3 changes, 2 of which are cleanup one of which changes codegen:
1. Rearrange code a bit so that the special case doesn't require indenting lots of code. 2. Add comments describing PPC calling convention. 3. Only round up to 56-bytes of stack space for an outgoing call if the callee is varargs. This saves a bit of stack space. llvm-svn: 28342
This commit is contained in:
Chris Lattner
parent
f058f5aef1
commit
b7552a88d6
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@ -889,120 +889,126 @@ static SDOperand LowerCALL(SDOperand Op, SelectionDAG &DAG) {
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std::vector<SDOperand> args_to_use;
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// Count how many bytes are to be pushed on the stack, including the linkage
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// area, and parameter passing area.
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// area, and parameter passing area. We start with 24 bytes, which is
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// prereserved space for [SP][CR][LR][3 x unused].
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unsigned NumBytes = 24;
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if (Op.getNumOperands() == 5) {
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Chain = DAG.getCALLSEQ_START(Chain, DAG.getConstant(NumBytes, MVT::i32));
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} else {
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for (unsigned i = 5, e = Op.getNumOperands(); i != e; ++i)
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NumBytes += MVT::getSizeInBits(Op.getOperand(i).getValueType())/8;
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// Just to be safe, we'll always reserve the full 24 bytes of linkage area
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// plus 32 bytes of argument space in case any called code gets funky on us.
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// (Required by ABI to support var arg)
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if (NumBytes < 56) NumBytes = 56;
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// Adjust the stack pointer for the new arguments...
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// These operations are automatically eliminated by the prolog/epilog pass
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Chain = DAG.getCALLSEQ_START(Chain,
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DAG.getConstant(NumBytes, MVT::i32));
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// Set up a copy of the stack pointer for use loading and storing any
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// arguments that may not fit in the registers available for argument
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// passing.
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SDOperand StackPtr = DAG.getRegister(PPC::R1, MVT::i32);
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// Figure out which arguments are going to go in registers, and which in
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// memory. Also, if this is a vararg function, floating point operations
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// must be stored to our stack, and loaded into integer regs as well, if
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// any integer regs are available for argument passing.
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unsigned ArgOffset = 24;
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unsigned GPR_remaining = 8;
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unsigned FPR_remaining = 13;
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unsigned VR_remaining = 12;
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// Add up all the space actually used.
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for (unsigned i = 5, e = Op.getNumOperands(); i != e; ++i)
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NumBytes += MVT::getSizeInBits(Op.getOperand(i).getValueType())/8;
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std::vector<SDOperand> MemOps;
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for (unsigned i = 5, e = Op.getNumOperands(); i != e; ++i) {
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SDOperand Arg = Op.getOperand(i);
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// PtrOff will be used to store the current argument to the stack if a
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// register cannot be found for it.
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SDOperand PtrOff = DAG.getConstant(ArgOffset, StackPtr.getValueType());
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PtrOff = DAG.getNode(ISD::ADD, MVT::i32, StackPtr, PtrOff);
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switch (Arg.getValueType()) {
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default: assert(0 && "Unexpected ValueType for argument!");
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case MVT::i32:
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if (GPR_remaining > 0) {
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args_to_use.push_back(Arg);
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--GPR_remaining;
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} else {
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MemOps.push_back(DAG.getNode(ISD::STORE, MVT::Other, Chain,
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Arg, PtrOff, DAG.getSrcValue(NULL)));
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}
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ArgOffset += 4;
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break;
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case MVT::f32:
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case MVT::f64:
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if (FPR_remaining > 0) {
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args_to_use.push_back(Arg);
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--FPR_remaining;
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if (isVarArg) {
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SDOperand Store = DAG.getNode(ISD::STORE, MVT::Other, Chain,
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Arg, PtrOff,
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DAG.getSrcValue(NULL));
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MemOps.push_back(Store);
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// Float varargs are always shadowed in available integer registers
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if (GPR_remaining > 0) {
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SDOperand Load = DAG.getLoad(MVT::i32, Store, PtrOff,
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DAG.getSrcValue(NULL));
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MemOps.push_back(Load.getValue(1));
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args_to_use.push_back(Load);
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--GPR_remaining;
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}
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if (GPR_remaining > 0 && Arg.getValueType() == MVT::f64) {
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SDOperand ConstFour = DAG.getConstant(4, PtrOff.getValueType());
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PtrOff = DAG.getNode(ISD::ADD, MVT::i32, PtrOff, ConstFour);
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SDOperand Load = DAG.getLoad(MVT::i32, Store, PtrOff,
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DAG.getSrcValue(NULL));
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MemOps.push_back(Load.getValue(1));
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args_to_use.push_back(Load);
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--GPR_remaining;
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}
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} else {
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// If we have any FPRs remaining, we may also have GPRs remaining.
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// Args passed in FPRs consume either 1 (f32) or 2 (f64) available
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// GPRs.
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if (GPR_remaining > 0) {
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args_to_use.push_back(DAG.getNode(ISD::UNDEF, MVT::i32));
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--GPR_remaining;
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}
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if (GPR_remaining > 0 && Arg.getValueType() == MVT::f64) {
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args_to_use.push_back(DAG.getNode(ISD::UNDEF, MVT::i32));
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--GPR_remaining;
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}
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// If we are calling what looks like a varargs function on the caller side,
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// there are two cases:
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// 1) The callee uses va_start.
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// 2) The callee doesn't use va_start.
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//
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// In the case of #1, the prolog code will store up to 8 GPR argument
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// registers to the stack, allowing va_start to index over them in memory.
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// Because we cannot tell the difference (on the caller side) between #1/#2,
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// we have to conservatively assume we have #1. As such, make sure we have
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// at least enough stack space for the caller to store the 8 GPRs.
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if (isVarArg && Op.getNumOperands() > 5 && NumBytes < 56)
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NumBytes = 56;
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// Adjust the stack pointer for the new arguments...
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// These operations are automatically eliminated by the prolog/epilog pass
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Chain = DAG.getCALLSEQ_START(Chain,
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DAG.getConstant(NumBytes, MVT::i32));
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// Set up a copy of the stack pointer for use loading and storing any
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// arguments that may not fit in the registers available for argument
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// passing.
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SDOperand StackPtr = DAG.getRegister(PPC::R1, MVT::i32);
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// Figure out which arguments are going to go in registers, and which in
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// memory. Also, if this is a vararg function, floating point operations
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// must be stored to our stack, and loaded into integer regs as well, if
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// any integer regs are available for argument passing.
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unsigned ArgOffset = 24;
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unsigned GPR_remaining = 8;
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unsigned FPR_remaining = 13;
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unsigned VR_remaining = 12;
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std::vector<SDOperand> MemOps;
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for (unsigned i = 5, e = Op.getNumOperands(); i != e; ++i) {
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SDOperand Arg = Op.getOperand(i);
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// PtrOff will be used to store the current argument to the stack if a
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// register cannot be found for it.
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SDOperand PtrOff = DAG.getConstant(ArgOffset, StackPtr.getValueType());
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PtrOff = DAG.getNode(ISD::ADD, MVT::i32, StackPtr, PtrOff);
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switch (Arg.getValueType()) {
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default: assert(0 && "Unexpected ValueType for argument!");
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case MVT::i32:
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if (GPR_remaining > 0) {
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args_to_use.push_back(Arg);
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--GPR_remaining;
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} else {
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MemOps.push_back(DAG.getNode(ISD::STORE, MVT::Other, Chain,
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Arg, PtrOff, DAG.getSrcValue(NULL)));
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}
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ArgOffset += 4;
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break;
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case MVT::f32:
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case MVT::f64:
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if (FPR_remaining > 0) {
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args_to_use.push_back(Arg);
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--FPR_remaining;
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if (isVarArg) {
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SDOperand Store = DAG.getNode(ISD::STORE, MVT::Other, Chain,
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Arg, PtrOff,
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DAG.getSrcValue(NULL));
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MemOps.push_back(Store);
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// Float varargs are always shadowed in available integer registers
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if (GPR_remaining > 0) {
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SDOperand Load = DAG.getLoad(MVT::i32, Store, PtrOff,
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DAG.getSrcValue(NULL));
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MemOps.push_back(Load.getValue(1));
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args_to_use.push_back(Load);
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--GPR_remaining;
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}
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if (GPR_remaining > 0 && Arg.getValueType() == MVT::f64) {
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SDOperand ConstFour = DAG.getConstant(4, PtrOff.getValueType());
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PtrOff = DAG.getNode(ISD::ADD, MVT::i32, PtrOff, ConstFour);
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SDOperand Load = DAG.getLoad(MVT::i32, Store, PtrOff,
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DAG.getSrcValue(NULL));
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MemOps.push_back(Load.getValue(1));
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args_to_use.push_back(Load);
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--GPR_remaining;
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}
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} else {
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MemOps.push_back(DAG.getNode(ISD::STORE, MVT::Other, Chain,
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Arg, PtrOff, DAG.getSrcValue(NULL)));
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// If we have any FPRs remaining, we may also have GPRs remaining.
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// Args passed in FPRs consume either 1 (f32) or 2 (f64) available
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// GPRs.
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if (GPR_remaining > 0) {
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args_to_use.push_back(DAG.getNode(ISD::UNDEF, MVT::i32));
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--GPR_remaining;
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}
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if (GPR_remaining > 0 && Arg.getValueType() == MVT::f64) {
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args_to_use.push_back(DAG.getNode(ISD::UNDEF, MVT::i32));
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--GPR_remaining;
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}
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}
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ArgOffset += (Arg.getValueType() == MVT::f32) ? 4 : 8;
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break;
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case MVT::v4f32:
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case MVT::v4i32:
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case MVT::v8i16:
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case MVT::v16i8:
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assert(!isVarArg && "Don't support passing vectors to varargs yet!");
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assert(VR_remaining &&
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"Don't support passing more than 12 vector args yet!");
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args_to_use.push_back(Arg);
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--VR_remaining;
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break;
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} else {
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MemOps.push_back(DAG.getNode(ISD::STORE, MVT::Other, Chain,
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Arg, PtrOff, DAG.getSrcValue(NULL)));
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}
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ArgOffset += (Arg.getValueType() == MVT::f32) ? 4 : 8;
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break;
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case MVT::v4f32:
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case MVT::v4i32:
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case MVT::v8i16:
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case MVT::v16i8:
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assert(!isVarArg && "Don't support passing vectors to varargs yet!");
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assert(VR_remaining &&
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"Don't support passing more than 12 vector args yet!");
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args_to_use.push_back(Arg);
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--VR_remaining;
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break;
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}
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if (!MemOps.empty())
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Chain = DAG.getNode(ISD::TokenFactor, MVT::Other, MemOps);
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}
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if (!MemOps.empty())
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Chain = DAG.getNode(ISD::TokenFactor, MVT::Other, MemOps);
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std::vector<MVT::ValueType> RetVals(Op.Val->value_begin(),
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Op.Val->value_end());
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