For Thumb1, lower ADDC/ADDE/SUBC/SUBE via the glueless ARMISD nodes,

same as already done for ARM and Thumb2.

Reviewers: jmolloy, rogfer01, efriedma

Subscribers: aemerson, llvm-commits, rengolin

Differential Revision: https://reviews.llvm.org/D30400

llvm-svn: 297443

1 files changed, 63 insertions, 12 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 6d735a3bed0..e7cfbba98b1 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -826,13 +826,10 @@ ARMTargetLowering::ARMTargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::SRL,       MVT::i64, Custom);
   setOperationAction(ISD::SRA,       MVT::i64, Custom);
 
-  if (!Subtarget->isThumb1Only()) {
-    // FIXME: We should do this for Thumb1 as well.
-    setOperationAction(ISD::ADDC,    MVT::i32, Custom);
-    setOperationAction(ISD::ADDE,    MVT::i32, Custom);
-    setOperationAction(ISD::SUBC,    MVT::i32, Custom);
-    setOperationAction(ISD::SUBE,    MVT::i32, Custom);
-  }
+  setOperationAction(ISD::ADDC,      MVT::i32, Custom);
+  setOperationAction(ISD::ADDE,      MVT::i32, Custom);
+  setOperationAction(ISD::SUBC,      MVT::i32, Custom);
+  setOperationAction(ISD::SUBE,      MVT::i32, Custom);
 
   if (!Subtarget->isThumb1Only() && Subtarget->hasV6T2Ops())
     setOperationAction(ISD::BITREVERSE, MVT::i32, Legal);
@@ -9059,19 +9056,45 @@ void ARMTargetLowering::AdjustInstrPostInstrSelection(MachineInstr &MI,
 
   // Rename pseudo opcodes.
   unsigned NewOpc = convertAddSubFlagsOpcode(MI.getOpcode());
+  unsigned ccOutIdx;
   if (NewOpc) {
     const ARMBaseInstrInfo *TII = Subtarget->getInstrInfo();
     MCID = &TII->get(NewOpc);
 
-    assert(MCID->getNumOperands() == MI.getDesc().getNumOperands() + 1 &&
-           "converted opcode should be the same except for cc_out");
+    assert(MCID->getNumOperands() ==
+           MI.getDesc().getNumOperands() + 5 - MI.getDesc().getSize()
+        && "converted opcode should be the same except for cc_out"
+           " (and, on Thumb1, pred)");
 
     MI.setDesc(*MCID);
 
     // Add the optional cc_out operand
     MI.addOperand(MachineOperand::CreateReg(0, /*isDef=*/true));
-  }
-  unsigned ccOutIdx = MCID->getNumOperands() - 1;
+
+    // On Thumb1, move all input operands to the end, then add the predicate
+    if (Subtarget->isThumb1Only()) {
+      for (unsigned c = MCID->getNumOperands() - 4; c--;) {
+        MI.addOperand(MI.getOperand(1));
+        MI.RemoveOperand(1);
+      }
+
+      // Restore the ties
+      for (unsigned i = MI.getNumOperands(); i--;) {
+        const MachineOperand& op = MI.getOperand(i);
+        if (op.isReg() && op.isUse()) {
+          int DefIdx = MCID->getOperandConstraint(i, MCOI::TIED_TO);
+          if (DefIdx != -1)
+            MI.tieOperands(DefIdx, i);
+        }
+      }
+
+      MI.addOperand(MachineOperand::CreateImm(ARMCC::AL));
+      MI.addOperand(MachineOperand::CreateReg(0, /*isDef=*/false));
+      ccOutIdx = 1;
+    } else
+      ccOutIdx = MCID->getNumOperands() - 1;
+  } else
+    ccOutIdx = MCID->getNumOperands() - 1;
 
   // Any ARM instruction that sets the 's' bit should specify an optional
   // "cc_out" operand in the last operand position.
@@ -9102,7 +9125,9 @@ void ARMTargetLowering::AdjustInstrPostInstrSelection(MachineInstr &MI,
   if (deadCPSR) {
     assert(!MI.getOperand(ccOutIdx).getReg() &&
            "expect uninitialized optional cc_out operand");
-    return;
+    // Thumb1 instructions must have the S bit even if the CPSR is dead.
+    if (!Subtarget->isThumb1Only())
+      return;
   }
 
   // If this instruction was defined with an optional CPSR def and its dag node
@@ -9649,6 +9674,30 @@ static SDValue AddCombineTo64bitUMAAL(SDNode *AddcNode,
   return SDValue();
 }
 
+static SDValue PerformAddeSubeCombine(SDNode *N, SelectionDAG &DAG,
+                                      const ARMSubtarget *Subtarget) {
+  if (Subtarget->isThumb1Only()) {
+    SDValue RHS = N->getOperand(1);
+    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(RHS)) {
+      int64_t imm = C->getSExtValue();
+      if (imm < 0) {
+        SDLoc DL(N);
+
+        // The with-carry-in form matches bitwise not instead of the negation.
+        // Effectively, the inverse interpretation of the carry flag already
+        // accounts for part of the negation.
+        RHS = DAG.getConstant(~imm, DL, MVT::i32);
+
+        unsigned Opcode = (N->getOpcode() == ARMISD::ADDE) ? ARMISD::SUBE
+                                                           : ARMISD::ADDE;
+        return DAG.getNode(Opcode, DL, N->getVTList(),
+                           N->getOperand(0), RHS, N->getOperand(2));
+      }
+    }
+  }
+  return SDValue();
+}
+
 /// PerformADDCCombine - Target-specific dag combine transform from
 /// ISD::ADDC, ISD::ADDE, and ISD::MUL_LOHI to MLAL or
 /// ISD::ADDC, ISD::ADDE and ARMISD::UMLAL to ARMISD::UMAAL
@@ -11691,6 +11740,8 @@ SDValue ARMTargetLowering::PerformDAGCombine(SDNode *N,
   case ISD::OR:         return PerformORCombine(N, DCI, Subtarget);
   case ISD::XOR:        return PerformXORCombine(N, DCI, Subtarget);
   case ISD::AND:        return PerformANDCombine(N, DCI, Subtarget);
+  case ARMISD::ADDE:
+  case ARMISD::SUBE:    return PerformAddeSubeCombine(N, DCI.DAG, Subtarget);
   case ARMISD::BFI:     return PerformBFICombine(N, DCI);
   case ARMISD::VMOVRRD: return PerformVMOVRRDCombine(N, DCI, Subtarget);
   case ARMISD::VMOVDRR: return PerformVMOVDRRCombine(N, DCI.DAG);