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Add support for intermodule tail calls on x86/32bit with

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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
This commit is contained in:
Arnold Schwaighofer 2008-02-26 10:21:54 +00:00
parent 865c68188a
commit a2a4b475fc
1 changed files with 24 additions and 12 deletions
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36
lib/Target/X86/X86ISelLowering.cpp
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@ -1547,9 +1547,13 @@ SDOperand X86TargetLowering::LowerCALL(SDOperand Op, SelectionDAG &DAG) {
}
// ELF / PIC requires GOT in the EBX register before function calls via PLT
// GOT pointer.
// Does not work with tail call since ebx is not restored correctly by
// tailcaller. TODO: at least for x86 - verify for x86-64
// GOT pointer.
// 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 callss ebx would be
// restored (since ebx is callee saved) before jumping to the target@PLT.
if (!IsTailCall && !Is64Bit &&
getTargetMachine().getRelocationModel() == Reloc::PIC_ &&
Subtarget->isPICStyleGOT()) {
@ -1557,6 +1561,16 @@ SDOperand X86TargetLowering::LowerCALL(SDOperand Op, SelectionDAG &DAG) {
DAG.getNode(X86ISD::GlobalBaseReg, getPointerTy()),
InFlag);
InFlag = Chain.getValue(1);
} else if (!Is64Bit && IsTailCall &&
getTargetMachine().getRelocationModel() == Reloc::PIC_ &&
Subtarget->isPICStyleGOT() ) {
// Note: The actual moving to ecx is done further down.
GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee);
if (G && !G->getGlobal()->hasHiddenVisibility() &&
!G->getGlobal()->hasProtectedVisibility())
Callee = LowerGlobalAddress(Callee, DAG);
else if (isa<ExternalSymbolSDNode>(Callee))
Callee = LowerExternalSymbol(Callee,DAG);
}
if (Is64Bit && isVarArg) {
@ -1661,12 +1675,10 @@ SDOperand X86TargetLowering::LowerCALL(SDOperand Op, SelectionDAG &DAG) {
getTargetMachine().getCodeModel() != CodeModel::Large)
Callee = DAG.getTargetExternalSymbol(S->getSymbol(), getPointerTy());
} else if (IsTailCall) {
assert(Callee.getOpcode() == ISD::LOAD &&
"Function destination must be loaded into virtual register");
unsigned Opc = Is64Bit ? X86::R9 : X86::ECX;
Chain = DAG.getCopyToReg(Chain,
DAG.getRegister(Opc, getPointerTy()) ,
DAG.getRegister(Opc, getPointerTy()),
Callee,InFlag);
Callee = DAG.getRegister(Opc, getPointerTy());
// Add register as live out.
@ -1773,9 +1785,8 @@ SDOperand X86TargetLowering::LowerCALL(SDOperand Op, SelectionDAG &DAG) {
// provided:
// * tailcallopt is enabled
// * caller/callee are fastcc
// * elf/pic is disabled OR
// * elf/pic enabled + callee is in module + callee has
// visibility protected or hidden
// On X86_64 architecture with GOT-style position independent code only local
// (within module) calls are supported at the moment.
// To keep the stack aligned according to platform abi the function
// GetAlignedArgumentStackSize ensures that argument delta is always multiples
// of stack alignment. (Dynamic linkers need this - darwin's dyld for example)
@ -1844,12 +1855,13 @@ bool X86TargetLowering::IsEligibleForTailCallOptimization(SDOperand Call,
unsigned CalleeCC = cast<ConstantSDNode>(Call.getOperand(1))->getValue();
if (CalleeCC == CallingConv::Fast && CallerCC == CalleeCC) {
SDOperand Callee = Call.getOperand(4);
// On elf/pic %ebx needs to be livein.
// On x86/32Bit PIC/GOT tail calls are supported.
if (getTargetMachine().getRelocationModel() != Reloc::PIC_ ||
!Subtarget->isPICStyleGOT())
!Subtarget->isPICStyleGOT()|| !Subtarget->is64Bit())
return true;
// Can only do local tail calls with PIC.
// Can only do local tail calls (in same module, hidden or protected) on
// x86_64 PIC/GOT at the moment.
if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee))
return G->getGlobal()->hasHiddenVisibility()
|| G->getGlobal()->hasProtectedVisibility();