Missing AArch64ISD::BICi handling

Author: snikitav

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -3416,13 +3416,18 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
       Known = KnownBits::mulhs(Known, Known2);
     break;
   }
-  case ISD::AVGCEILU: {
+  case ISD::AVGFLOORU:
+  case ISD::AVGCEILU:
+  case ISD::AVGFLOORS:
+  case ISD::AVGCEILS: {
+    bool IsCeil = Opcode == ISD::AVGCEILU || Opcode == ISD::AVGCEILS;
+    bool IsSigned = Opcode == ISD::AVGFLOORS || Opcode == ISD::AVGCEILS;
     Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
     Known2 = computeKnownBits(Op.getOperand(1), DemandedElts, Depth + 1);
-    Known = Known.zext(BitWidth + 1);
-    Known2 = Known2.zext(BitWidth + 1);
-    KnownBits One = KnownBits::makeConstant(APInt(1, 1));
-    Known = KnownBits::computeForAddCarry(Known, Known2, One);
+    Known = IsSigned ? Known.sext(BitWidth + 1) : Known.zext(BitWidth + 1);
+    Known2 = IsSigned ? Known2.sext(BitWidth + 1) : Known2.zext(BitWidth + 1);
+    KnownBits Carry = KnownBits::makeConstant(APInt(1, IsCeil ? 1 : 0));
+    Known = KnownBits::computeForAddCarry(Known, Known2, Carry);
     Known = Known.extractBits(BitWidth, 1);
     break;
   }

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -24486,6 +24486,19 @@ SDValue AArch64TargetLowering::PerformDAGCombine(SDNode *N,
     if (auto R = foldOverflowCheck(N, DAG, /* IsAdd */ false))
       return R;
     return performFlagSettingCombine(N, DCI, AArch64ISD::SBC);
+  case AArch64ISD::BICi: {
+    KnownBits Known;
+    APInt DemandedBits =
+        APInt::getAllOnes(N->getValueType(0).getScalarSizeInBits());
+    APInt DemandedElts =
+        APInt::getAllOnes(N->getValueType(0).getVectorNumElements());
+    TargetLowering::TargetLoweringOpt TLO(DAG, !DCI.isBeforeLegalize(),
+                                          !DCI.isBeforeLegalizeOps());
+    if (DAG.getTargetLoweringInfo().SimplifyDemandedBits(
+            SDValue(N, 0), DemandedBits, DemandedElts, Known, TLO))
+      return TLO.New;
+    break;
+  }
   case ISD::XOR:
     return performXorCombine(N, DAG, DCI, Subtarget);
   case ISD::MUL:
@@ -27526,6 +27539,23 @@ bool AArch64TargetLowering::SimplifyDemandedBitsForTargetNode(
     // used - simplify to just Val.
     return TLO.CombineTo(Op, ShiftR->getOperand(0));
   }
+  case AArch64ISD::BICi: {
+    // Fold BICi if all destination bits already known to be zeroed
+    SDValue Op0 = Op.getOperand(0);
+    KnownBits KnownOp0 =
+        TLO.DAG.computeKnownBits(Op0, OriginalDemandedElts, Depth + 1);
+    // Op0 &= ~(ConstantOperandVal(1) << ConstantOperandVal(2))
+    uint64_t BitsToClear = Op->getConstantOperandVal(1)
+                           << Op->getConstantOperandVal(2);
+    APInt AlreadyZeroedBitsToClear = BitsToClear & KnownOp0.Zero;
+    if (APInt(Known.getBitWidth(), BitsToClear)
+            .isSubsetOf(AlreadyZeroedBitsToClear))
+      return TLO.CombineTo(Op, Op0);
+
+    Known &= KnownBits::makeConstant(APInt(Known.getBitWidth(), ~BitsToClear));
+
+    return false;
+  }
   case ISD::INTRINSIC_WO_CHAIN: {
     if (auto ElementSize = IsSVECntIntrinsic(Op)) {
       unsigned MaxSVEVectorSizeInBits = Subtarget->getMaxSVEVectorSizeInBits();

llvm/test/CodeGen/AArch64/aarch64-known-bits-hadd.ll

@@ -12,7 +12,6 @@ define <8 x i16> @haddu_zext(<8 x i8> %a0, <8 x i8> %a1) {
 ; CHECK-NEXT:    ushll v0.8h, v0.8b, #0
 ; CHECK-NEXT:    ushll v1.8h, v1.8b, #0
 ; CHECK-NEXT:    uhadd v0.8h, v0.8h, v1.8h
-; CHECK-NEXT:    bic v0.8h, #254, lsl #8
 ; CHECK-NEXT:    ret
   %x0 = zext <8 x i8> %a0 to <8 x i16>
   %x1 = zext <8 x i8> %a1 to <8 x i16>
@@ -27,7 +26,6 @@ define <8 x i16> @rhaddu_zext(<8 x i8> %a0, <8 x i8> %a1) {
 ; CHECK-NEXT:    ushll v0.8h, v0.8b, #0
 ; CHECK-NEXT:    ushll v1.8h, v1.8b, #0
 ; CHECK-NEXT:    urhadd v0.8h, v0.8h, v1.8h
-; CHECK-NEXT:    bic v0.8h, #254, lsl #8
 ; CHECK-NEXT:    ret
   %x0 = zext <8 x i8> %a0 to <8 x i16>
   %x1 = zext <8 x i8> %a1 to <8 x i16>
@@ -42,7 +40,6 @@ define <8 x i16> @hadds_zext(<8 x i8> %a0, <8 x i8> %a1) {
 ; CHECK-NEXT:    ushll v0.8h, v0.8b, #0
 ; CHECK-NEXT:    ushll v1.8h, v1.8b, #0
 ; CHECK-NEXT:    shadd v0.8h, v0.8h, v1.8h
-; CHECK-NEXT:    bic v0.8h, #254, lsl #8
 ; CHECK-NEXT:    ret
   %x0 = zext <8 x i8> %a0 to <8 x i16>
   %x1 = zext <8 x i8> %a1 to <8 x i16>
@@ -57,7 +54,6 @@ define <8 x i16> @shaddu_zext(<8 x i8> %a0, <8 x i8> %a1) {
 ; CHECK-NEXT:    ushll v0.8h, v0.8b, #0
 ; CHECK-NEXT:    ushll v1.8h, v1.8b, #0
 ; CHECK-NEXT:    srhadd v0.8h, v0.8h, v1.8h
-; CHECK-NEXT:    bic v0.8h, #254, lsl #8
 ; CHECK-NEXT:    ret
   %x0 = zext <8 x i8> %a0 to <8 x i16>
   %x1 = zext <8 x i8> %a1 to <8 x i16>

llvm/unittests/CodeGen/AArch64SelectionDAGTest.cpp

@@ -9,6 +9,7 @@
 #include "llvm/Analysis/MemoryLocation.h"
 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
 #include "llvm/AsmParser/Parser.h"
+#include "llvm/CodeGen/ISDOpcodes.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/SelectionDAG.h"
 #include "llvm/CodeGen/TargetLowering.h"
@@ -796,4 +797,52 @@ TEST_F(AArch64SelectionDAGTest, computeKnownBits_extload_knownnegative) {
   EXPECT_EQ(Known.One, APInt(32, 0xfffffff0));
 }
 
+TEST_F(AArch64SelectionDAGTest,
+       computeKnownBits_AVGFLOORU_AVGFLOORS_AVGCEILU_AVGCEILS) {
+  SDLoc Loc;
+  auto Int8VT = EVT::getIntegerVT(Context, 8);
+  auto Int16VT = EVT::getIntegerVT(Context, 16);
+  auto Int8Vec8VT = EVT::getVectorVT(Context, Int8VT, 8);
+  auto Int16Vec8VT = EVT::getVectorVT(Context, Int16VT, 8);
+
+  SDValue UnknownOp0 = DAG->getRegister(0, Int8Vec8VT);
+  SDValue UnknownOp1 = DAG->getRegister(1, Int8Vec8VT);
+
+  SDValue ZextOp0 =
+      DAG->getNode(ISD::ZERO_EXTEND, Loc, Int16Vec8VT, UnknownOp0);
+  SDValue ZextOp1 =
+      DAG->getNode(ISD::ZERO_EXTEND, Loc, Int16Vec8VT, UnknownOp1);
+  // ZextOp0 = 00000000????????
+  // ZextOp1 = 00000000????????
+  // => (for all AVG* instructions)
+  // Known.Zero = 1111111100000000 (0xFF00)
+  // Known.One  = 0000000000000000 (0x0000)
+  auto Zeroes = APInt(16, 0xFF00);
+  auto Ones = APInt(16, 0x0000);
+
+  SDValue AVGFLOORU =
+      DAG->getNode(ISD::AVGFLOORU, Loc, Int16Vec8VT, ZextOp0, ZextOp1);
+  KnownBits KnownAVGFLOORU = DAG->computeKnownBits(AVGFLOORU);
+  EXPECT_EQ(KnownAVGFLOORU.Zero, Zeroes);
+  EXPECT_EQ(KnownAVGFLOORU.One, Ones);
+
+  SDValue AVGFLOORS =
+      DAG->getNode(ISD::AVGFLOORU, Loc, Int16Vec8VT, ZextOp0, ZextOp1);
+  KnownBits KnownAVGFLOORS = DAG->computeKnownBits(AVGFLOORS);
+  EXPECT_EQ(KnownAVGFLOORS.Zero, Zeroes);
+  EXPECT_EQ(KnownAVGFLOORS.One, Ones);
+
+  SDValue AVGCEILU =
+      DAG->getNode(ISD::AVGCEILU, Loc, Int16Vec8VT, ZextOp0, ZextOp1);
+  KnownBits KnownAVGCEILU = DAG->computeKnownBits(AVGCEILU);
+  EXPECT_EQ(KnownAVGCEILU.Zero, Zeroes);
+  EXPECT_EQ(KnownAVGCEILU.One, Ones);
+
+  SDValue AVGCEILS =
+      DAG->getNode(ISD::AVGCEILS, Loc, Int16Vec8VT, ZextOp0, ZextOp1);
+  KnownBits KnownAVGCEILS = DAG->computeKnownBits(AVGCEILS);
+  EXPECT_EQ(KnownAVGCEILS.Zero, Zeroes);
+  EXPECT_EQ(KnownAVGCEILS.One, Ones);
+}
+
 } // end namespace llvm