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[ARMTargetLowering] ARMISD::{SUB,ADD}{C,E} second result is a boolean implying that upper bits are always 0.

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llvm-svn: 184231
This commit is contained in:
Michael Gottesman 2013-06-18 20:49:45 +00:00
parent dde9797dc2
commit 5a5656f17d
1 changed files with 11 additions and 1 deletions
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12
lib/Target/ARM/ARMISelLowering.cpp
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@ -10184,9 +10184,19 @@ void ARMTargetLowering::computeMaskedBitsForTargetNode(const SDValue Op,
APInt &KnownOne,
const SelectionDAG &DAG,
unsigned Depth) const {
KnownZero = KnownOne = APInt(KnownOne.getBitWidth(), 0);
unsigned BitWidth = KnownOne.getBitWidth();
KnownZero = KnownOne = APInt(BitWidth, 0);
switch (Op.getOpcode()) {
default: break;
case ARMISD::ADDC:
case ARMISD::ADDE:
case ARMISD::SUBC:
case ARMISD::SUBE:
// These nodes' second result is a boolean
if (Op.getResNo() == 0)
break;
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - 1);
break;
case ARMISD::CMOV: {
// Bits are known zero/one if known on the LHS and RHS.
DAG.ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);