Do not legalize large add with addc/adde, introduce addcarry and do it with uaddo/addcarry

[deadalnix]

Summary

As per discution on how to get better codegen an large int legalization, it became clear that using a glue for the carry was preventing several desirable optimizations. Passing the carry down as a value allow for more flexibility.

[jyknight]

Haven't looked in great detail, but overall looks sane to me.

It'll be great to also eliminate ADDC/ADDE/SUBC/SUBE, instead of adding an alternative method. Oh...and, SETCCE. Will probably need a new variant of that as well?

The FIXME for x86 seems pretty distasteful...

Possibly could handle things by having ADDCARRY A, B, CARRY -> RES, OUTCARRY expand into something along the lines of:

1. Create FLAGS value per CARRY input. (what's best way to spell that? New pseudo-op "setcarry" that expands into "ADD8RI CARRY, 255 -> unused, FLAGS", maybe?)
2. Do addition, using carry frmo flags register, input and output: x86isd::ADC A, B, FLAGS -> RES, OUTFLAGS
3. Grab carry bit from flags register: x86isd::setcc cond_b, OUTFLAGS -> OUTCARRY

Then, have a transform that converts "(setcarry (setcc cond_b FLAGS)) -> FLAGS" into just passing through FLAGS?

include/llvm/CodeGen/ISDOpcodes.h

232

Value should be allowed to come from anywhere, not just uaddo/addcarry, although those would be most common.

[deadalnix]

It'll be great to also eliminate ADDC/ADDE/SUBC/SUBE, instead of adding an alternative method. Oh...and, SETCCE. Will probably need a new variant of that as well?

Yes I think that where we want to go with this, but proceeding incrementally seems to make more sense. My plan was to get the new stuff up, move in tree backend to use it, and then deprecate it/remove it. SETCCE is also on my radar.

The FIXME for x86 seems pretty distasteful...

Yes I was very unhappy with that solution and was hopping for some advice on how to do this better. I'll try your solution and see how it goes. Do you see the setcarry as a generic ISD or as a X86 specific one ?

[deadalnix]

Update the X86 addcarry generation.

[deadalnix]

Fixed all test regressions. Turned out adding proper support for addcarry and uaddo in computeKnownBits was the missing piece.

[RKSimon]

If possible it'd be great to split this down into smaller patches, which might be quicker to review overall.

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

1902

Split this into a separate small patch + tests?

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

2517 ↗

(On Diff #89073)

Could the ISD::UADDO case be split into a separate small patch + tests?

lib/Target/X86/X86ISelLowering.cpp

33951

Again, can this be extracted into its own patch + tests?

[deadalnix]

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

1902

No you get a bunch of regression without these. This is doing the same transforms as for ADDC, so this isn't actually new.

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

2517 ↗

(On Diff #89073)

Same thing, bunch of regression without this.

lib/Target/X86/X86ISelLowering.cpp

33951

Without this, you get an add with a carry, followed by a setb or an sbb instruction to materialise the carry, followed by an add Carry, -1 to regenerate the carry. It's pretty bad.

[RKSimon]

What I meant was to pull out some of the codegen changes into smaller patches with their own tests that can be reviewed and accepted before this patch.

Then make this patch just about the addition of ADDCARRY and SUBCARRY instead of having to handle so many things at once.

[deadalnix]

I see, I can do that, but I'm afraid the test cases will be poor. In this patch the tests cases that exists for ADC are covering the transform, but these tests case can't be leveraged when not using UADDO/ADDCARRY .

[efriedma]

include/llvm/CodeGen/ISDOpcodes.h

236

Please explicitly note that the carry input to SUBCARRY supposed to be the output of USUBO; the "carry" bit is defined differently on some architectures.

[deadalnix]

Extract UADDO changes into D30417 and D30379 .

[deadalnix]

Remove all UADDO/USUBO related changes in their own diff.
Keep only the ADDCARRY/SUBCARRY related code in there.

[deadalnix]

Rebase on top of D30611 and fix related issues.

[deadalnix]

Ping ?

[zvi]

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

516–521

Consider using a SmallVector here.

lib/Target/X86/X86ISelLowering.cpp

22973

I know this also appears at the top of LowerADDC_ADDE_SUBC_SUBE, but why it this check needed?

[deadalnix]

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

516–521

The can only be 2 or 3 element so i think just allocating for 2 on the stack is preferable. This is done in various other places in the codebase already.

lib/Target/X86/X86ISelLowering.cpp

22973

Because in that case, the backend wants to run some extra legalization code before coming back there.

[RKSimon]

A few minors for you to look at

include/llvm/CodeGen/ISDOpcodes.h

235

Please detail the results as well (similar to ADDE/SUBE).

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

7952

Update comment to describe addcarry too.

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

517

This will be clearer with unsigned instead of auto

1277

Mixed use of SDValue and auto.

1764

clang-format

1922

clang-format

[deadalnix]

Update as per comments.

[zvi]

lib/Target/X86/X86ISelLowering.cpp

22973

At the time this code runs, there should not be any illegal types present in the DAG.
So i am asking why is there a need to check for illegal types?

[deadalnix]

lib/Target/X86/X86ISelLowering.cpp

22973

I'm not sure what the X86 backend is doing, but this is clearly happening looking at the -debug output of llc.

[deadalnix]

Ping ?

[RKSimon]

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

516–521

Add explicit SDValue() to initialize Ops[2] ?

1809

Should this be a separate fix?

1911

Should this be added separately? At very least DAGTypeLegalizer::ExpandIntRes_UADDSUBO should be moved as an NFC pre-commit so that diff is more obvious.

lib/Target/X86/X86ISelLowering.cpp

33926

We already have a combineAdd function - this should be named something like combineX86Add

[deadalnix]

Ping

[spatel]

I haven't looked at carry codegen enough to approve, but see inline comments for some nits.

include/llvm/CodeGen/ISDOpcodes.h

215–218

If I'd just stumbled into this code, I'd be confused why we have ADDC and ADDE and ADDCARRY. If the intent is to remove these, please add a 'FIXME' comment here that says we should get rid of these.

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

1928–1930

This is copied from above, but comments are supposed to be full sentences (capital letter, period).
Use 'auto *' with dyn_cast because the type is obvious from the code and variable name.

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

517

I'd call this 'NumOps' or similar. 'C' in LLVM usually means some kind of constant value.

lib/CodeGen/TargetLoweringBase.cpp

913–914

This code comment won't age well. Delete.

lib/Target/X86/X86ISelLowering.cpp

33926

+1 - we definitely do not want function names that only differ in captitalization.

33932

auto -> SDValue

33944

auto -> auto *

[deadalnix]

Comments

[deadalnix]

Ping

[deadalnix]

Ping

[mkazantsev]

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

1761

hasOpCarry? By analogy with hasCarry below.

1918

hasOpCarry?

1945

iff -> if?

[deadalnix]

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

1945

iff is a shorthand for if and only if, to indicate bijection. it is commonly used in the comment int hat file, so I think this is fine.

[deadalnix]

Address comments

[deadalnix]

Ping ?

I'd really would ike to move on with optimizing big integers better and this is gating everything. This needs to move forward.

[RKSimon]

include/llvm/CodeGen/ISDOpcodes.h

215–218

I agree with Sanjay - you need to document the plan for ADDC/SUBC here

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

1918

HasOpCarry (style)

1931

Please unsigned instead of auto for the simple types

1964

SDValue HiOps[3] = { LHSH, RHSH, SDValue() };

lib/Target/X86/X86ISelLowering.cpp

22970

unsigned

22988

SDValue

[deadalnix]

Add a FIXME on ADDC/SUBC to explain they are deprecated in favor of ADDCARRY and SUBCARRY and will be removed in the future.

Replaced several uses of auto with explicit types as per request.

[RKSimon]

I see nothing to stop this being accepted now - does anyone have any further comments?

[spatel]

In D29872#741735, @RKSimon wrote:

I see nothing to stop this being accepted now - does anyone have any further comments?

Having the FIXME note was my main concern...just in case the transition takes longer than expected. I have no other comments.

[deadalnix]

If you guys are good with it, then let's move forward. I have various patches coming based on this, and we start moving backends to use ADDCARRY instead of ADC once it is in.

[RKSimon]

LGTM

include/llvm/CodeGen/ISDOpcodes.h

enum NodeType {
     /// SDIVREM/UDIVREM - Divide two integers and produce both a quotient and
     /// remainder result.
     SDIVREM, UDIVREM,
 
     /// CARRY_FALSE - This node is used when folding other nodes,
     /// like ADDC/SUBC, which indicate the carry result is always false.
     CARRY_FALSE,
 
     /// Carry-setting nodes for multiple precision addition and subtraction.
     /// These nodes take two operands of the same value type, and produce two
     /// results.  The first result is the normal add or sub result, the second
     /// result is the carry flag result.
     ADDC, SUBC,
 
     /// Carry-using nodes for multiple precision addition and subtraction. These
     /// nodes take three operands: The first two are the normal lhs and rhs to
     /// the add or sub, and the third is the input carry flag.  These nodes
     /// produce two results; the normal result of the add or sub, and the output
     /// carry flag.  These nodes both read and write a carry flag to allow them
     /// to them to be chained together for add and sub of arbitrarily large
     /// values.
     ADDE, SUBE,
 
+    /// Carry-using nodes for multiple precision addition and subtraction.
+    /// These nodes take three operands: The first two are the normal lhs and
+    /// rhs to the add or sub, and the third is a boolean indicating if there
+    /// is an incoming carry. The use of this opcode is preferable to adde/sube
+    /// if the target supports it, as the carry is a regular value rather than
+    /// a glue, which allows further optimisation.
+    ADDCARRY, SUBCARRY,
+
     /// RESULT, BOOL = [SU]ADDO(LHS, RHS) - Overflow-aware nodes for addition.
     /// These nodes take two operands: the normal LHS and RHS to the add. They
     /// produce two results: the normal result of the add, and a boolean that
     /// indicates if an overflow occurred (*not* a flag, because it may be store
     /// to memory, etc.).  If the type of the boolean is not i1 then the high
     /// bits conform to getBooleanContents.
     /// These nodes are generated from llvm.[su]add.with.overflow intrinsics.
     SADDO, UADDO,

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

private:
     //   otherwise              - N should be replaced by the returned Operand.
     //
     SDValue visitTokenFactor(SDNode *N);
     SDValue visitMERGE_VALUES(SDNode *N);
     SDValue visitADD(SDNode *N);
     SDValue visitADDLike(SDValue N0, SDValue N1, SDNode *LocReference);
     SDValue visitSUB(SDNode *N);
     SDValue visitADDC(SDNode *N);
+    SDValue visitUADDO(SDNode *N);
     SDValue visitSUBC(SDNode *N);
     SDValue visitADDE(SDNode *N);
+    SDValue visitADDCARRY(SDNode *N);
     SDValue visitSUBE(SDNode *N);
     SDValue visitMUL(SDNode *N);
     SDValue useDivRem(SDNode *N);
     SDValue visitSDIV(SDNode *N);
     SDValue visitUDIV(SDNode *N);
     SDValue visitREM(SDNode *N);
     SDValue visitMULHU(SDNode *N);
     SDValue visitMULHS(SDNode *N);

 SDValue DAGCombiner::visit(SDNode *N) {
   switch (N->getOpcode()) {
   default: break;
   case ISD::TokenFactor:        return visitTokenFactor(N);
   case ISD::MERGE_VALUES:       return visitMERGE_VALUES(N);
   case ISD::ADD:                return visitADD(N);
   case ISD::SUB:                return visitSUB(N);
   case ISD::ADDC:               return visitADDC(N);
+  case ISD::UADDO:              return visitUADDO(N);
   case ISD::SUBC:               return visitSUBC(N);
   case ISD::ADDE:               return visitADDE(N);
+  case ISD::ADDCARRY:           return visitADDCARRY(N);
   case ISD::SUBE:               return visitSUBE(N);
   case ISD::MUL:                return visitMUL(N);
   case ISD::SDIV:               return visitSDIV(N);
   case ISD::UDIV:               return visitUDIV(N);
   case ISD::SREM:
   case ISD::UREM:               return visitREM(N);
   case ISD::MULHU:              return visitMULHU(N);
   case ISD::MULHS:              return visitMULHS(N);
SDValue DAGCombiner::visitADDC(SDNode *N) {
   // If it cannot overflow, transform into an add.
   if (DAG.computeOverflowKind(N0, N1) == SelectionDAG::OFK_Never)
     return CombineTo(N, DAG.getNode(ISD::ADD, DL, VT, N0, N1),
                      DAG.getNode(ISD::CARRY_FALSE, DL, MVT::Glue));
 
   return SDValue();
 }
 
+SDValue DAGCombiner::visitUADDO(SDNode *N) {
+  SDValue N0 = N->getOperand(0);
+  SDValue N1 = N->getOperand(1);
+  EVT VT = N0.getValueType();
+  EVT CarryVT = N->getValueType(1);
+  SDLoc DL(N);
+
+  // If the flag result is dead, turn this into an ADD.
+  if (!N->hasAnyUseOfValue(1))
+    return CombineTo(N, DAG.getNode(ISD::ADD, DL, VT, N0, N1),
+                     DAG.getUNDEF(CarryVT));
+
+  // canonicalize constant to RHS.
+  ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0);
+  ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1);
+  if (N0C && !N1C)
+    return DAG.getNode(ISD::UADDO, DL, N->getVTList(), N1, N0);
+
+  // fold (uaddo x, 0) -> x + no carry out
+  if (isNullConstant(N1))
+    return CombineTo(N, N0, DAG.getConstant(0, DL, CarryVT));
+
+  // If it cannot overflow, transform into an add.
+  if (DAG.computeOverflowKind(N0, N1) == SelectionDAG::OFK_Never)
+    return CombineTo(N, DAG.getNode(ISD::ADD, DL, VT, N0, N1),
+                     DAG.getConstant(0, DL, CarryVT));
+
+  return SDValue();
+}
+
 SDValue DAGCombiner::visitADDE(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
   SDValue CarryIn = N->getOperand(2);
 
   // canonicalize constant to RHS
   ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0);
   ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1);
   if (N0C && !N1C)
     return DAG.getNode(ISD::ADDE, SDLoc(N), N->getVTList(),
                        N1, N0, CarryIn);
 
   // fold (adde x, y, false) -> (addc x, y)
   if (CarryIn.getOpcode() == ISD::CARRY_FALSE)
     return DAG.getNode(ISD::ADDC, SDLoc(N), N->getVTList(), N0, N1);
 
   return SDValue();
 }
 
+SDValue DAGCombiner::visitADDCARRY(SDNode *N) {
+  SDValue N0 = N->getOperand(0);
+  SDValue N1 = N->getOperand(1);
+  SDValue CarryIn = N->getOperand(2);
+
+  // canonicalize constant to RHS
+  ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0);
+  ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1);
+  if (N0C && !N1C)
+    return DAG.getNode(ISD::ADDCARRY, SDLoc(N), N->getVTList(),
+                       N1, N0, CarryIn);
+
+  // fold (addcarry x, y, false) -> (uaddo x, y)
+  if (isNullConstant(CarryIn))
+    return DAG.getNode(ISD::UADDO, SDLoc(N), N->getVTList(), N0, N1);
+
+  return SDValue();
+}
+
 // Since it may not be valid to emit a fold to zero for vector initializers
 // check if we can before folding.
 static SDValue tryFoldToZero(const SDLoc &DL, const TargetLowering &TLI, EVT VT,
                              SelectionDAG &DAG, bool LegalOperations,
                              bool LegalTypes) {
   if (!VT.isVector())
     return DAG.getConstant(0, DL, VT);
   if (!LegalOperations || TLI.isOperationLegal(ISD::BUILD_VECTOR, VT))
if (N0.getOpcode() == ISD::BITCAST && !VT.isVector()) {
     }
   }
 
   // Simplify the operands using demanded-bits information.
   if (!VT.isVector() &&
       SimplifyDemandedBits(SDValue(N, 0)))
     return SDValue(N, 0);
 
   // (trunc adde(X, Y, Carry)) -> (adde trunc(X), trunc(Y), Carry)
   // When the adde's carry is not used.
-  if (N0.getOpcode() == ISD::ADDE && N0.hasOneUse() &&
-      !N0.getNode()->hasAnyUseOfValue(1) &&
-      (!LegalOperations || TLI.isOperationLegal(ISD::ADDE, VT))) {
+  // Also works with addcarry.
+  if ((N0.getOpcode() == ISD::ADDE || N0.getOpcode() == ISD::ADDCARRY) &&
+      N0.hasOneUse() && !N0.getNode()->hasAnyUseOfValue(1) &&
+      (!LegalOperations || TLI.isOperationLegal(N0.getOpcode(), VT))) {
     SDLoc SL(N);
     auto X = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(0));
     auto Y = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(1));
-    return DAG.getNode(ISD::ADDE, SL, DAG.getVTList(VT, MVT::Glue),
-                       X, Y, N0.getOperand(2));
+    auto VTs = DAG.getVTList(VT, N0->getValueType(1));
+    return DAG.getNode(N0.getOpcode(), SL, VTs, X, Y, N0.getOperand(2));
   }
 
   return SDValue();
 }
 
 static SDNode *getBuildPairElt(SDNode *N, unsigned i) {
   SDValue Elt = N->getOperand(i);
   if (Elt.getOpcode() != ISD::MERGE_VALUES)

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

#endif
 
   case ISD::SADDO:
   case ISD::SSUBO:       Res = PromoteIntRes_SADDSUBO(N, ResNo); break;
   case ISD::UADDO:
   case ISD::USUBO:       Res = PromoteIntRes_UADDSUBO(N, ResNo); break;
   case ISD::SMULO:
   case ISD::UMULO:       Res = PromoteIntRes_XMULO(N, ResNo); break;
 
+  case ISD::ADDCARRY:
+  case ISD::SUBCARRY:    Res = PromoteIntRes_ADDSUBCARRY(N, ResNo); break;
+
   case ISD::ATOMIC_LOAD:
     Res = PromoteIntRes_Atomic0(cast<AtomicSDNode>(N)); break;
 
   case ISD::ATOMIC_LOAD_ADD:
   case ISD::ATOMIC_LOAD_SUB:
   case ISD::ATOMIC_LOAD_AND:
   case ISD::ATOMIC_LOAD_OR:
   case ISD::ATOMIC_LOAD_XOR:
SDValue DAGTypeLegalizer::PromoteIntRes_MGATHER(MaskedGatherSDNode *N) {
   return Res;
 }
 
 /// Promote the overflow flag of an overflowing arithmetic node.
 SDValue DAGTypeLegalizer::PromoteIntRes_Overflow(SDNode *N) {
   // Simply change the return type of the boolean result.
   EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(1));
   EVT ValueVTs[] = { N->getValueType(0), NVT };
-  SDValue Ops[] = { N->getOperand(0), N->getOperand(1) };
+  SDValue Ops[3] = { N->getOperand(0), N->getOperand(1) };
+  auto C = N->getNumOperands();
+  assert(C <= 3 && "Too many operands");
+  if (C == 3)
+    Ops[2] = N->getOperand(2);
+
   SDValue Res = DAG.getNode(N->getOpcode(), SDLoc(N),
-                            DAG.getVTList(ValueVTs), Ops);
+                            DAG.getVTList(ValueVTs), makeArrayRef(Ops, C));
 
   // Modified the sum result - switch anything that used the old sum to use
   // the new one.
   ReplaceValueWith(SDValue(N, 0), Res);
 
   return SDValue(Res.getNode(), 1);
 }
 
SDValue DAGTypeLegalizer::PromoteIntRes_UADDSUBO(SDNode *N, unsigned ResNo) {
   Ofl = DAG.getSetCC(dl, N->getValueType(1), Ofl, Res, ISD::SETNE);
 
   // Use the calculated overflow everywhere.
   ReplaceValueWith(SDValue(N, 1), Ofl);
 
   return Res;
 }
 
+SDValue DAGTypeLegalizer::PromoteIntRes_ADDSUBCARRY(SDNode *N, unsigned ResNo) {
+  if (ResNo == 1)
+    return PromoteIntRes_Overflow(N);
+  llvm_unreachable("Not implemented");
+}
+
 SDValue DAGTypeLegalizer::PromoteIntRes_XMULO(SDNode *N, unsigned ResNo) {
   // Promote the overflow bit trivially.
   if (ResNo == 1)
     return PromoteIntRes_Overflow(N);
 
   SDValue LHS = N->getOperand(0), RHS = N->getOperand(1);
   SDLoc DL(N);
   EVT SmallVT = LHS.getValueType();
bool DAGTypeLegalizer::PromoteIntegerOperand(SDNode *N, unsigned OpNo) {
   case ISD::ZERO_EXTEND:  Res = PromoteIntOp_ZERO_EXTEND(N); break;
   case ISD::EXTRACT_SUBVECTOR: Res = PromoteIntOp_EXTRACT_SUBVECTOR(N); break;
 
   case ISD::SHL:
   case ISD::SRA:
   case ISD::SRL:
   case ISD::ROTL:
   case ISD::ROTR: Res = PromoteIntOp_Shift(N); break;
+
+  case ISD::ADDCARRY:
+  case ISD::SUBCARRY: Res = PromoteIntOp_ADDSUBCARRY(N, OpNo); break;
   }
 
   // If the result is null, the sub-method took care of registering results etc.
   if (!Res.getNode()) return false;
 
   // If the result is N, the sub-method updated N in place.  Tell the legalizer
   // core about this.
   if (Res.getNode() == N)

 SDValue DAGTypeLegalizer::PromoteIntOp_ZERO_EXTEND(SDNode *N) {
   SDLoc dl(N);
   SDValue Op = GetPromotedInteger(N->getOperand(0));
   Op = DAG.getNode(ISD::ANY_EXTEND, dl, N->getValueType(0), Op);
   return DAG.getZeroExtendInReg(Op, dl,
                                 N->getOperand(0).getValueType().getScalarType());
 }
 
+SDValue DAGTypeLegalizer::PromoteIntOp_ADDSUBCARRY(SDNode *N, unsigned OpNo) {
+  assert(OpNo == 2 && "Don't know how to promote this operand!");
+
+  SDValue LHS = N->getOperand(0);
+  SDValue RHS = N->getOperand(1);
+  auto Carry = N->getOperand(2);
+  SDLoc DL(N);
+
+  auto VT = getSetCCResultType(LHS.getValueType());
+  TargetLoweringBase::BooleanContent BoolType = TLI.getBooleanContents(VT);
+  switch (BoolType) {
+  case TargetLoweringBase::UndefinedBooleanContent:
+    Carry = DAG.getAnyExtOrTrunc(Carry, DL, VT);
+    break;
+  case TargetLoweringBase::ZeroOrOneBooleanContent:
+    Carry = DAG.getZExtOrTrunc(Carry, DL, VT);
+    break;
+  case TargetLoweringBase::ZeroOrNegativeOneBooleanContent:
+    Carry = DAG.getSExtOrTrunc(Carry, DL, VT);
+    break;
+  }
+
+  return SDValue(DAG.UpdateNodeOperands(N, LHS, RHS, Carry), 0);
+}
 
 //===----------------------------------------------------------------------===//
 //  Integer Result Expansion
 //===----------------------------------------------------------------------===//
 
 /// ExpandIntegerResult - This method is called when the specified result of the
 /// specified node is found to need expansion.  At this point, the node may also
 /// have invalid operands or may have other results that need promotion, we just
#endif
   case ISD::SUB: ExpandIntRes_ADDSUB(N, Lo, Hi); break;
 
   case ISD::ADDC:
   case ISD::SUBC: ExpandIntRes_ADDSUBC(N, Lo, Hi); break;
 
   case ISD::ADDE:
   case ISD::SUBE: ExpandIntRes_ADDSUBE(N, Lo, Hi); break;
 
+  case ISD::ADDCARRY:
+  case ISD::SUBCARRY: ExpandIntRes_ADDSUBCARRY(N, Lo, Hi); break;
+
   case ISD::SHL:
   case ISD::SRA:
   case ISD::SRL: ExpandIntRes_Shift(N, Lo, Hi); break;
 
   case ISD::SADDO:
   case ISD::SSUBO: ExpandIntRes_SADDSUBO(N, Lo, Hi); break;
   case ISD::UADDO:
   case ISD::USUBO: ExpandIntRes_UADDSUBO(N, Lo, Hi); break;
void DAGTypeLegalizer::ExpandIntRes_ADDSUB(SDNode *N,
   SDValue LHSL, LHSH, RHSL, RHSH;
   GetExpandedInteger(N->getOperand(0), LHSL, LHSH);
   GetExpandedInteger(N->getOperand(1), RHSL, RHSH);
 
   EVT NVT = LHSL.getValueType();
   SDValue LoOps[2] = { LHSL, RHSL };
   SDValue HiOps[3] = { LHSH, RHSH };
 
+  bool hasOPCARRY =
+    TLI.isOperationLegalOrCustom(N->getOpcode() == ISD::ADD ?
+                                   ISD::ADDCARRY : ISD::SUBCARRY,
+                                 TLI.getTypeToExpandTo(*DAG.getContext(), NVT));
+  if (hasOPCARRY) {
+    SDVTList VTList = DAG.getVTList(NVT, getSetCCResultType(NVT));
+    if (N->getOpcode() == ISD::ADD) {
+      Lo = DAG.getNode(ISD::UADDO, dl, VTList, LoOps);
+      HiOps[2] = Lo.getValue(1);
+      Hi = DAG.getNode(ISD::ADDCARRY, dl, VTList, HiOps);
+    } else {
+      Lo = DAG.getNode(ISD::USUBO, dl, VTList, LoOps);
+      HiOps[2] = Lo.getValue(1);
+      Hi = DAG.getNode(ISD::SUBCARRY, dl, VTList, HiOps);
+    }
+    return;
+  }
+
   // Do not generate ADDC/ADDE or SUBC/SUBE if the target does not support
   // them.  TODO: Teach operation legalization how to expand unsupported
   // ADDC/ADDE/SUBC/SUBE.  The problem is that these operations generate
   // a carry of type MVT::Glue, but there doesn't seem to be any way to
   // generate a value of this type in the expanded code sequence.
   bool hasCarry =
     TLI.isOperationLegalOrCustom(N->getOpcode() == ISD::ADD ?
                                    ISD::ADDC : ISD::SUBC,
if (hasCarry) {
     return;
   }
 
   bool hasOVF =
     TLI.isOperationLegalOrCustom(N->getOpcode() == ISD::ADD ?
                                    ISD::UADDO : ISD::USUBO,
                                  TLI.getTypeToExpandTo(*DAG.getContext(), NVT));
   if (hasOVF) {
-    SDVTList VTList = DAG.getVTList(NVT, NVT);
+    EVT OvfVT = getSetCCResultType(NVT);
+    SDVTList VTList = DAG.getVTList(NVT, OvfVT);
     TargetLoweringBase::BooleanContent BoolType = TLI.getBooleanContents(NVT);
     int RevOpc;
     if (N->getOpcode() == ISD::ADD) {
       RevOpc = ISD::SUB;
       Lo = DAG.getNode(ISD::UADDO, dl, VTList, LoOps);
       Hi = DAG.getNode(ISD::ADD, dl, NVT, makeArrayRef(HiOps, 2));
     } else {
       RevOpc = ISD::ADD;
       Lo = DAG.getNode(ISD::USUBO, dl, VTList, LoOps);
       Hi = DAG.getNode(ISD::SUB, dl, NVT, makeArrayRef(HiOps, 2));
     }
     SDValue OVF = Lo.getValue(1);
 
     switch (BoolType) {
     case TargetLoweringBase::UndefinedBooleanContent:
-      OVF = DAG.getNode(ISD::AND, dl, NVT, DAG.getConstant(1, dl, NVT), OVF);
+      OVF = DAG.getNode(ISD::AND, dl, OvfVT, DAG.getConstant(1, dl, OvfVT), OVF);
       LLVM_FALLTHROUGH;
     case TargetLoweringBase::ZeroOrOneBooleanContent:
+      OVF = DAG.getZExtOrTrunc(OVF, dl, NVT);
       Hi = DAG.getNode(N->getOpcode(), dl, NVT, Hi, OVF);
       break;
     case TargetLoweringBase::ZeroOrNegativeOneBooleanContent:
+      OVF = DAG.getSExtOrTrunc(OVF, dl, NVT);
       Hi = DAG.getNode(RevOpc, dl, NVT, Hi, OVF);
     }
     return;
   }
 
   if (N->getOpcode() == ISD::ADD) {
     Lo = DAG.getNode(ISD::ADD, dl, NVT, LoOps);
     Hi = DAG.getNode(ISD::ADD, dl, NVT, makeArrayRef(HiOps, 2));
void DAGTypeLegalizer::ExpandIntRes_ADDSUBE(SDNode *N,
   HiOps[2] = Lo.getValue(1);
   Hi = DAG.getNode(N->getOpcode(), dl, VTList, HiOps);
 
   // Legalized the flag result - switch anything that used the old flag to
   // use the new one.
   ReplaceValueWith(SDValue(N, 1), Hi.getValue(1));
 }
 
+void DAGTypeLegalizer::ExpandIntRes_UADDSUBO(SDNode *N,
+                                             SDValue &Lo, SDValue &Hi) {
+  SDValue LHS = N->getOperand(0);
+  SDValue RHS = N->getOperand(1);
+  SDLoc dl(N);
+
+  SDValue Ovf;
+
+  bool hasOPCARRY =
+    TLI.isOperationLegalOrCustom(N->getOpcode() == ISD::ADD ?
+                                 ISD::ADDCARRY : ISD::SUBCARRY,
+                                 TLI.getTypeToExpandTo(*DAG.getContext(),
+                                                       LHS.getValueType()));
+
+  if (hasOPCARRY) {
+    // Expand the subcomponents.
+    SDValue LHSL, LHSH, RHSL, RHSH;
+    GetExpandedInteger(LHS, LHSL, LHSH);
+    GetExpandedInteger(RHS, RHSL, RHSH);
+    SDVTList VTList = DAG.getVTList(LHSL.getValueType(), N->getValueType(1));
+    SDValue LoOps[2] = { LHSL, RHSL };
+    SDValue HiOps[3] = { LHSH, RHSH };
+
+    auto Opc = N->getOpcode() == ISD::UADDO ? ISD::ADDCARRY : ISD::SUBCARRY;
+    Lo = DAG.getNode(N->getOpcode(), dl, VTList, LoOps);
+    HiOps[2] = Lo.getValue(1);
+    Hi = DAG.getNode(Opc, dl, VTList, HiOps);
+
+    Ovf = Hi.getValue(1);
+  } else {
+    // Expand the result by simply replacing it with the equivalent
+    // non-overflow-checking operation.
+    auto Opc = N->getOpcode() == ISD::UADDO ? ISD::ADD : ISD::SUB;
+    SDValue Sum = DAG.getNode(Opc, dl, LHS.getValueType(), LHS, RHS);
+    SplitInteger(Sum, Lo, Hi);
+
+    // Calculate the overflow: addition overflows iff a + b < a, and subtraction
+    // overflows iff a - b > a.
+    auto Cond = N->getOpcode() == ISD::UADDO ? ISD::SETULT : ISD::SETUGT;
+    Ovf = DAG.getSetCC(dl, N->getValueType(1), Sum, LHS, Cond);
+  }
+
+  // Legalized the flag result - switch anything that used the old flag to
+  // use the new one.
+  ReplaceValueWith(SDValue(N, 1), Ovf);
+}
+
+void DAGTypeLegalizer::ExpandIntRes_ADDSUBCARRY(SDNode *N,
+                                                SDValue &Lo, SDValue &Hi) {
+  // Expand the subcomponents.
+  SDValue LHSL, LHSH, RHSL, RHSH;
+  SDLoc dl(N);
+  GetExpandedInteger(N->getOperand(0), LHSL, LHSH);
+  GetExpandedInteger(N->getOperand(1), RHSL, RHSH);
+  SDVTList VTList = DAG.getVTList(LHSL.getValueType(), N->getValueType(1));
+  SDValue LoOps[3] = { LHSL, RHSL, N->getOperand(2) };
+  SDValue HiOps[3] = { LHSH, RHSH };
+
+  Lo = DAG.getNode(N->getOpcode(), dl, VTList, LoOps);
+  HiOps[2] = Lo.getValue(1);
+  Hi = DAG.getNode(N->getOpcode(), dl, VTList, HiOps);
+
+  // Legalized the flag result - switch anything that used the old flag to
+  // use the new one.
+  ReplaceValueWith(SDValue(N, 1), Hi.getValue(1));
+}
+
 void DAGTypeLegalizer::ExpandIntRes_ANY_EXTEND(SDNode *N,
                                                SDValue &Lo, SDValue &Hi) {
   EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0));
   SDLoc dl(N);
   SDValue Op = N->getOperand(0);
   if (Op.getValueType().bitsLE(NVT)) {
     // The low part is any extension of the input (which degenerates to a copy).
     Lo = DAG.getNode(ISD::ANY_EXTEND, dl, NVT, Op);
void DAGTypeLegalizer::ExpandIntRes_TRUNCATE(SDNode *N,
   Lo = DAG.getNode(ISD::TRUNCATE, dl, NVT, N->getOperand(0));
   Hi = DAG.getNode(ISD::SRL, dl, N->getOperand(0).getValueType(),
                    N->getOperand(0),
                    DAG.getConstant(NVT.getSizeInBits(), dl,
                                    TLI.getPointerTy(DAG.getDataLayout())));
   Hi = DAG.getNode(ISD::TRUNCATE, dl, NVT, Hi);
 }
 
-void DAGTypeLegalizer::ExpandIntRes_UADDSUBO(SDNode *N,
-                                             SDValue &Lo, SDValue &Hi) {
-  SDValue LHS = N->getOperand(0);
-  SDValue RHS = N->getOperand(1);
-  SDLoc dl(N);
-
-  // Expand the result by simply replacing it with the equivalent
-  // non-overflow-checking operation.
-  SDValue Sum = DAG.getNode(N->getOpcode() == ISD::UADDO ?
-                            ISD::ADD : ISD::SUB, dl, LHS.getValueType(),
-                            LHS, RHS);
-  SplitInteger(Sum, Lo, Hi);
-
-  // Calculate the overflow: addition overflows iff a + b < a, and subtraction
-  // overflows iff a - b > a.
-  SDValue Ofl = DAG.getSetCC(dl, N->getValueType(1), Sum, LHS,
-                             N->getOpcode () == ISD::UADDO ?
-                             ISD::SETULT : ISD::SETUGT);
-
-  // Use the calculated overflow everywhere.
-  ReplaceValueWith(SDValue(N, 1), Ofl);
-}
-
 void DAGTypeLegalizer::ExpandIntRes_XMULO(SDNode *N,
                                           SDValue &Lo, SDValue &Hi) {
   EVT VT = N->getValueType(0);
   SDLoc dl(N);
 
   // A divide for UMULO should be faster than a function call.
   if (N->getOpcode() == ISD::UMULO) {
     SDValue LHS = N->getOperand(0), RHS = N->getOperand(1);

lib/CodeGen/SelectionDAG/LegalizeTypes.h

private:
   SDValue PromoteIntRes_SimpleIntBinOp(SDNode *N);
   SDValue PromoteIntRes_ZExtIntBinOp(SDNode *N);
   SDValue PromoteIntRes_SExtIntBinOp(SDNode *N);
   SDValue PromoteIntRes_SIGN_EXTEND_INREG(SDNode *N);
   SDValue PromoteIntRes_SRA(SDNode *N);
   SDValue PromoteIntRes_SRL(SDNode *N);
   SDValue PromoteIntRes_TRUNCATE(SDNode *N);
   SDValue PromoteIntRes_UADDSUBO(SDNode *N, unsigned ResNo);
+  SDValue PromoteIntRes_ADDSUBCARRY(SDNode *N, unsigned ResNo);
   SDValue PromoteIntRes_UNDEF(SDNode *N);
   SDValue PromoteIntRes_VAARG(SDNode *N);
   SDValue PromoteIntRes_XMULO(SDNode *N, unsigned ResNo);
 
   // Integer Operand Promotion.
   bool PromoteIntegerOperand(SDNode *N, unsigned OperandNo);
   SDValue PromoteIntOp_ANY_EXTEND(SDNode *N);
   SDValue PromoteIntOp_ATOMIC_STORE(AtomicSDNode *N);
private:
   SDValue PromoteIntOp_STORE(StoreSDNode *N, unsigned OpNo);
   SDValue PromoteIntOp_TRUNCATE(SDNode *N);
   SDValue PromoteIntOp_UINT_TO_FP(SDNode *N);
   SDValue PromoteIntOp_ZERO_EXTEND(SDNode *N);
   SDValue PromoteIntOp_MSTORE(MaskedStoreSDNode *N, unsigned OpNo);
   SDValue PromoteIntOp_MLOAD(MaskedLoadSDNode *N, unsigned OpNo);
   SDValue PromoteIntOp_MSCATTER(MaskedScatterSDNode *N, unsigned OpNo);
   SDValue PromoteIntOp_MGATHER(MaskedGatherSDNode *N, unsigned OpNo);
+  SDValue PromoteIntOp_ADDSUBCARRY(SDNode *N, unsigned OpNo);
 
   void PromoteSetCCOperands(SDValue &LHS,SDValue &RHS, ISD::CondCode Code);
 
   //===--------------------------------------------------------------------===//
   // Integer Expansion Support: LegalizeIntegerTypes.cpp
   //===--------------------------------------------------------------------===//
 
   /// Given a processed operand Op which was expanded into two integers of half
private:
   void ExpandIntRes_FLT_ROUNDS        (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_FP_TO_SINT        (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_FP_TO_UINT        (SDNode *N, SDValue &Lo, SDValue &Hi);
 
   void ExpandIntRes_Logical           (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_ADDSUB            (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_ADDSUBC           (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_ADDSUBE           (SDNode *N, SDValue &Lo, SDValue &Hi);
+  void ExpandIntRes_ADDSUBCARRY       (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_BITREVERSE        (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_BSWAP             (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_MUL               (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_SDIV              (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_SREM              (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_UDIV              (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_UREM              (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_Shift             (SDNode *N, SDValue &Lo, SDValue &Hi);

lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp

#endif
   case ISD::CONCAT_VECTORS:             return "concat_vectors";
   case ISD::INSERT_SUBVECTOR:           return "insert_subvector";
   case ISD::EXTRACT_SUBVECTOR:          return "extract_subvector";
   case ISD::SCALAR_TO_VECTOR:           return "scalar_to_vector";
   case ISD::VECTOR_SHUFFLE:             return "vector_shuffle";
   case ISD::CARRY_FALSE:                return "carry_false";
   case ISD::ADDC:                       return "addc";
   case ISD::ADDE:                       return "adde";
+  case ISD::ADDCARRY:                   return "addcarry";
   case ISD::SADDO:                      return "saddo";
   case ISD::UADDO:                      return "uaddo";
   case ISD::SSUBO:                      return "ssubo";
   case ISD::USUBO:                      return "usubo";
   case ISD::SMULO:                      return "smulo";
   case ISD::UMULO:                      return "umulo";
   case ISD::SUBC:                       return "subc";
   case ISD::SUBE:                       return "sube";
+  case ISD::SUBCARRY:                   return "subcarry";
   case ISD::SHL_PARTS:                  return "shl_parts";
   case ISD::SRA_PARTS:                  return "sra_parts";
   case ISD::SRL_PARTS:                  return "srl_parts";
 
   // Conversion operators.
   case ISD::SIGN_EXTEND:                return "sign_extend";
   case ISD::ZERO_EXTEND:                return "zero_extend";
   case ISD::ANY_EXTEND:                 return "any_extend";

lib/CodeGen/TargetLoweringBase.cpp

for (MVT VT : MVT::all_valuetypes()) {
     // Overflow operations default to expand
     setOperationAction(ISD::SADDO, VT, Expand);
     setOperationAction(ISD::SSUBO, VT, Expand);
     setOperationAction(ISD::UADDO, VT, Expand);
     setOperationAction(ISD::USUBO, VT, Expand);
     setOperationAction(ISD::SMULO, VT, Expand);
     setOperationAction(ISD::UMULO, VT, Expand);
 
+    // ADDCARRY and SUBCARRY are new additions which needs
+    // to default to expand to not break all backends.
+    setOperationAction(ISD::ADDCARRY, VT, Expand);
+    setOperationAction(ISD::SUBCARRY, VT, Expand);
+
     // These default to Expand so they will be expanded to CTLZ/CTTZ by default.
     setOperationAction(ISD::CTLZ_ZERO_UNDEF, VT, Expand);
     setOperationAction(ISD::CTTZ_ZERO_UNDEF, VT, Expand);
 
     setOperationAction(ISD::BITREVERSE, VT, Expand);
     
     // These library functions default to expand.
     setOperationAction(ISD::FROUND, VT, Expand);

lib/Target/X86/X86ISelDAGToDAG.cpp

if (U == Root) {
     case X86ISD::ADD:
     case X86ISD::SUB:
     case X86ISD::AND:
     case X86ISD::XOR:
     case X86ISD::OR:
     case ISD::ADD:
     case ISD::ADDC:
     case ISD::ADDE:
+    case ISD::ADDCARRY:
     case ISD::AND:
     case ISD::OR:
     case ISD::XOR: {
       SDValue Op1 = U->getOperand(1);
 
       // If the other operand is a 8-bit immediate we should fold the immediate
       // instead. This reduces code size.
       // e.g.

lib/Target/X86/X86ISelLowering.cpp

if (VT == MVT::i64 && !Subtarget.is64Bit())
       continue;
     // Add/Sub/Mul with overflow operations are custom lowered.
     setOperationAction(ISD::SADDO, VT, Custom);
     setOperationAction(ISD::UADDO, VT, Custom);
     setOperationAction(ISD::SSUBO, VT, Custom);
     setOperationAction(ISD::USUBO, VT, Custom);
     setOperationAction(ISD::SMULO, VT, Custom);
     setOperationAction(ISD::UMULO, VT, Custom);
+
+    // Support carry in as value rather than glue.
+    setOperationAction(ISD::ADDCARRY, VT, Custom);
+    setOperationAction(ISD::SUBCARRY, VT, Custom);
   }
 
   if (!Subtarget.is64Bit()) {
     // These libcalls are not available in 32-bit.
     setLibcallName(RTLIB::SHL_I128, nullptr);
     setLibcallName(RTLIB::SRL_I128, nullptr);
     setLibcallName(RTLIB::SRA_I128, nullptr);
   }
static SDValue LowerADDC_ADDE_SUBC_SUBE(SDValue Op, SelectionDAG &DAG) {
 
   if (!ExtraOp)
     return DAG.getNode(Opc, SDLoc(Op), VTs, Op.getOperand(0),
                        Op.getOperand(1));
   return DAG.getNode(Opc, SDLoc(Op), VTs, Op.getOperand(0),
                      Op.getOperand(1), Op.getOperand(2));
 }
 
+static SDValue LowerADDSUBCARRY(SDValue Op, SelectionDAG &DAG) {
+  auto N = Op.getNode();
+  MVT VT = N->getSimpleValueType(0);
+
+  // Let legalize expand this if it isn't a legal type yet.
+  if (!DAG.getTargetLoweringInfo().isTypeLegal(VT))
+    return SDValue();
+
+  SDVTList VTs = DAG.getVTList(VT, MVT::i32);
+  SDLoc DL(N);
+
+  // Set the carry flag.
+  SDValue Carry = Op.getOperand(2);
+  EVT CarryVT = Carry.getValueType();
+  APInt NegOne = APInt::getAllOnesValue(CarryVT.getScalarSizeInBits());
+  Carry = DAG.getNode(X86ISD::ADD, DL, DAG.getVTList(CarryVT, MVT::i32),
+                      Carry, DAG.getConstant(NegOne, DL, CarryVT));
+
+  unsigned Opc = Op.getOpcode() == ISD::ADDCARRY ? X86ISD::ADC : X86ISD::SBB;
+  auto Sum = DAG.getNode(Opc, DL, VTs, Op.getOperand(0),
+                         Op.getOperand(1), Carry.getValue(1));
+
+  SDValue SetCC = getSETCC(X86::COND_B, Sum.getValue(1), DL, DAG);
+  if (N->getValueType(1) == MVT::i1)
+    SetCC = DAG.getNode(ISD::TRUNCATE, DL, MVT::i1, SetCC);
+
+  return DAG.getNode(ISD::MERGE_VALUES, DL, N->getVTList(), Sum, SetCC);
+}
+
 static SDValue LowerFSINCOS(SDValue Op, const X86Subtarget &Subtarget,
                             SelectionDAG &DAG) {
   assert(Subtarget.isTargetDarwin() && Subtarget.is64Bit());
 
   // For MacOSX, we want to call an alternative entry point: __sincos_stret,
   // which returns the values as { float, float } (in XMM0) or
   // { double, double } (which is returned in XMM0, XMM1).
   SDLoc dl(Op);
SDValue X86TargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   case ISD::SMULO:
   case ISD::UMULO:              return LowerXALUO(Op, DAG);
   case ISD::READCYCLECOUNTER:   return LowerREADCYCLECOUNTER(Op, Subtarget,DAG);
   case ISD::BITCAST:            return LowerBITCAST(Op, Subtarget, DAG);
   case ISD::ADDC:
   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::ADD:
   case ISD::SUB:                return LowerADD_SUB(Op, DAG);
   case ISD::SMAX:
   case ISD::SMIN:
   case ISD::UMAX:
   case ISD::UMIN:               return LowerMINMAX(Op, DAG);
   case ISD::FSINCOS:            return LowerFSINCOS(Op, Subtarget, DAG);
   case ISD::MLOAD:              return LowerMLOAD(Op, Subtarget, DAG);
if (!Ld->isVolatile() && !VT.isVector() &&
           SDValue(N, 0), LdVT, Ld->getChain(), Op0, DAG);
       DAG.ReplaceAllUsesOfValueWith(Op0.getValue(1), FILDChain.getValue(1));
       return FILDChain;
     }
   }
   return SDValue();
 }
 
+// Optimize RES, EFLAGS = X86ISD::ADD LHS, RHS
+static SDValue combineADD(SDNode *N, SelectionDAG &DAG,
+                          X86TargetLowering::DAGCombinerInfo &DCI) {
+  // When legalizing carry, we create carries via add X, -1
+  // If that comes from an actual carry, via setcc, we use the
+  // carry directly.
+  if (isAllOnesConstant(N->getOperand(1)) && N->hasAnyUseOfValue(1)) {
+    auto Carry = N->getOperand(0);
+    while (Carry.getOpcode() == ISD::TRUNCATE ||
+           Carry.getOpcode() == ISD::ZERO_EXTEND ||
+           Carry.getOpcode() == ISD::SIGN_EXTEND ||
+           Carry.getOpcode() == ISD::ANY_EXTEND ||
+           (Carry.getOpcode() == ISD::AND &&
+            isOneConstant(Carry.getOperand(1))))
+      Carry = Carry.getOperand(0);
+
+    if (Carry.getOpcode() == ISD::SETCC ||
+        Carry.getOpcode() == X86ISD::SETCC_CARRY) {
+      auto Cond = cast<ConstantSDNode>(Carry.getOperand(0));
+      if (Cond->getZExtValue() == X86::COND_B) {
+        return DCI.CombineTo(N, SDValue(N, 0), Carry.getOperand(1));
+      }
+    }
+  }
+
+  return SDValue();
+}
+
 // Optimize RES, EFLAGS = X86ISD::ADC LHS, RHS, EFLAGS
 static SDValue combineADC(SDNode *N, SelectionDAG &DAG,
                           X86TargetLowering::DAGCombinerInfo &DCI) {
   // If the LHS and RHS of the ADC node are zero, then it can't overflow and
   // the result is either zero or one (depending on the input carry bit).
   // Strength reduce this down to a "set on carry" aka SETCC_CARRY&1.
   if (X86::isZeroNode(N->getOperand(0)) &&
       X86::isZeroNode(N->getOperand(1)) &&
case ISD::INSERT_SUBVECTOR:
     return combineInsertSubvector(N, DAG, DCI, Subtarget);
   case ISD::VSELECT:
   case ISD::SELECT:
   case X86ISD::SHRUNKBLEND: return combineSelect(N, DAG, DCI, Subtarget);
   case ISD::BITCAST:        return combineBitcast(N, DAG, Subtarget);
   case X86ISD::CMOV:        return combineCMov(N, DAG, DCI, Subtarget);
   case ISD::ADD:            return combineAdd(N, DAG, Subtarget);
   case ISD::SUB:            return combineSub(N, DAG, Subtarget);
+  case X86ISD::ADD:         return combineADD(N, DAG, DCI);
   case X86ISD::ADC:         return combineADC(N, DAG, DCI);
   case ISD::MUL:            return combineMul(N, DAG, DCI, Subtarget);
   case ISD::SHL:
   case ISD::SRA:
   case ISD::SRL:            return combineShift(N, DAG, DCI, Subtarget);
   case ISD::AND:            return combineAnd(N, DAG, DCI, Subtarget);
   case ISD::OR:             return combineOr(N, DAG, DCI, Subtarget);
   case ISD::XOR:            return combineXor(N, DAG, DCI, Subtarget);

test/CodeGen/Generic/icmp-illegal.ll

-
 ; RUN: llc < %s | FileCheck %s
 
 ; CHECK-LABEL: test_ult
 define i1 @test_ult(i256 %a) nounwind {
   %1 = icmp ult i256 %a, -6432394258550908438
   ret i1 %1
 }
 

test/CodeGen/X86/known-bits.ll

 ; X32-NEXT:    movl {{[0-9]+}}(%esp), %edi
 ; X32-NEXT:    andl %esi, %edi
 ; X32-NEXT:    andl {{[0-9]+}}(%esp), %esi
 ; X32-NEXT:    addl %edi, %esi
 ; X32-NEXT:    adcl {{[0-9]+}}(%esp), %edx
 ; X32-NEXT:    adcl $0, %ecx
 ; X32-NEXT:    shldl $22, %edx, %ecx
 ; X32-NEXT:    shldl $22, %esi, %edx
+; X32-NEXT:    shll $22, %esi
+; X32-NEXT:    movl %esi, 4(%eax)
 ; X32-NEXT:    movl %edx, 8(%eax)
 ; X32-NEXT:    movl %ecx, 12(%eax)
-; X32-NEXT:    movl $0, 4(%eax)
 ; X32-NEXT:    movl $0, (%eax)
 ; X32-NEXT:    popl %esi
 ; X32-NEXT:    popl %edi
 ; X32-NEXT:    retl $4
 ;
 ; X64-LABEL: knownbits_mask_addc_shl:
 ; X64:       # BB#0:
 ; X64-NEXT:    andq $-1024, %rdi # imm = 0xFC00
 ; X64-NEXT:    andq $-1024, %rsi # imm = 0xFC00
 ; X64-NEXT:    addq %rdi, %rsi
 ; X64-NEXT:    adcl $0, %edx
 ; X64-NEXT:    shldq $54, %rsi, %rdx
-; X64-NEXT:    xorl %eax, %eax
+; X64-NEXT:    shlq $54, %rsi
+; X64-NEXT:    movq %rsi, %rax
 ; X64-NEXT:    retq
   %1 = and i64 %a0, -1024
   %2 = zext i64 %1 to i128
   %3 = and i64 %a1, -1024
   %4 = zext i64 %3 to i128
   %5 = add i128 %2, %4
   %6 = zext i64 %a2 to i128
   %7 = shl i128 %6, 64
   %8 = add i128 %5, %7
   %9 = shl i128 %8, 54
   ret i128 %9
 }