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[DAGCombiner] Updated bswap byte offset variable names to be more descriptive. NFC

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As discussed on D32039, use MaskByteOffset to describe the variable and also pull out repeated getOpcode() calls.

llvm-svn: 301193
This commit is contained in:
Simon Pilgrim 2017-04-24 17:05:14 +00:00
parent 837e80758c
commit f059a49a99
1 changed files with 15 additions and 13 deletions
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28
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -3878,27 +3878,29 @@ static bool isBSwapHWordElement(SDValue N, MutableArrayRef<SDNode *> Parts) {
if (Opc != ISD::AND && Opc != ISD::SHL && Opc != ISD::SRL)
return false;
SDValue N0 = N.getOperand(0);
unsigned Opc0 = N0.getOpcode();
ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N.getOperand(1));
if (!N1C)
return false;
unsigned Num;
unsigned MaskByteOffset;
switch (N1C->getZExtValue()) {
default:
return false;
case 0xFF: Num = 0; break;
case 0xFF00: Num = 1; break;
case 0xFF0000: Num = 2; break;
case 0xFF000000: Num = 3; break;
case 0xFF: MaskByteOffset = 0; break;
case 0xFF00: MaskByteOffset = 1; break;
case 0xFF0000: MaskByteOffset = 2; break;
case 0xFF000000: MaskByteOffset = 3; break;
}
// Look for (x & 0xff) << 8 as well as ((x << 8) & 0xff00).
SDValue N0 = N.getOperand(0);
if (Opc == ISD::AND) {
if (Num == 0 || Num == 2) {
if (MaskByteOffset == 0 || MaskByteOffset == 2) {
// (x >> 8) & 0xff
// (x >> 8) & 0xff0000
if (N0.getOpcode() != ISD::SRL)
if (Opc0 != ISD::SRL)
return false;
ConstantSDNode *C = dyn_cast<ConstantSDNode>(N0.getOperand(1));
if (!C || C->getZExtValue() != 8)
@ -3906,7 +3908,7 @@ static bool isBSwapHWordElement(SDValue N, MutableArrayRef<SDNode *> Parts) {
} else {
// (x << 8) & 0xff00
// (x << 8) & 0xff000000
if (N0.getOpcode() != ISD::SHL)
if (Opc0 != ISD::SHL)
return false;
ConstantSDNode *C = dyn_cast<ConstantSDNode>(N0.getOperand(1));
if (!C || C->getZExtValue() != 8)
@ -3915,7 +3917,7 @@ static bool isBSwapHWordElement(SDValue N, MutableArrayRef<SDNode *> Parts) {
} else if (Opc == ISD::SHL) {
// (x & 0xff) << 8
// (x & 0xff0000) << 8
if (Num != 0 && Num != 2)
if (MaskByteOffset != 0 && MaskByteOffset != 2)
return false;
ConstantSDNode *C = dyn_cast<ConstantSDNode>(N.getOperand(1));
if (!C || C->getZExtValue() != 8)
@ -3923,17 +3925,17 @@ static bool isBSwapHWordElement(SDValue N, MutableArrayRef<SDNode *> Parts) {
} else { // Opc == ISD::SRL
// (x & 0xff00) >> 8
// (x & 0xff000000) >> 8
if (Num != 1 && Num != 3)
if (MaskByteOffset != 1 && MaskByteOffset != 3)
return false;
ConstantSDNode *C = dyn_cast<ConstantSDNode>(N.getOperand(1));
if (!C || C->getZExtValue() != 8)
return false;
}
if (Parts[Num])
if (Parts[MaskByteOffset])
return false;
Parts[Num] = N0.getOperand(0).getNode();
Parts[MaskByteOffset] = N0.getOperand(0).getNode();
return true;
}