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Add support for intermodule tail calls on x86/32bit with
GOT-style position independent code. Before only tail calls to protected/hidden functions within the same module were optimized. Now all function calls are tail call optimized. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47594 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1547,9 +1547,13 @@ SDOperand X86TargetLowering::LowerCALL(SDOperand Op, SelectionDAG &DAG) {
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}
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// ELF / PIC requires GOT in the EBX register before function calls via PLT
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// GOT pointer.
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// Does not work with tail call since ebx is not restored correctly by
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// tailcaller. TODO: at least for x86 - verify for x86-64
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// GOT pointer.
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// If we are tail calling and generating PIC/GOT style code load the address
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// of the callee into ecx. The value in ecx is used as target of the tail
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// jump. This is done to circumvent the ebx/callee-saved problem for tail
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// calls on PIC/GOT architectures. Normally we would just put the address of
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// GOT into ebx and then call target@PLT. But for tail callss ebx would be
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// restored (since ebx is callee saved) before jumping to the target@PLT.
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if (!IsTailCall && !Is64Bit &&
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getTargetMachine().getRelocationModel() == Reloc::PIC_ &&
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Subtarget->isPICStyleGOT()) {
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@ -1557,6 +1561,16 @@ SDOperand X86TargetLowering::LowerCALL(SDOperand Op, SelectionDAG &DAG) {
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DAG.getNode(X86ISD::GlobalBaseReg, getPointerTy()),
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InFlag);
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InFlag = Chain.getValue(1);
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} else if (!Is64Bit && IsTailCall &&
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getTargetMachine().getRelocationModel() == Reloc::PIC_ &&
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Subtarget->isPICStyleGOT() ) {
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// Note: The actual moving to ecx is done further down.
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GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee);
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if (G && !G->getGlobal()->hasHiddenVisibility() &&
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!G->getGlobal()->hasProtectedVisibility())
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Callee = LowerGlobalAddress(Callee, DAG);
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else if (isa<ExternalSymbolSDNode>(Callee))
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Callee = LowerExternalSymbol(Callee,DAG);
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}
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if (Is64Bit && isVarArg) {
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@ -1661,12 +1675,10 @@ SDOperand X86TargetLowering::LowerCALL(SDOperand Op, SelectionDAG &DAG) {
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getTargetMachine().getCodeModel() != CodeModel::Large)
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Callee = DAG.getTargetExternalSymbol(S->getSymbol(), getPointerTy());
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} else if (IsTailCall) {
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assert(Callee.getOpcode() == ISD::LOAD &&
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"Function destination must be loaded into virtual register");
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unsigned Opc = Is64Bit ? X86::R9 : X86::ECX;
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Chain = DAG.getCopyToReg(Chain,
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DAG.getRegister(Opc, getPointerTy()) ,
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DAG.getRegister(Opc, getPointerTy()),
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Callee,InFlag);
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Callee = DAG.getRegister(Opc, getPointerTy());
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// Add register as live out.
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@ -1773,9 +1785,8 @@ SDOperand X86TargetLowering::LowerCALL(SDOperand Op, SelectionDAG &DAG) {
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// provided:
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// * tailcallopt is enabled
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// * caller/callee are fastcc
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// * elf/pic is disabled OR
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// * elf/pic enabled + callee is in module + callee has
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// visibility protected or hidden
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// On X86_64 architecture with GOT-style position independent code only local
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// (within module) calls are supported at the moment.
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// To keep the stack aligned according to platform abi the function
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// GetAlignedArgumentStackSize ensures that argument delta is always multiples
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// of stack alignment. (Dynamic linkers need this - darwin's dyld for example)
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@ -1844,12 +1855,13 @@ bool X86TargetLowering::IsEligibleForTailCallOptimization(SDOperand Call,
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unsigned CalleeCC = cast<ConstantSDNode>(Call.getOperand(1))->getValue();
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if (CalleeCC == CallingConv::Fast && CallerCC == CalleeCC) {
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SDOperand Callee = Call.getOperand(4);
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// On elf/pic %ebx needs to be livein.
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// On x86/32Bit PIC/GOT tail calls are supported.
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if (getTargetMachine().getRelocationModel() != Reloc::PIC_ ||
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!Subtarget->isPICStyleGOT())
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!Subtarget->isPICStyleGOT()|| !Subtarget->is64Bit())
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return true;
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// Can only do local tail calls with PIC.
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// Can only do local tail calls (in same module, hidden or protected) on
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// x86_64 PIC/GOT at the moment.
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if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee))
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return G->getGlobal()->hasHiddenVisibility()
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|| G->getGlobal()->hasProtectedVisibility();
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