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Add support for calls through function pointers in the 64-bit PowerPC SVR4 ABI.

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Patch contributed by Ken Werner of IBM!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91680 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tilmann Scheller
2009-12-18 13:00:15 +00:00
parent 9503b49462
commit 3a84dae654
4 changed files with 141 additions and 3 deletions
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108
lib/Target/PowerPC/PPCISelLowering.cpp
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@@ -419,6 +419,9 @@ const char *PPCTargetLowering::getTargetNodeName(unsigned Opcode) const {
case PPCISD::Hi: return "PPCISD::Hi";
case PPCISD::Lo: return "PPCISD::Lo";
case PPCISD::TOC_ENTRY: return "PPCISD::TOC_ENTRY";
case PPCISD::TOC_RESTORE: return "PPCISD::TOC_RESTORE";
case PPCISD::LOAD: return "PPCISD::LOAD";
case PPCISD::LOAD_TOC: return "PPCISD::LOAD_TOC";
case PPCISD::DYNALLOC: return "PPCISD::DYNALLOC";
case PPCISD::GlobalBaseReg: return "PPCISD::GlobalBaseReg";
case PPCISD::SRL: return "PPCISD::SRL";
@@ -2428,7 +2431,7 @@ unsigned PrepareCall(SelectionDAG &DAG, SDValue &Callee, SDValue &InFlag,
SDValue &Chain, DebugLoc dl, int SPDiff, bool isTailCall,
SmallVector<std::pair<unsigned, SDValue>, 8> &RegsToPass,
SmallVector<SDValue, 8> &Ops, std::vector<EVT> &NodeTys,
bool isSVR4ABI) {
bool isPPC64, bool isSVR4ABI) {
EVT PtrVT = DAG.getTargetLoweringInfo().getPointerTy();
NodeTys.push_back(MVT::Other); // Returns a chain
NodeTys.push_back(MVT::Flag); // Returns a flag for retval copy to use.
@@ -2449,6 +2452,74 @@ unsigned PrepareCall(SelectionDAG &DAG, SDValue &Callee, SDValue &InFlag,
// Otherwise, this is an indirect call. We have to use a MTCTR/BCTRL pair
// to do the call, we can't use PPCISD::CALL.
SDValue MTCTROps[] = {Chain, Callee, InFlag};
if (isSVR4ABI && isPPC64) {
// Function pointers in the 64-bit SVR4 ABI do not point to the function
// entry point, but to the function descriptor (the function entry point
// address is part of the function descriptor though).
// The function descriptor is a three doubleword structure with the
// following fields: function entry point, TOC base address and
// environment pointer.
// Thus for a call through a function pointer, the following actions need
// to be performed:
// 1. Save the TOC of the caller in the TOC save area of its stack
// frame (this is done in LowerCall_Darwin()).
// 2. Load the address of the function entry point from the function
// descriptor.
// 3. Load the TOC of the callee from the function descriptor into r2.
// 4. Load the environment pointer from the function descriptor into
// r11.
// 5. Branch to the function entry point address.
// 6. On return of the callee, the TOC of the caller needs to be
// restored (this is done in FinishCall()).
//
// All those operations are flagged together to ensure that no other
// operations can be scheduled in between. E.g. without flagging the
// operations together, a TOC access in the caller could be scheduled
// between the load of the callee TOC and the branch to the callee, which
// results in the TOC access going through the TOC of the callee instead
// of going through the TOC of the caller, which leads to incorrect code.
// Load the address of the function entry point from the function
// descriptor.
SDVTList VTs = DAG.getVTList(MVT::i64, MVT::Other, MVT::Flag);
SDValue LoadFuncPtr = DAG.getNode(PPCISD::LOAD, dl, VTs, MTCTROps,
InFlag.getNode() ? 3 : 2);
Chain = LoadFuncPtr.getValue(1);
InFlag = LoadFuncPtr.getValue(2);
// Load environment pointer into r11.
// Offset of the environment pointer within the function descriptor.
SDValue PtrOff = DAG.getIntPtrConstant(16);
SDValue AddPtr = DAG.getNode(ISD::ADD, dl, MVT::i64, Callee, PtrOff);
SDValue LoadEnvPtr = DAG.getNode(PPCISD::LOAD, dl, VTs, Chain, AddPtr,
InFlag);
Chain = LoadEnvPtr.getValue(1);
InFlag = LoadEnvPtr.getValue(2);
SDValue EnvVal = DAG.getCopyToReg(Chain, dl, PPC::X11, LoadEnvPtr,
InFlag);
Chain = EnvVal.getValue(0);
InFlag = EnvVal.getValue(1);
// Load TOC of the callee into r2. We are using a target-specific load
// with r2 hard coded, because the result of a target-independent load
// would never go directly into r2, since r2 is a reserved register (which
// prevents the register allocator from allocating it), resulting in an
// additional register being allocated and an unnecessary move instruction
// being generated.
VTs = DAG.getVTList(MVT::Other, MVT::Flag);
SDValue LoadTOCPtr = DAG.getNode(PPCISD::LOAD_TOC, dl, VTs, Chain,
Callee, InFlag);
Chain = LoadTOCPtr.getValue(0);
InFlag = LoadTOCPtr.getValue(1);
MTCTROps[0] = Chain;
MTCTROps[1] = LoadFuncPtr;
MTCTROps[2] = InFlag;
}
Chain = DAG.getNode(PPCISD::MTCTR, dl, NodeTys, MTCTROps,
2 + (InFlag.getNode() != 0));
InFlag = Chain.getValue(1);
@@ -2523,6 +2594,7 @@ PPCTargetLowering::FinishCall(CallingConv::ID CallConv, DebugLoc dl,
SmallVector<SDValue, 8> Ops;
unsigned CallOpc = PrepareCall(DAG, Callee, InFlag, Chain, dl, SPDiff,
isTailCall, RegsToPass, Ops, NodeTys,
PPCSubTarget.isPPC64(),
PPCSubTarget.isSVR4ABI());
// When performing tail call optimization the callee pops its arguments off
@@ -2569,8 +2641,23 @@ PPCTargetLowering::FinishCall(CallingConv::ID CallConv, DebugLoc dl,
// stack frame. If caller and callee belong to the same module (and have the
// same TOC), the NOP will remain unchanged.
if (!isTailCall && PPCSubTarget.isSVR4ABI()&& PPCSubTarget.isPPC64()) {
// Insert NOP.
InFlag = DAG.getNode(PPCISD::NOP, dl, MVT::Flag, InFlag);
SDVTList VTs = DAG.getVTList(MVT::Other, MVT::Flag);
if (CallOpc == PPCISD::BCTRL_SVR4) {
// This is a call through a function pointer.
// Restore the caller TOC from the save area into R2.
// See PrepareCall() for more information about calls through function
// pointers in the 64-bit SVR4 ABI.
// We are using a target-specific load with r2 hard coded, because the
// result of a target-independent load would never go directly into r2,
// since r2 is a reserved register (which prevents the register allocator
// from allocating it), resulting in an additional register being
// allocated and an unnecessary move instruction being generated.
Chain = DAG.getNode(PPCISD::TOC_RESTORE, dl, VTs, Chain, InFlag);
InFlag = Chain.getValue(1);
} else {
// Otherwise insert NOP.
InFlag = DAG.getNode(PPCISD::NOP, dl, MVT::Flag, InFlag);
}
}
Chain = DAG.getCALLSEQ_END(Chain, DAG.getIntPtrConstant(NumBytes, true),
@@ -3123,6 +3210,21 @@ PPCTargetLowering::LowerCall_Darwin(SDValue Chain, SDValue Callee,
Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
&MemOpChains[0], MemOpChains.size());
// Check if this is an indirect call (MTCTR/BCTRL).
// See PrepareCall() for more information about calls through function
// pointers in the 64-bit SVR4 ABI.
if (!isTailCall && isPPC64 && PPCSubTarget.isSVR4ABI() &&
!dyn_cast<GlobalAddressSDNode>(Callee) &&
!dyn_cast<ExternalSymbolSDNode>(Callee) &&
!isBLACompatibleAddress(Callee, DAG)) {
// Load r2 into a virtual register and store it to the TOC save area.
SDValue Val = DAG.getCopyFromReg(Chain, dl, PPC::X2, MVT::i64);
// TOC save area offset.
SDValue PtrOff = DAG.getIntPtrConstant(40);
SDValue AddPtr = DAG.getNode(ISD::ADD, dl, PtrVT, StackPtr, PtrOff);
Chain = DAG.getStore(Val.getValue(1), dl, Val, AddPtr, NULL, 0);
}
// Build a sequence of copy-to-reg nodes chained together with token chain
// and flag operands which copy the outgoing args into the appropriate regs.
SDValue InFlag;