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Fix the (zext (zextload)) case to trigger, similarly for sign extends. 

Allow (zext (truncate)) to apply after legalize if the target supports
AND (which all do).

This compiles
short %foo() {
        %tmp.0 = load ubyte* %X         ; <ubyte> [#uses=1]
        %tmp.3 = cast ubyte %tmp.0 to short             ; <short> [#uses=1]
        ret short %tmp.3
}

to:
_foo:
        movzbl _X, %eax
        ret

instead of:

_foo:
        movzbl _X, %eax
        movzbl %al, %eax
        ret

thanks to Evan for pointing this out.

llvm-svn: 24709
This commit is contained in:
Chris Lattner 2005-12-14 19:05:06 +00:00
parent 8c9e14620f
commit 7dac1083da
1 changed files with 28 additions and 7 deletions
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35
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -1543,9 +1543,6 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
// fold (sext (sext x)) -> (sext x)
if (N0.getOpcode() == ISD::SIGN_EXTEND)
return DAG.getNode(ISD::SIGN_EXTEND, VT, N0.getOperand(0));
// fold (sext (sextload x)) -> (sextload x)
if (N0.getOpcode() == ISD::SEXTLOAD && VT == N0.getValueType())
return N0;
// fold (sext (truncate x)) -> (sextinreg x) iff x size == sext size.
if (N0.getOpcode() == ISD::TRUNCATE && N0.getOperand(0).getValueType() == VT&&
(!AfterLegalize ||
@ -1562,6 +1559,20 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
ExtLoad.getValue(1));
return SDOperand();
}
// fold (sext (sextload x)) -> (sext (truncate (sextload x)))
// fold (sext ( extload x)) -> (sext (truncate (sextload x)))
if ((N0.getOpcode() == ISD::SEXTLOAD || N0.getOpcode() == ISD::EXTLOAD) &&
N0.hasOneUse()) {
SDOperand ExtLoad = DAG.getNode(ISD::SEXTLOAD, VT, N0.getOperand(0),
N0.getOperand(1), N0.getOperand(2),
N0.getOperand(3));
WorkList.push_back(N);
CombineTo(N0.Val, DAG.getNode(ISD::TRUNCATE, N0.getValueType(), ExtLoad),
ExtLoad.getValue(1));
return SDOperand();
}
return SDOperand();
}
@ -1576,12 +1587,9 @@ SDOperand DAGCombiner::visitZERO_EXTEND(SDNode *N) {
// fold (zext (zext x)) -> (zext x)
if (N0.getOpcode() == ISD::ZERO_EXTEND)
return DAG.getNode(ISD::ZERO_EXTEND, VT, N0.getOperand(0));
// fold (zext (zextload x)) -> (zextload x)
if (N0.getOpcode() == ISD::ZEXTLOAD && VT == N0.getValueType())
return N0;
// fold (zext (truncate x)) -> (zextinreg x) iff x size == zext size.
if (N0.getOpcode() == ISD::TRUNCATE && N0.getOperand(0).getValueType() == VT&&
!AfterLegalize)
(!AfterLegalize || TLI.isOperationLegal(ISD::AND, N0.getValueType())))
return DAG.getZeroExtendInReg(N0.getOperand(0), N0.getValueType());
// fold (zext (load x)) -> (zext (truncate (zextload x)))
if (N0.getOpcode() == ISD::LOAD && N0.hasOneUse()) {
@ -1593,6 +1601,19 @@ SDOperand DAGCombiner::visitZERO_EXTEND(SDNode *N) {
ExtLoad.getValue(1));
return SDOperand();
}
// fold (zext (zextload x)) -> (zext (truncate (zextload x)))
// fold (zext ( extload x)) -> (zext (truncate (zextload x)))
if ((N0.getOpcode() == ISD::ZEXTLOAD || N0.getOpcode() == ISD::EXTLOAD) &&
N0.hasOneUse()) {
SDOperand ExtLoad = DAG.getNode(ISD::ZEXTLOAD, VT, N0.getOperand(0),
N0.getOperand(1), N0.getOperand(2),
N0.getOperand(3));
WorkList.push_back(N);
CombineTo(N0.Val, DAG.getNode(ISD::TRUNCATE, N0.getValueType(), ExtLoad),
ExtLoad.getValue(1));
return SDOperand();
}
return SDOperand();
}