Do not legalize large setcc with setcce, introduce setcccarry and do it with usubo/setcccarry.

Summary:
This is a continuation of the work started in D29872 . Passing the carry down as a value rather than as a glue allows for further optimizations. Introducing setcccarry makes the use of addc/subc unecessary and we can start the removal process.

This patch only introduce the optimization strictly required to get the same level of optimization as was available before nothing more.

Reviewers: jyknight, nemanjai, mkuper, spatel, RKSimon, zvi, bkramer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33374

llvm-svn: 304404

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 9d77d75ae00..2298eb096da 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -1578,6 +1578,7 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     // Support carry in as value rather than glue.
     setOperationAction(ISD::ADDCARRY, VT, Custom);
     setOperationAction(ISD::SUBCARRY, VT, Custom);
+    setOperationAction(ISD::SETCCCARRY, VT, Custom);
   }
 
   if (!Subtarget.is64Bit()) {
@@ -17413,6 +17414,30 @@ SDValue X86TargetLowering::LowerSETCCE(SDValue Op, SelectionDAG &DAG) const {
   return SetCC;
 }
 
+SDValue X86TargetLowering::LowerSETCCCARRY(SDValue Op, SelectionDAG &DAG) const {
+  SDValue LHS = Op.getOperand(0);
+  SDValue RHS = Op.getOperand(1);
+  SDValue Carry = Op.getOperand(2);
+  SDValue Cond = Op.getOperand(3);
+  SDLoc DL(Op);
+
+  assert(LHS.getSimpleValueType().isInteger() && "SETCCCARRY is integer only.");
+  X86::CondCode CC = TranslateIntegerX86CC(cast<CondCodeSDNode>(Cond)->get());
+
+  // Recreate the carry if needed.
+  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));
+
+  SDVTList VTs = DAG.getVTList(LHS.getValueType(), MVT::i32);
+  SDValue Cmp = DAG.getNode(X86ISD::SBB, DL, VTs, LHS, RHS, Carry.getValue(1));
+  SDValue SetCC = getSETCC(CC, Cmp.getValue(1), DL, DAG);
+  if (Op.getSimpleValueType() == MVT::i1)
+    return DAG.getNode(ISD::TRUNCATE, DL, MVT::i1, SetCC);
+  return SetCC;
+}
+
 /// Return true if opcode is a X86 logical comparison.
 static bool isX86LogicalCmp(SDValue Op) {
   unsigned Opc = Op.getOpcode();
@@ -23782,6 +23807,7 @@ SDValue X86TargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   case ISD::FGETSIGN:           return LowerFGETSIGN(Op, DAG);
   case ISD::SETCC:              return LowerSETCC(Op, DAG);
   case ISD::SETCCE:             return LowerSETCCE(Op, DAG);
+  case ISD::SETCCCARRY:         return LowerSETCCCARRY(Op, DAG);
   case ISD::SELECT:             return LowerSELECT(Op, DAG);
   case ISD::BRCOND:             return LowerBRCOND(Op, DAG);
   case ISD::JumpTable:          return LowerJumpTable(Op, DAG);