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Emit long comparison against -1 better. Instead of this (x86):

Browse Source 
test2:
        movl 8(%esp), %eax
        notl %eax
        movl 4(%esp), %ecx
        notl %ecx
        orl %eax, %ecx
        cmpl $0, %ecx
        sete %al
        movzbl %al, %eax
        ret

or this (PPC):

_test2:
        nor r2, r4, r4
        nor r3, r3, r3
        or r2, r2, r3
        cntlzw r2, r2
        srwi r3, r2, 5
        blr

Emit this:

test2:
        movl 8(%esp), %eax
        andl 4(%esp), %eax
        cmpl $-1, %eax
        sete %al
        movzbl %al, %eax
        ret

or this:

_test2:
.LBB_test2_0:   ;
        and r2, r4, r3
        cmpwi cr0, r2, -1
        li r3, 1
        li r2, 0
        beq .LBB_test2_2        ;
.LBB_test2_1:   ;
        or r3, r2, r2
.LBB_test2_2:   ;
        blr

it seems like the PPC isel could do better for R32 == -1 case.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21242 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-04-12 01:46:05 +00:00
parent 3b2c1d95a2
commit 08b698e38d
1 changed files with 10 additions and 0 deletions
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10
lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
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@ -750,6 +750,16 @@ SDOperand SelectionDAGLegalize::LegalizeOp(SDOperand Op) {
switch (cast<SetCCSDNode>(Node)->getCondition()) {
case ISD::SETEQ:
case ISD::SETNE:
if (RHSLo == RHSHi)
if (ConstantSDNode *RHSCST = dyn_cast<ConstantSDNode>(RHSLo))
if (RHSCST->isAllOnesValue()) {
// Comparison to -1.
Tmp1 = DAG.getNode(ISD::AND, LHSLo.getValueType(), LHSLo, LHSHi);
Result = DAG.getSetCC(cast<SetCCSDNode>(Node)->getCondition(),
Node->getValueType(0), Tmp1, RHSLo);
break;
}
Tmp1 = DAG.getNode(ISD::XOR, LHSLo.getValueType(), LHSLo, RHSLo);
Tmp2 = DAG.getNode(ISD::XOR, LHSLo.getValueType(), LHSHi, RHSHi);
Tmp1 = DAG.getNode(ISD::OR, Tmp1.getValueType(), Tmp1, Tmp2);