAG); + else if (isa<ExternalSymbolSDNode>(Callee)) + Callee = LowerExternalSymbol(Callee, DAG); } } |