[llvm] [AArch64] SimplifyDemandedBitsForTargetNode - add AArch64ISD::BICi handling (PR #76644)

[Sizov Nikita via llvm-commits]

https://github.com/snikitav updated https://github.com/llvm/llvm-project/pull/76644

>From c155e8ffdb2b3d563713213f74fec5909069041b Mon Sep 17 00:00:00 2001
From: Sizov Nikita <s.nikita.v at gmail.com>
Date: Sun, 31 Dec 2023 04:33:21 +0300
Subject: [PATCH] Missing AArch64ISD::BICi handling

---
 .../Target/AArch64/AArch64ISelLowering.cpp    | 31 +++++++++++++++++++
 .../AArch64/aarch64-known-bits-hadd.ll        |  4 ---
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index f552f91929201c..6fb3ad7a8d2e02 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -24580,6 +24580,19 @@ 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:
@@ -27620,6 +27633,24 @@ 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 = KnownOp0 &
+            KnownBits::makeConstant(APInt(Known.getBitWidth(), ~BitsToClear));
+
+    return false;
+  }
   case ISD::INTRINSIC_WO_CHAIN: {
     if (auto ElementSize = IsSVECntIntrinsic(Op)) {
       unsigned MaxSVEVectorSizeInBits = Subtarget->getMaxSVEVectorSizeInBits();
diff --git a/llvm/test/CodeGen/AArch64/aarch64-known-bits-hadd.ll b/llvm/test/CodeGen/AArch64/aarch64-known-bits-hadd.ll
index 017f382774892c..f36b8440fe4bfb 100644
--- a/llvm/test/CodeGen/AArch64/aarch64-known-bits-hadd.ll
+++ b/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>