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Generate something sensible for an [SU]ADDO op when the overflow/carry flag is

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the conditional for the BRCOND statement. For instance, it will generate:

    addl %eax, %ecx
    jo LOF

instead of

    addl %eax, %ecx
    ; About 10 instructions to compare the signs of LHS, RHS, and sum.
    jl LOF



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60123 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2008-11-26 22:37:40 +00:00
parent ab8b794a78
commit 3fafd93560
4 changed files with 40 additions and 6 deletions
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20
lib/Target/X86/X86ISelLowering.cpp
View File

@ -6150,6 +6150,26 @@ SDValue X86TargetLowering::LowerCTTZ(SDValue Op, SelectionDAG &DAG) {
SDValue X86TargetLowering::LowerXADDO(SDValue Op, SelectionDAG &DAG,
ISD::NodeType NTy) {
SDNode *N = Op.getNode();
for (SDNode::use_iterator I = N->use_begin(), E = N->use_end(); I != E; ++I) {
SDNode *UseNode = *I;
if (UseNode->getOpcode() == ISD::BRCOND) {
// Lower a branch on the overflow/carry flag into a "JO"/"JC"
// instruction. Convert the addition into an actual addition, not just a
// pseudo node.
SDValue LHS = N->getOperand(0);
SDValue RHS = N->getOperand(1);
SDValue Sum = DAG.getNode(ISD::ADD, LHS.getValueType(), LHS, RHS);
SDValue Ops[] = { UseNode->getOperand(2), UseNode->getOperand(0) };
DAG.SelectNodeTo(UseNode, (NTy == ISD::SADDO) ? X86::JO : X86::JC,
MVT::Other, Ops, 2);
return Sum;
}
}
return SDValue();
}

6
lib/Target/X86/X86InstrInfo.cpp
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@ -1382,6 +1382,8 @@ static X86::CondCode GetCondFromBranchOpc(unsigned BrOpc) {
case X86::JNP: return X86::COND_NP;
case X86::JO: return X86::COND_O;
case X86::JNO: return X86::COND_NO;
case X86::JC: return X86::COND_C;
case X86::JNC: return X86::COND_NC;
}
}
@ -1404,6 +1406,8 @@ unsigned X86::GetCondBranchFromCond(X86::CondCode CC) {
case X86::COND_NP: return X86::JNP;
case X86::COND_O: return X86::JO;
case X86::COND_NO: return X86::JNO;
case X86::COND_C: return X86::JC;
case X86::COND_NC: return X86::JNC;
}
}
@ -1428,6 +1432,8 @@ X86::CondCode X86::GetOppositeBranchCondition(X86::CondCode CC) {
case X86::COND_NP: return X86::COND_P;
case X86::COND_O: return X86::COND_NO;
case X86::COND_NO: return X86::COND_O;
case X86::COND_C: return X86::COND_NC;
case X86::COND_NC: return X86::COND_C;
}
}

8
lib/Target/X86/X86InstrInfo.h
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@ -41,9 +41,11 @@ namespace X86 {
COND_NO = 10,
COND_NP = 11,
COND_NS = 12,
COND_O = 13,
COND_P = 14,
COND_S = 15,
COND_NC = 13,
COND_O = 14,
COND_P = 15,
COND_S = 16,
COND_C = 17,
// Artificial condition codes. These are used by AnalyzeBranch
// to indicate a block terminated with two conditional branches to

12
lib/Target/X86/X86InstrInfo.td
View File

@ -235,9 +235,11 @@ def X86_COND_NE : PatLeaf<(i8 9)>;
def X86_COND_NO : PatLeaf<(i8 10)>;
def X86_COND_NP : PatLeaf<(i8 11)>;
def X86_COND_NS : PatLeaf<(i8 12)>;
def X86_COND_O : PatLeaf<(i8 13)>;
def X86_COND_P : PatLeaf<(i8 14)>;
def X86_COND_S : PatLeaf<(i8 15)>;
def X86_COND_NC : PatLeaf<(i8 13)>;
def X86_COND_O : PatLeaf<(i8 14)>;
def X86_COND_P : PatLeaf<(i8 15)>;
def X86_COND_S : PatLeaf<(i8 16)>;
def X86_COND_C : PatLeaf<(i8 17)>;
def i16immSExt8 : PatLeaf<(i16 imm), [{
// i16immSExt8 predicate - True if the 16-bit immediate fits in a 8-bit
@ -449,6 +451,10 @@ def JO : IBr<0x80, (ins brtarget:$dst), "jo\t$dst",
[(X86brcond bb:$dst, X86_COND_O, EFLAGS)]>, TB;
def JNO : IBr<0x81, (ins brtarget:$dst), "jno\t$dst",
[(X86brcond bb:$dst, X86_COND_NO, EFLAGS)]>, TB;
def JC : IBr<0x82, (ins brtarget:$dst), "jc\t$dst",
[(X86brcond bb:$dst, X86_COND_C, EFLAGS)]>, TB;
def JNC : IBr<0x83, (ins brtarget:$dst), "jnc\t$dst",
[(X86brcond bb:$dst, X86_COND_NC, EFLAGS)]>, TB;
} // Uses = [EFLAGS]
//===----------------------------------------------------------------------===//