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Diffstat (limited to 'lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
-rw-r--r--lib/CodeGen/SelectionDAG/DAGCombiner.cpp147
1 files changed, 89 insertions, 58 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 0997840d85..ad8a2279f9 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1535,7 +1535,8 @@ SDOperand DAGCombiner::SimplifyNodeWithTwoResults(SDNode *N, unsigned LoOp,
AddToWorkList(Lo.Val);
SDOperand LoOpt = combine(Lo.Val);
if (LoOpt.Val && LoOpt.Val != Lo.Val &&
- TLI.isOperationLegal(LoOpt.getOpcode(), LoOpt.getValueType()))
+ (!AfterLegalize ||
+ TLI.isOperationLegal(LoOpt.getOpcode(), LoOpt.getValueType())))
return CombineTo(N, LoOpt, LoOpt);
}
@@ -1545,7 +1546,8 @@ SDOperand DAGCombiner::SimplifyNodeWithTwoResults(SDNode *N, unsigned LoOp,
AddToWorkList(Hi.Val);
SDOperand HiOpt = combine(Hi.Val);
if (HiOpt.Val && HiOpt != Hi &&
- TLI.isOperationLegal(HiOpt.getOpcode(), HiOpt.getValueType()))
+ (!AfterLegalize ||
+ TLI.isOperationLegal(HiOpt.getOpcode(), HiOpt.getValueType())))
return CombineTo(N, HiOpt, HiOpt);
}
return SDOperand();
@@ -1736,7 +1738,8 @@ SDOperand DAGCombiner::visitAND(SDNode *N) {
unsigned BitWidth = N1.getValueSizeInBits();
if (DAG.MaskedValueIsZero(N1, APInt::getHighBitsSet(BitWidth,
BitWidth - EVT.getSizeInBits())) &&
- (!AfterLegalize || TLI.isLoadXLegal(ISD::ZEXTLOAD, EVT))) {
+ ((!AfterLegalize && !LN0->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::ZEXTLOAD, EVT))) {
SDOperand ExtLoad = DAG.getExtLoad(ISD::ZEXTLOAD, VT, LN0->getChain(),
LN0->getBasePtr(), LN0->getSrcValue(),
LN0->getSrcValueOffset(), EVT,
@@ -1757,7 +1760,8 @@ SDOperand DAGCombiner::visitAND(SDNode *N) {
unsigned BitWidth = N1.getValueSizeInBits();
if (DAG.MaskedValueIsZero(N1, APInt::getHighBitsSet(BitWidth,
BitWidth - EVT.getSizeInBits())) &&
- (!AfterLegalize || TLI.isLoadXLegal(ISD::ZEXTLOAD, EVT))) {
+ ((!AfterLegalize && !LN0->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::ZEXTLOAD, EVT))) {
SDOperand ExtLoad = DAG.getExtLoad(ISD::ZEXTLOAD, VT, LN0->getChain(),
LN0->getBasePtr(), LN0->getSrcValue(),
LN0->getSrcValueOffset(), EVT,
@@ -1774,18 +1778,19 @@ SDOperand DAGCombiner::visitAND(SDNode *N) {
if (N1C && N0.getOpcode() == ISD::LOAD) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
if (LN0->getExtensionType() != ISD::SEXTLOAD &&
- LN0->isUnindexed() && N0.hasOneUse()) {
+ LN0->isUnindexed() && N0.hasOneUse() &&
+ // Do not change the width of a volatile load.
+ !LN0->isVolatile()) {
MVT EVT = MVT::Other;
uint32_t ActiveBits = N1C->getAPIntValue().getActiveBits();
if (ActiveBits > 0 && APIntOps::isMask(ActiveBits, N1C->getAPIntValue()))
EVT = MVT::getIntegerVT(ActiveBits);
MVT LoadedVT = LN0->getMemoryVT();
- if (EVT != MVT::Other && LoadedVT.bitsGT(EVT) &&
- // Loading a non-byte sized integer is only valid if the extra bits
- // in memory that complete the byte are zero, which is not known here.
- // TODO: remove isSimple check when apint codegen support lands.
- EVT.isSimple() && EVT.isByteSized() &&
+ // Do not generate loads of extended integer types since these can be
+ // expensive (and would be wrong if the type is not byte sized).
+ if (EVT != MVT::Other && LoadedVT.bitsGT(EVT) && EVT.isSimple() &&
+ EVT.isByteSized() && // Exclude MVT::i1, which is simple.
(!AfterLegalize || TLI.isLoadXLegal(ISD::ZEXTLOAD, EVT))) {
MVT PtrType = N0.getOperand(1).getValueType();
// For big endian targets, we need to add an offset to the pointer to
@@ -1957,7 +1962,7 @@ static bool MatchRotateHalf(SDOperand Op, SDOperand &Shift, SDOperand &Mask) {
// idioms for rotate, and if the target supports rotation instructions, generate
// a rot[lr].
SDNode *DAGCombiner::MatchRotate(SDOperand LHS, SDOperand RHS) {
- // Must be a legal type. Expanded an promoted things won't work with rotates.
+ // Must be a legal type. Expanded 'n promoted things won't work with rotates.
MVT VT = LHS.getValueType();
if (!TLI.isTypeLegal(VT)) return 0;
@@ -1965,7 +1970,7 @@ SDNode *DAGCombiner::MatchRotate(SDOperand LHS, SDOperand RHS) {
bool HasROTL = TLI.isOperationLegal(ISD::ROTL, VT);
bool HasROTR = TLI.isOperationLegal(ISD::ROTR, VT);
if (!HasROTL && !HasROTR) return 0;
-
+
// Match "(X shl/srl V1) & V2" where V2 may not be present.
SDOperand LHSShift; // The shift.
SDOperand LHSMask; // AND value if any.
@@ -2385,13 +2390,12 @@ SDOperand DAGCombiner::visitSRA(SDNode *N) {
if (N1C && N0.getOpcode() == ISD::SHL && N1 == N0.getOperand(1)) {
unsigned LowBits = VT.getSizeInBits() - (unsigned)N1C->getValue();
MVT EVT = MVT::getIntegerVT(LowBits);
- // TODO: turn on when apint codegen support lands.
- // if (!AfterLegalize || TLI.isOperationLegal(ISD::SIGN_EXTEND_INREG, EVT))
- if (EVT.isSimple() && TLI.isOperationLegal(ISD::SIGN_EXTEND_INREG, EVT))
+ if (EVT.isSimple() && // TODO: remove when apint codegen support lands.
+ (!AfterLegalize || TLI.isOperationLegal(ISD::SIGN_EXTEND_INREG, EVT)))
return DAG.getNode(ISD::SIGN_EXTEND_INREG, VT, N0.getOperand(0),
DAG.getValueType(EVT));
}
-
+
// fold (sra (sra x, c1), c2) -> (sra x, c1+c2)
if (N1C && N0.getOpcode() == ISD::SRA) {
if (ConstantSDNode *C1 = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
@@ -2417,13 +2421,12 @@ SDOperand DAGCombiner::visitSRA(SDNode *N) {
MVT::getIntegerVT(VTValSize - N1C->getValue());
// Determine the residual right-shift amount.
unsigned ShiftAmt = N1C->getValue() - N01C->getValue();
-
+
// If the shift is not a no-op (in which case this should be just a sign
// extend already), the truncated to type is legal, sign_extend is legal
// on that type, and the the truncate to that type is both legal and free,
// perform the transform.
if (ShiftAmt &&
- TLI.isTypeLegal(TruncVT) &&
TLI.isOperationLegal(ISD::SIGN_EXTEND, TruncVT) &&
TLI.isOperationLegal(ISD::TRUNCATE, VT) &&
TLI.isTruncateFree(VT, TruncVT)) {
@@ -2633,7 +2636,7 @@ SDOperand DAGCombiner::visitSELECT(SDNode *N) {
// If we can fold this based on the true/false value, do so.
if (SimplifySelectOps(N, N1, N2))
return SDOperand(N, 0); // Don't revisit N.
-
+
// fold selects based on a setcc into other things, such as min/max/abs
if (N0.getOpcode() == ISD::SETCC) {
// FIXME:
@@ -2821,7 +2824,8 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
// fold (sext (load x)) -> (sext (truncate (sextload x)))
if (ISD::isNON_EXTLoad(N0.Val) &&
- (!AfterLegalize||TLI.isLoadXLegal(ISD::SEXTLOAD, N0.getValueType()))){
+ ((!AfterLegalize && !cast<LoadSDNode>(N0)->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::SEXTLOAD, N0.getValueType()))) {
bool DoXform = true;
SmallVector<SDNode*, 4> SetCCs;
if (!N0.hasOneUse())
@@ -2862,7 +2866,8 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
ISD::isUNINDEXEDLoad(N0.Val) && N0.hasOneUse()) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
MVT EVT = LN0->getMemoryVT();
- if (!AfterLegalize || TLI.isLoadXLegal(ISD::SEXTLOAD, EVT)) {
+ if ((!AfterLegalize && !LN0->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::SEXTLOAD, EVT)) {
SDOperand ExtLoad = DAG.getExtLoad(ISD::SEXTLOAD, VT, LN0->getChain(),
LN0->getBasePtr(), LN0->getSrcValue(),
LN0->getSrcValueOffset(), EVT,
@@ -2944,7 +2949,8 @@ SDOperand DAGCombiner::visitZERO_EXTEND(SDNode *N) {
// fold (zext (load x)) -> (zext (truncate (zextload x)))
if (ISD::isNON_EXTLoad(N0.Val) &&
- (!AfterLegalize||TLI.isLoadXLegal(ISD::ZEXTLOAD, N0.getValueType()))) {
+ ((!AfterLegalize && !cast<LoadSDNode>(N0)->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::ZEXTLOAD, N0.getValueType()))) {
bool DoXform = true;
SmallVector<SDNode*, 4> SetCCs;
if (!N0.hasOneUse())
@@ -2985,15 +2991,18 @@ SDOperand DAGCombiner::visitZERO_EXTEND(SDNode *N) {
ISD::isUNINDEXEDLoad(N0.Val) && N0.hasOneUse()) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
MVT EVT = LN0->getMemoryVT();
- SDOperand ExtLoad = DAG.getExtLoad(ISD::ZEXTLOAD, VT, LN0->getChain(),
- LN0->getBasePtr(), LN0->getSrcValue(),
- LN0->getSrcValueOffset(), EVT,
- LN0->isVolatile(),
- LN0->getAlignment());
- CombineTo(N, ExtLoad);
- CombineTo(N0.Val, DAG.getNode(ISD::TRUNCATE, N0.getValueType(), ExtLoad),
- ExtLoad.getValue(1));
- return SDOperand(N, 0); // Return N so it doesn't get rechecked!
+ if ((!AfterLegalize && !LN0->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::ZEXTLOAD, EVT)) {
+ SDOperand ExtLoad = DAG.getExtLoad(ISD::ZEXTLOAD, VT, LN0->getChain(),
+ LN0->getBasePtr(), LN0->getSrcValue(),
+ LN0->getSrcValueOffset(), EVT,
+ LN0->isVolatile(),
+ LN0->getAlignment());
+ CombineTo(N, ExtLoad);
+ CombineTo(N0.Val, DAG.getNode(ISD::TRUNCATE, N0.getValueType(), ExtLoad),
+ ExtLoad.getValue(1));
+ return SDOperand(N, 0); // Return N so it doesn't get rechecked!
+ }
}
// zext(setcc x,y,cc) -> select_cc x, y, 1, 0, cc
@@ -3061,7 +3070,8 @@ SDOperand DAGCombiner::visitANY_EXTEND(SDNode *N) {
// fold (aext (load x)) -> (aext (truncate (extload x)))
if (ISD::isNON_EXTLoad(N0.Val) && N0.hasOneUse() &&
- (!AfterLegalize||TLI.isLoadXLegal(ISD::EXTLOAD, N0.getValueType()))) {
+ ((!AfterLegalize && !cast<LoadSDNode>(N0)->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::EXTLOAD, N0.getValueType()))) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
SDOperand ExtLoad = DAG.getExtLoad(ISD::EXTLOAD, VT, LN0->getChain(),
LN0->getBasePtr(), LN0->getSrcValue(),
@@ -3177,11 +3187,12 @@ SDOperand DAGCombiner::ReduceLoadWidth(SDNode *N) {
}
}
- if (ISD::isNON_EXTLoad(N0.Val) && N0.hasOneUse() &&
- // Do not allow folding to a non-byte-sized integer here. These only
- // load correctly if the extra bits in memory that complete the byte
- // are zero, which is not known here.
- VT.isByteSized()) {
+ // Do not generate loads of extended integer types since these can be
+ // expensive (and would be wrong if the type is not byte sized).
+ if (ISD::isNON_EXTLoad(N0.Val) && N0.hasOneUse() && VT.isSimple() &&
+ VT.isByteSized() && // Exclude MVT::i1, which is simple.
+ // Do not change the width of a volatile load.
+ !cast<LoadSDNode>(N0)->isVolatile()) {
assert(N0.getValueType().getSizeInBits() > EVTBits &&
"Cannot truncate to larger type!");
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
@@ -3281,7 +3292,8 @@ SDOperand DAGCombiner::visitSIGN_EXTEND_INREG(SDNode *N) {
if (ISD::isEXTLoad(N0.Val) &&
ISD::isUNINDEXEDLoad(N0.Val) &&
EVT == cast<LoadSDNode>(N0)->getMemoryVT() &&
- (!AfterLegalize || TLI.isLoadXLegal(ISD::SEXTLOAD, EVT))) {
+ ((!AfterLegalize && !cast<LoadSDNode>(N0)->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::SEXTLOAD, EVT))) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
SDOperand ExtLoad = DAG.getExtLoad(ISD::SEXTLOAD, VT, LN0->getChain(),
LN0->getBasePtr(), LN0->getSrcValue(),
@@ -3296,7 +3308,8 @@ SDOperand DAGCombiner::visitSIGN_EXTEND_INREG(SDNode *N) {
if (ISD::isZEXTLoad(N0.Val) && ISD::isUNINDEXEDLoad(N0.Val) &&
N0.hasOneUse() &&
EVT == cast<LoadSDNode>(N0)->getMemoryVT() &&
- (!AfterLegalize || TLI.isLoadXLegal(ISD::SEXTLOAD, EVT))) {
+ ((!AfterLegalize && !cast<LoadSDNode>(N0)->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::SEXTLOAD, EVT))) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
SDOperand ExtLoad = DAG.getExtLoad(ISD::SEXTLOAD, VT, LN0->getChain(),
LN0->getBasePtr(), LN0->getSrcValue(),
@@ -3372,16 +3385,20 @@ SDOperand DAGCombiner::CombineConsecutiveLoads(SDNode *N, MVT VT) {
const MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo();
if (ISD::isNON_EXTLoad(LD2) &&
LD2->hasOneUse() &&
+ // If both are volatile this would reduce the number of volatile loads.
+ // If one is volatile it might be ok, but play conservative and bail out.
+ !cast<LoadSDNode>(LD1)->isVolatile() &&
+ !cast<LoadSDNode>(LD2)->isVolatile() &&
TLI.isConsecutiveLoad(LD2, LD1, LD1VT.getSizeInBits()/8, 1, MFI)) {
LoadSDNode *LD = cast<LoadSDNode>(LD1);
unsigned Align = LD->getAlignment();
unsigned NewAlign = TLI.getTargetMachine().getTargetData()->
getABITypeAlignment(VT.getTypeForMVT());
- if ((!AfterLegalize || TLI.isTypeLegal(VT)) &&
- TLI.isOperationLegal(ISD::LOAD, VT) && NewAlign <= Align)
+ if (NewAlign <= Align &&
+ (!AfterLegalize || TLI.isOperationLegal(ISD::LOAD, VT)))
return DAG.getLoad(VT, LD->getChain(), LD->getBasePtr(),
LD->getSrcValue(), LD->getSrcValueOffset(),
- LD->isVolatile(), Align);
+ false, Align);
}
return SDOperand();
}
@@ -3426,7 +3443,9 @@ SDOperand DAGCombiner::visitBIT_CONVERT(SDNode *N) {
// fold (conv (load x)) -> (load (conv*)x)
// If the resultant load doesn't need a higher alignment than the original!
if (ISD::isNormalLoad(N0.Val) && N0.hasOneUse() &&
- TLI.isOperationLegal(ISD::LOAD, VT)) {
+ // Do not change the width of a volatile load.
+ !cast<LoadSDNode>(N0)->isVolatile() &&
+ (!AfterLegalize || TLI.isOperationLegal(ISD::LOAD, VT))) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
unsigned Align = TLI.getTargetMachine().getTargetData()->
getABITypeAlignment(VT.getTypeForMVT());
@@ -3441,7 +3460,7 @@ SDOperand DAGCombiner::visitBIT_CONVERT(SDNode *N) {
return Load;
}
}
-
+
// Fold bitconvert(fneg(x)) -> xor(bitconvert(x), signbit)
// Fold bitconvert(fabs(x)) -> and(bitconvert(x), ~signbit)
// This often reduces constant pool loads.
@@ -3946,7 +3965,8 @@ SDOperand DAGCombiner::visitFP_EXTEND(SDNode *N) {
// fold (fpext (load x)) -> (fpext (fptrunc (extload x)))
if (ISD::isNON_EXTLoad(N0.Val) && N0.hasOneUse() &&
- (!AfterLegalize||TLI.isLoadXLegal(ISD::EXTLOAD, N0.getValueType()))) {
+ ((!AfterLegalize && !cast<LoadSDNode>(N0)->isVolatile()) ||
+ TLI.isLoadXLegal(ISD::EXTLOAD, N0.getValueType()))) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
SDOperand ExtLoad = DAG.getExtLoad(ISD::EXTLOAD, VT, LN0->getChain(),
LN0->getBasePtr(), LN0->getSrcValue(),
@@ -3960,8 +3980,7 @@ SDOperand DAGCombiner::visitFP_EXTEND(SDNode *N) {
ExtLoad.getValue(1));
return SDOperand(N, 0); // Return N so it doesn't get rechecked!
}
-
-
+
return SDOperand();
}
@@ -4500,7 +4519,7 @@ SDOperand DAGCombiner::visitSTORE(SDNode *N) {
ST->isVolatile(), Align);
}
}
-
+
// If this is a store of a bit convert, store the input value if the
// resultant store does not need a higher alignment than the original.
if (Value.getOpcode() == ISD::BIT_CONVERT && !ST->isTruncatingStore() &&
@@ -4509,13 +4528,19 @@ SDOperand DAGCombiner::visitSTORE(SDNode *N) {
MVT SVT = Value.getOperand(0).getValueType();
unsigned OrigAlign = TLI.getTargetMachine().getTargetData()->
getABITypeAlignment(SVT.getTypeForMVT());
- if (Align <= OrigAlign && TLI.isOperationLegal(ISD::STORE, SVT))
+ if (Align <= OrigAlign &&
+ ((!AfterLegalize && !ST->isVolatile()) ||
+ TLI.isOperationLegal(ISD::STORE, SVT)))
return DAG.getStore(Chain, Value.getOperand(0), Ptr, ST->getSrcValue(),
ST->getSrcValueOffset(), ST->isVolatile(), Align);
}
-
+
// Turn 'store float 1.0, Ptr' -> 'store int 0x12345678, Ptr'
if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(Value)) {
+ // NOTE: If the original store is volatile, this transform must not increase
+ // the number of stores. For example, on x86-32 an f64 can be stored in one
+ // processor operation but an i64 (which is not legal) requires two. So the
+ // transform should not be done in this case.
if (Value.getOpcode() != ISD::TargetConstantFP) {
SDOperand Tmp;
switch (CFP->getValueType(0).getSimpleVT()) {
@@ -4525,7 +4550,8 @@ SDOperand DAGCombiner::visitSTORE(SDNode *N) {
case MVT::ppcf128:
break;
case MVT::f32:
- if (!AfterLegalize || TLI.isTypeLegal(MVT::i32)) {
+ if ((!AfterLegalize && !ST->isVolatile()) ||
+ TLI.isOperationLegal(ISD::STORE, MVT::i32)) {
Tmp = DAG.getConstant((uint32_t)CFP->getValueAPF().
convertToAPInt().getZExtValue(), MVT::i32);
return DAG.getStore(Chain, Tmp, Ptr, ST->getSrcValue(),
@@ -4534,13 +4560,15 @@ SDOperand DAGCombiner::visitSTORE(SDNode *N) {
}
break;
case MVT::f64:
- if (!AfterLegalize || TLI.isTypeLegal(MVT::i64)) {
+ if ((!AfterLegalize && !ST->isVolatile()) ||
+ TLI.isOperationLegal(ISD::STORE, MVT::i64)) {
Tmp = DAG.getConstant(CFP->getValueAPF().convertToAPInt().
getZExtValue(), MVT::i64);
return DAG.getStore(Chain, Tmp, Ptr, ST->getSrcValue(),
ST->getSrcValueOffset(), ST->isVolatile(),
ST->getAlignment());
- } else if (TLI.isTypeLegal(MVT::i32)) {
+ } else if (!ST->isVolatile() &&
+ TLI.isOperationLegal(ISD::STORE, MVT::i32)) {
// Many FP stores are not made apparent until after legalize, e.g. for
// argument passing. Since this is so common, custom legalize the
// 64-bit integer store into two 32-bit stores.
@@ -4638,19 +4666,18 @@ SDOperand DAGCombiner::visitSTORE(SDNode *N) {
return Chain;
}
}
-
+
// If this is an FP_ROUND or TRUNC followed by a store, fold this into a
// truncating store. We can do this even if this is already a truncstore.
if ((Value.getOpcode() == ISD::FP_ROUND || Value.getOpcode() == ISD::TRUNCATE)
- && TLI.isTypeLegal(Value.getOperand(0).getValueType()) &&
- Value.Val->hasOneUse() && ST->isUnindexed() &&
+ && Value.Val->hasOneUse() && ST->isUnindexed() &&
TLI.isTruncStoreLegal(Value.getOperand(0).getValueType(),
ST->getMemoryVT())) {
return DAG.getTruncStore(Chain, Value.getOperand(0), Ptr, ST->getSrcValue(),
ST->getSrcValueOffset(), ST->getMemoryVT(),
ST->isVolatile(), ST->getAlignment());
}
-
+
return SDOperand();
}
@@ -4731,7 +4758,8 @@ SDOperand DAGCombiner::visitEXTRACT_VECTOR_ELT(SDNode *N) {
// original load.
unsigned NewAlign = TLI.getTargetMachine().getTargetData()->
getABITypeAlignment(LVT.getTypeForMVT());
- if (!TLI.isOperationLegal(ISD::LOAD, LVT) || NewAlign > Align)
+ if (NewAlign > Align ||
+ (AfterLegalize && !TLI.isOperationLegal(ISD::LOAD, LVT)))
return SDOperand();
Align = NewAlign;
}
@@ -5136,6 +5164,9 @@ bool DAGCombiner::SimplifySelectOps(SDNode *TheSelect, SDOperand LHS,
// This triggers in things like "select bool X, 10.0, 123.0" after the FP
// constants have been dropped into the constant pool.
if (LHS.getOpcode() == ISD::LOAD &&
+ // Do not let this transformation reduce the number of volatile loads.
+ !cast<LoadSDNode>(LHS)->isVolatile() &&
+ !cast<LoadSDNode>(RHS)->isVolatile() &&
// Token chains must be identical.
LHS.getOperand(0) == RHS.getOperand(0)) {
LoadSDNode *LLD = cast<LoadSDNode>(LHS);