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in X86-64 CCC, i8/i16 arguments are already properly zext/sext'd on input.

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Capture this so that downstream zext/sext's are optimized out.  This
compiles:
  int test(short X) { return (int)X; }

to:

_test:
        movl %edi, %eax
        ret

instead of:

_test:
        movswl %di, %eax
        ret


GCC produces this bizarre code:

_test:
        movw    %di, -12(%rsp)
        movswl  -12(%rsp),%eax
        ret

llvm-svn: 34623
This commit is contained in:
Chris Lattner 2007-02-26 03:18:56 +00:00
parent 0a14efc457
commit 2e7125dc74
1 changed files with 19 additions and 14 deletions
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33
lib/Target/X86/X86ISelLowering.cpp
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@ -1137,12 +1137,6 @@ X86TargetLowering::LowerX86_64CCCArguments(SDOperand Op, SelectionDAG &DAG) {
unsigned NumIntRegs = 0; // Int regs used for parameter passing.
unsigned NumXMMRegs = 0; // XMM regs used for parameter passing.
static const unsigned GPR8ArgRegs[] = {
X86::DIL, X86::SIL, X86::DL, X86::CL, X86::R8B, X86::R9B
};
static const unsigned GPR16ArgRegs[] = {
X86::DI, X86::SI, X86::DX, X86::CX, X86::R8W, X86::R9W
};
static const unsigned GPR32ArgRegs[] = {
X86::EDI, X86::ESI, X86::EDX, X86::ECX, X86::R8D, X86::R9D
};
@ -1156,6 +1150,7 @@ X86TargetLowering::LowerX86_64CCCArguments(SDOperand Op, SelectionDAG &DAG) {
for (unsigned i = 0; i < NumArgs; ++i) {
MVT::ValueType ObjectVT = Op.getValue(i).getValueType();
unsigned ArgFlags = cast<ConstantSDNode>(Op.getOperand(3+i))->getValue();
unsigned ArgIncrement = 8;
unsigned ObjSize = 0;
unsigned ObjIntRegs = 0;
@ -1178,26 +1173,36 @@ X86TargetLowering::LowerX86_64CCCArguments(SDOperand Op, SelectionDAG &DAG) {
case MVT::i64: {
TargetRegisterClass *RC = NULL;
switch (ObjectVT) {
default: break;
default: assert(0 && "Unknown integer VT!");
case MVT::i8:
RC = X86::GR8RegisterClass;
Reg = GPR8ArgRegs[NumIntRegs];
break;
case MVT::i16:
RC = X86::GR16RegisterClass;
Reg = GPR16ArgRegs[NumIntRegs];
break;
case MVT::i32:
RC = X86::GR32RegisterClass;
Reg = GPR32ArgRegs[NumIntRegs];
ArgValue = DAG.getCopyFromReg(Root, Reg, MVT::i32);
break;
case MVT::i64:
RC = X86::GR64RegisterClass;
Reg = GPR64ArgRegs[NumIntRegs];
ArgValue = DAG.getCopyFromReg(Root, Reg, MVT::i64);
break;
}
Reg = AddLiveIn(MF, Reg, RC);
ArgValue = DAG.getCopyFromReg(Root, Reg, ObjectVT);
// If this is an 8 or 16-bit value, it is really passed promoted to 32
// bits. Insert an assert[sz]ext to capture this, then truncate to the
// right size.
if (ObjectVT == MVT::i8 || ObjectVT == MVT::i16) {
// FIXME: FORMAL_ARGUMENTS can't currently distinguish between an
// argument with undefined high bits, so we can't insert a assertzext
// yet.
if (ArgFlags & 1) {
unsigned ExtOpc = (ArgFlags & 1) ? ISD::AssertSext :ISD::AssertZext;
ArgValue = DAG.getNode(ExtOpc, MVT::i32, ArgValue,
DAG.getValueType(ObjectVT));
ArgValue = DAG.getNode(ISD::TRUNCATE, ObjectVT, ArgValue);
}
}
break;
}
case MVT::f32: