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Compile:

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int %test(ulong *%tmp) {
        %tmp = load ulong* %tmp         ; <ulong> [#uses=1]
        %tmp.mask = shr ulong %tmp, ubyte 50            ; <ulong> [#uses=1]
        %tmp.mask = cast ulong %tmp.mask to ubyte
        %tmp2 = and ubyte %tmp.mask, 3          ; <ubyte> [#uses=1]
        %tmp2 = cast ubyte %tmp2 to int         ; <int> [#uses=1]
        ret int %tmp2
}

to:

_test:
        movl 4(%esp), %eax
        movl 4(%eax), %eax
        shrl $18, %eax
        andl $3, %eax
        ret

instead of:

_test:
        movl 4(%esp), %eax
        movl 4(%eax), %eax
        shrl $18, %eax
        # TRUNCATE movb %al, %al
        andb $3, %al
        movzbl %al, %eax
        ret

llvm-svn: 30558
This commit is contained in:
Chris Lattner 2006-09-21 06:14:31 +00:00
parent eb12877970
commit 34768d5361
1 changed files with 14 additions and 0 deletions
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14
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -1831,6 +1831,20 @@ SDOperand DAGCombiner::visitZERO_EXTEND(SDNode *N) {
return DAG.getZeroExtendInReg(Op, N0.getValueType());
}
// fold (zext (and (trunc x), cst)) -> (and x, cst).
if (N0.getOpcode() == ISD::AND &&
N0.getOperand(0).getOpcode() == ISD::TRUNCATE &&
N0.getOperand(1).getOpcode() == ISD::Constant) {
SDOperand X = N0.getOperand(0).getOperand(0);
if (X.getValueType() < VT) {
X = DAG.getNode(ISD::ANY_EXTEND, VT, X);
} else if (X.getValueType() > VT) {
X = DAG.getNode(ISD::TRUNCATE, VT, X);
}
uint64_t Mask = cast<ConstantSDNode>(N0.getOperand(1))->getValue();
return DAG.getNode(ISD::AND, VT, X, DAG.getConstant(Mask, VT));
}
// fold (zext (load x)) -> (zext (truncate (zextload x)))
if (N0.getOpcode() == ISD::LOAD && N0.hasOneUse() &&
(!AfterLegalize||TLI.isOperationLegal(ISD::ZEXTLOAD, N0.getValueType()))){