[ARM] Use ADDCARRY / SUBCARRY
This is a preparatory step for D34515.
This change:
- makes nodes ISD::ADDCARRY and ISD::SUBCARRY legal for i32
- lowering is done by first converting the boolean value into the carry flag
using (_, C) ← (ARMISD::ADDC R, -1) and converted back to an integer value
using (R, _) ← (ARMISD::ADDE 0, 0, C). An ARMISD::ADDE between the two
operations does the actual addition.
- for subtraction, given that ISD::SUBCARRY second result is actually a
borrow, we need to invert the value of the second operand and result before
and after using ARMISD::SUBE. We need to invert the carry result of
ARMISD::SUBE to preserve the semantics.
- given that the generic combiner may lower ISD::ADDCARRY and
ISD::SUBCARRYinto ISD::UADDO and ISD::USUBO we need to update their lowering
as well otherwise i64 operations now would require branches. This implies
updating the corresponding test for unsigned.
- add new combiner to remove the redundant conversions from/to carry flags
to/from boolean values (ARMISD::ADDC (ARMISD::ADDE 0, 0, C), -1) → C
- fixes PR34045
- fixes PR34564
Differential Revision: https://reviews.llvm.org/D35192
llvm-svn: 313618
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 02fbb1e..79dbdaf 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -802,6 +802,9 @@
setOperationAction(ISD::SSUBO, MVT::i32, Custom);
setOperationAction(ISD::USUBO, MVT::i32, Custom);
+ setOperationAction(ISD::ADDCARRY, MVT::i32, Custom);
+ setOperationAction(ISD::SUBCARRY, MVT::i32, Custom);
+
// i64 operation support.
setOperationAction(ISD::MUL, MVT::i64, Expand);
setOperationAction(ISD::MULHU, MVT::i32, Expand);
@@ -3953,7 +3956,7 @@
}
SDValue
-ARMTargetLowering::LowerXALUO(SDValue Op, SelectionDAG &DAG) const {
+ARMTargetLowering::LowerSignedALUO(SDValue Op, SelectionDAG &DAG) const {
// Let legalize expand this if it isn't a legal type yet.
if (!DAG.getTargetLoweringInfo().isTypeLegal(Op.getValueType()))
return SDValue();
@@ -3975,6 +3978,66 @@
return DAG.getNode(ISD::MERGE_VALUES, dl, VTs, Value, Overflow);
}
+static SDValue ConvertBooleanCarryToCarryFlag(SDValue BoolCarry,
+ SelectionDAG &DAG) {
+ SDLoc DL(BoolCarry);
+ EVT CarryVT = BoolCarry.getValueType();
+
+ APInt NegOne = APInt::getAllOnesValue(CarryVT.getScalarSizeInBits());
+ // This converts the boolean value carry into the carry flag by doing
+ // ARMISD::ADDC Carry, ~0
+ return DAG.getNode(ARMISD::ADDC, DL, DAG.getVTList(CarryVT, MVT::i32),
+ BoolCarry, DAG.getConstant(NegOne, DL, CarryVT));
+}
+
+static SDValue ConvertCarryFlagToBooleanCarry(SDValue Flags, EVT VT,
+ SelectionDAG &DAG) {
+ SDLoc DL(Flags);
+
+ // Now convert the carry flag into a boolean carry. We do this
+ // using ARMISD:ADDE 0, 0, Carry
+ return DAG.getNode(ARMISD::ADDE, DL, DAG.getVTList(VT, MVT::i32),
+ DAG.getConstant(0, DL, MVT::i32),
+ DAG.getConstant(0, DL, MVT::i32), Flags);
+}
+
+SDValue ARMTargetLowering::LowerUnsignedALUO(SDValue Op,
+ SelectionDAG &DAG) const {
+ // Let legalize expand this if it isn't a legal type yet.
+ if (!DAG.getTargetLoweringInfo().isTypeLegal(Op.getValueType()))
+ return SDValue();
+
+ SDValue LHS = Op.getOperand(0);
+ SDValue RHS = Op.getOperand(1);
+ SDLoc dl(Op);
+
+ EVT VT = Op.getValueType();
+ SDVTList VTs = DAG.getVTList(VT, MVT::i32);
+ SDValue Value;
+ SDValue Overflow;
+ switch (Op.getOpcode()) {
+ default:
+ llvm_unreachable("Unknown overflow instruction!");
+ case ISD::UADDO:
+ Value = DAG.getNode(ARMISD::ADDC, dl, VTs, LHS, RHS);
+ // Convert the carry flag into a boolean value.
+ Overflow = ConvertCarryFlagToBooleanCarry(Value.getValue(1), VT, DAG);
+ break;
+ case ISD::USUBO: {
+ Value = DAG.getNode(ARMISD::SUBC, dl, VTs, LHS, RHS);
+ // Convert the carry flag into a boolean value.
+ Overflow = ConvertCarryFlagToBooleanCarry(Value.getValue(1), VT, DAG);
+ // ARMISD::SUBC returns 0 when we have to borrow, so make it an overflow
+ // value. So compute 1 - C.
+ Overflow = DAG.getNode(ISD::SUB, dl, MVT::i32,
+ DAG.getConstant(1, dl, MVT::i32), Overflow);
+ break;
+ }
+ }
+
+ return DAG.getNode(ISD::MERGE_VALUES, dl, VTs, Value, Overflow);
+}
+
SDValue ARMTargetLowering::LowerSELECT(SDValue Op, SelectionDAG &DAG) const {
SDValue Cond = Op.getOperand(0);
SDValue SelectTrue = Op.getOperand(1);
@@ -7380,6 +7443,53 @@
Op.getOperand(1), Op.getOperand(2));
}
+static SDValue LowerADDSUBCARRY(SDValue Op, SelectionDAG &DAG) {
+ SDNode *N = Op.getNode();
+ EVT VT = N->getValueType(0);
+ SDVTList VTs = DAG.getVTList(VT, MVT::i32);
+
+ SDValue Carry = Op.getOperand(2);
+ EVT CarryVT = Carry.getValueType();
+
+ SDLoc DL(Op);
+
+ APInt NegOne = APInt::getAllOnesValue(CarryVT.getScalarSizeInBits());
+
+ SDValue Result;
+ if (Op.getOpcode() == ISD::ADDCARRY) {
+ // This converts the boolean value carry into the carry flag.
+ Carry = ConvertBooleanCarryToCarryFlag(Carry, DAG);
+
+ // Do the addition proper using the carry flag we wanted.
+ Result = DAG.getNode(ARMISD::ADDE, DL, VTs, Op.getOperand(0),
+ Op.getOperand(1), Carry.getValue(1));
+
+ // Now convert the carry flag into a boolean value.
+ Carry = ConvertCarryFlagToBooleanCarry(Result.getValue(1), VT, DAG);
+ } else {
+ // ARMISD::SUBE expects a carry not a borrow like ISD::SUBCARRY so we
+ // have to invert the carry first.
+ Carry = DAG.getNode(ISD::SUB, DL, MVT::i32,
+ DAG.getConstant(1, DL, MVT::i32), Carry);
+ // This converts the boolean value carry into the carry flag.
+ Carry = ConvertBooleanCarryToCarryFlag(Carry, DAG);
+
+ // Do the subtraction proper using the carry flag we wanted.
+ Result = DAG.getNode(ARMISD::SUBE, DL, VTs, Op.getOperand(0),
+ Op.getOperand(1), Carry.getValue(1));
+
+ // Now convert the carry flag into a boolean value.
+ Carry = ConvertCarryFlagToBooleanCarry(Result.getValue(1), VT, DAG);
+ // But the carry returned by ARMISD::SUBE is not a borrow as expected
+ // by ISD::SUBCARRY, so compute 1 - C.
+ Carry = DAG.getNode(ISD::SUB, DL, MVT::i32,
+ DAG.getConstant(1, DL, MVT::i32), Carry);
+ }
+
+ // Return both values.
+ return DAG.getNode(ISD::MERGE_VALUES, DL, N->getVTList(), Result, Carry);
+}
+
SDValue ARMTargetLowering::LowerFSINCOS(SDValue Op, SelectionDAG &DAG) const {
assert(Subtarget->isTargetDarwin());
@@ -7734,11 +7844,14 @@
case ISD::ADDE:
case ISD::SUBC:
case ISD::SUBE: return LowerADDC_ADDE_SUBC_SUBE(Op, DAG);
+ case ISD::ADDCARRY:
+ case ISD::SUBCARRY: return LowerADDSUBCARRY(Op, DAG);
case ISD::SADDO:
- case ISD::UADDO:
case ISD::SSUBO:
+ return LowerSignedALUO(Op, DAG);
+ case ISD::UADDO:
case ISD::USUBO:
- return LowerXALUO(Op, DAG);
+ return LowerUnsignedALUO(Op, DAG);
case ISD::ATOMIC_LOAD:
case ISD::ATOMIC_STORE: return LowerAtomicLoadStore(Op, DAG);
case ISD::FSINCOS: return LowerFSINCOS(Op, DAG);
@@ -9687,11 +9800,11 @@
// a S/UMLAL instruction.
// UMUL_LOHI
// / :lo \ :hi
- // / \ [no multiline comment]
- // loAdd -> ADDE |
- // \ :glue /
- // \ /
- // ADDC <- hiAdd
+ // V \ [no multiline comment]
+ // loAdd -> ADDC |
+ // \ :carry /
+ // V V
+ // ADDE <- hiAdd
//
assert(AddeNode->getOpcode() == ARMISD::ADDE && "Expect an ADDE");
@@ -9699,7 +9812,7 @@
AddeNode->getOperand(2).getValueType() == MVT::i32 &&
"ADDE node has the wrong inputs");
- // Check that we have a glued ADDC node.
+ // Check that we are chained to the right ADDC node.
SDNode* AddcNode = AddeNode->getOperand(2).getNode();
if (AddcNode->getOpcode() != ARMISD::ADDC)
return SDValue();
@@ -9750,7 +9863,7 @@
SDValue* LoMul = nullptr;
SDValue* LowAdd = nullptr;
- // Ensure that ADDE is from high result of ISD::SMUL_LOHI.
+ // Ensure that ADDE is from high result of ISD::xMUL_LOHI.
if ((AddeOp0 != MULOp.getValue(1)) && (AddeOp1 != MULOp.getValue(1)))
return SDValue();
@@ -9775,6 +9888,12 @@
if (!LoMul)
return SDValue();
+ // If HiAdd is the same node as ADDC or is a predecessor of ADDC the
+ // replacement below will create a cycle.
+ if (AddcNode == HiAdd->getNode() ||
+ AddcNode->isPredecessorOf(HiAdd->getNode()))
+ return SDValue();
+
// Create the merged node.
SelectionDAG &DAG = DCI.DAG;
@@ -9877,8 +9996,22 @@
return SDValue();
}
-static SDValue PerformAddcSubcCombine(SDNode *N, SelectionDAG &DAG,
+static SDValue PerformAddcSubcCombine(SDNode *N,
+ TargetLowering::DAGCombinerInfo &DCI,
const ARMSubtarget *Subtarget) {
+ SelectionDAG &DAG(DCI.DAG);
+
+ if (N->getOpcode() == ARMISD::ADDC) {
+ // (ADDC (ADDE 0, 0, C), -1) -> C
+ SDValue LHS = N->getOperand(0);
+ SDValue RHS = N->getOperand(1);
+ if (LHS->getOpcode() == ARMISD::ADDE &&
+ isNullConstant(LHS->getOperand(0)) &&
+ isNullConstant(LHS->getOperand(1)) && isAllOnesConstant(RHS)) {
+ return DCI.CombineTo(N, SDValue(N, 0), LHS->getOperand(2));
+ }
+ }
+
if (Subtarget->isThumb1Only()) {
SDValue RHS = N->getOperand(1);
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(RHS)) {
@@ -11767,6 +11900,14 @@
return SDValue();
}
+static const APInt *isPowerOf2Constant(SDValue V) {
+ ConstantSDNode *C = dyn_cast<ConstantSDNode>(V);
+ if (!C)
+ return nullptr;
+ const APInt *CV = &C->getAPIntValue();
+ return CV->isPowerOf2() ? CV : nullptr;
+}
+
SDValue ARMTargetLowering::PerformCMOVToBFICombine(SDNode *CMOV, SelectionDAG &DAG) const {
// If we have a CMOV, OR and AND combination such as:
// if (x & CN)
@@ -11795,8 +11936,8 @@
SDValue And = CmpZ->getOperand(0);
if (And->getOpcode() != ISD::AND)
return SDValue();
- ConstantSDNode *AndC = dyn_cast<ConstantSDNode>(And->getOperand(1));
- if (!AndC || !AndC->getAPIntValue().isPowerOf2())
+ const APInt *AndC = isPowerOf2Constant(And->getOperand(1));
+ if (!AndC)
return SDValue();
SDValue X = And->getOperand(0);
@@ -11836,7 +11977,7 @@
SDValue V = Y;
SDLoc dl(X);
EVT VT = X.getValueType();
- unsigned BitInX = AndC->getAPIntValue().logBase2();
+ unsigned BitInX = AndC->logBase2();
if (BitInX != 0) {
// We must shift X first.
@@ -11997,7 +12138,7 @@
case ISD::XOR: return PerformXORCombine(N, DCI, Subtarget);
case ISD::AND: return PerformANDCombine(N, DCI, Subtarget);
case ARMISD::ADDC:
- case ARMISD::SUBC: return PerformAddcSubcCombine(N, DCI.DAG, Subtarget);
+ case ARMISD::SUBC: return PerformAddcSubcCombine(N, DCI, Subtarget);
case ARMISD::SUBE: return PerformAddeSubeCombine(N, DCI.DAG, Subtarget);
case ARMISD::BFI: return PerformBFICombine(N, DCI);
case ARMISD::VMOVRRD: return PerformVMOVRRDCombine(N, DCI, Subtarget);
@@ -12713,10 +12854,17 @@
case ARMISD::ADDE:
case ARMISD::SUBC:
case ARMISD::SUBE:
- // These nodes' second result is a boolean
- if (Op.getResNo() == 0)
- break;
- Known.Zero |= APInt::getHighBitsSet(BitWidth, BitWidth - 1);
+ // Special cases when we convert a carry to a boolean.
+ if (Op.getResNo() == 0) {
+ SDValue LHS = Op.getOperand(0);
+ SDValue RHS = Op.getOperand(1);
+ // (ADDE 0, 0, C) will give us a single bit.
+ if (Op->getOpcode() == ARMISD::ADDE && isNullConstant(LHS) &&
+ isNullConstant(RHS)) {
+ Known.Zero |= APInt::getHighBitsSet(BitWidth, BitWidth - 1);
+ return;
+ }
+ }
break;
case ARMISD::CMOV: {
// Bits are known zero/one if known on the LHS and RHS.
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.h b/llvm/lib/Target/ARM/ARMISelLowering.h
index 4836569..61230d9 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.h
+++ b/llvm/lib/Target/ARM/ARMISelLowering.h
@@ -626,7 +626,8 @@
SDValue LowerGlobalTLSAddressWindows(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerGLOBAL_OFFSET_TABLE(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerBR_JT(SDValue Op, SelectionDAG &DAG) const;
- SDValue LowerXALUO(SDValue Op, SelectionDAG &DAG) const;
+ SDValue LowerSignedALUO(SDValue Op, SelectionDAG &DAG) const;
+ SDValue LowerUnsignedALUO(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerSELECT(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerBR_CC(SDValue Op, SelectionDAG &DAG) const;