[ADT] Add APInt::isNegatedPowerOf2() helper

Inspired by D111968, provide a isNegatedPowerOf2() wrapper instead of obfuscating code with (-Value).isPowerOf2() patterns, which I'm sure are likely avenues for typos.....

Differential Revision: https://reviews.llvm.org/D111998

diff --git a/llvm/include/llvm/ADT/APInt.h b/llvm/include/llvm/ADT/APInt.h
index 2b25806..71d75db 100644 (file)
--- a/llvm/include/llvm/ADT/APInt.h
+++ b/llvm/include/llvm/ADT/APInt.h
@@ -430,6 +430,17 @@ public:
     return countPopulationSlowCase() == 1;
   }
 
+  /// Check if this APInt's negated value is a power of two greater than zero.
+  bool isNegatedPowerOf2() const {
+    assert(BitWidth && "zero width values not allowed");
+    if (isNonNegative())
+      return false;
+    // NegatedPowerOf2 - shifted mask in the top bits.
+    unsigned LO = countLeadingOnes();
+    unsigned TZ = countTrailingZeros();
+    return (LO + TZ) == BitWidth;
+  }
+
   /// Check if the APInt's value is returned by getSignMask.
   ///
   /// \returns true if this is the value returned by getSignMask.

diff --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h
index fb5736f..6096cbd 100644 (file)
--- a/llvm/include/llvm/IR/PatternMatch.h
+++ b/llvm/include/llvm/IR/PatternMatch.h
@@ -549,7 +549,7 @@ inline api_pred_ty<is_power2> m_Power2(const APInt *&V) {
 }
 
 struct is_negated_power2 {
-  bool isValue(const APInt &C) { return (-C).isPowerOf2(); }
+  bool isValue(const APInt &C) { return C.isNegatedPowerOf2(); }
 };
 /// Match a integer or vector negated power-of-2.
 /// For vectors, this includes constants with undefined elements.

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a98a01c..5f656ec 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3841,7 +3841,7 @@ SDValue DAGCombiner::visitMUL(SDNode *N) {
   }
 
   // fold (mul x, -(1 << c)) -> -(x << c) or (-x) << c
-  if (N1IsConst && !N1IsOpaqueConst && (-ConstValue1).isPowerOf2()) {
+  if (N1IsConst && !N1IsOpaqueConst && ConstValue1.isNegatedPowerOf2()) {
     unsigned Log2Val = (-ConstValue1).logBase2();
     SDLoc DL(N);
     // FIXME: If the input is something that is easily negated (e.g. a
@@ -4212,7 +4212,7 @@ SDValue DAGCombiner::visitSDIVLike(SDValue N0, SDValue N1, SDNode *N) {
       return false;
     if (C->getAPIntValue().isPowerOf2())
       return true;
-    if ((-C->getAPIntValue()).isPowerOf2())
+    if (C->getAPIntValue().isNegatedPowerOf2())
       return true;
     return false;
   };

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index cc2b96f..fa1c3cf 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -4150,7 +4150,7 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
           N0.getOpcode() == ISD::AND && N0.hasOneUse()) {
         if (auto *AndRHS = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
           const APInt &AndRHSC = AndRHS->getAPIntValue();
-          if ((-AndRHSC).isPowerOf2() && (AndRHSC & C1) == C1) {
+          if (AndRHSC.isNegatedPowerOf2() && (AndRHSC & C1) == C1) {
             unsigned ShiftBits = AndRHSC.countTrailingZeros();
             if (!TLI.shouldAvoidTransformToShift(ShValTy, ShiftBits)) {
               SDValue Shift =

diff --git a/llvm/lib/Target/AArch64/AArch64FastISel.cpp b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
index 066e198..3dc694d 100644 (file)
--- a/llvm/lib/Target/AArch64/AArch64FastISel.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
@@ -4806,7 +4806,7 @@ bool AArch64FastISel::selectSDiv(const Instruction *I) {
 
   const APInt &C = cast<ConstantInt>(I->getOperand(1))->getValue();
   if ((VT != MVT::i32 && VT != MVT::i64) || !C ||
-      !(C.isPowerOf2() || (-C).isPowerOf2()))
+      !(C.isPowerOf2() || C.isNegatedPowerOf2()))
     return selectBinaryOp(I, ISD::SDIV);
 
   unsigned Lg2 = C.countTrailingZeros();

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index f63e4cf..560effa 100644 (file)
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -12802,7 +12802,7 @@ AArch64TargetLowering::BuildSDIVPow2(SDNode *N, const APInt &Divisor,
   // fold (sdiv X, pow2)
   EVT VT = N->getValueType(0);
   if ((VT != MVT::i32 && VT != MVT::i64) ||
-      !(Divisor.isPowerOf2() || (-Divisor).isPowerOf2()))
+      !(Divisor.isPowerOf2() || Divisor.isNegatedPowerOf2()))
     return SDValue();
 
   SDLoc DL(N);

diff --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
index d8bb593..88de84a 100644 (file)
--- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -342,7 +342,7 @@ static bool isSSATMinMaxPattern(Instruction *Inst, const APInt &Imm) {
 
   if (InstSPF == SPF_SMAX &&
       PatternMatch::match(RHS, PatternMatch::m_ConstantInt(C)) &&
-      C->getValue() == Imm && Imm.isNegative() && (-Imm).isPowerOf2()) {
+      C->getValue() == Imm && Imm.isNegative() && Imm.isNegatedPowerOf2()) {
 
     auto isSSatMin = [&](Value *MinInst) {
       if (isa<SelectInst>(MinInst)) {

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index b8fda71..36d0841 100644 (file)
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -15606,13 +15606,13 @@ PPCTargetLowering::BuildSDIVPow2(SDNode *N, const APInt &Divisor,
   if (VT == MVT::i64 && !Subtarget.isPPC64())
     return SDValue();
   if ((VT != MVT::i32 && VT != MVT::i64) ||
-      !(Divisor.isPowerOf2() || (-Divisor).isPowerOf2()))
+      !(Divisor.isPowerOf2() || Divisor.isNegatedPowerOf2()))
     return SDValue();
 
   SDLoc DL(N);
   SDValue N0 = N->getOperand(0);
 
-  bool IsNegPow2 = (-Divisor).isPowerOf2();
+  bool IsNegPow2 = Divisor.isNegatedPowerOf2();
   unsigned Lg2 = (IsNegPow2 ? -Divisor : Divisor).countTrailingZeros();
   SDValue ShiftAmt = DAG.getConstant(Lg2, DL, VT);
 

diff --git a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
index 4310e4a..6d66ebf 100644 (file)
--- a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
@@ -424,8 +424,8 @@ InstructionCost SystemZTTIImpl::getArithmeticInstrCost(
           (C->getType()->isVectorTy()
                ? dyn_cast_or_null<const ConstantInt>(C->getSplatValue())
                : dyn_cast<const ConstantInt>(C));
-      if (CVal != nullptr &&
-          (CVal->getValue().isPowerOf2() || (-CVal->getValue()).isPowerOf2()))
+      if (CVal && (CVal->getValue().isPowerOf2() ||
+                   CVal->getValue().isNegatedPowerOf2()))
         DivRemConstPow2 = true;
       else
         DivRemConst = true;

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 85ff029..c435510 100644 (file)
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -23263,7 +23263,7 @@ X86TargetLowering::BuildSDIVPow2(SDNode *N, const APInt &Divisor,
   if (isIntDivCheap(N->getValueType(0), Attr))
     return SDValue(N,0); // Lower SDIV as SDIV
 
-  assert((Divisor.isPowerOf2() || (-Divisor).isPowerOf2()) &&
+  assert((Divisor.isPowerOf2() || Divisor.isNegatedPowerOf2()) &&
          "Unexpected divisor!");
 
   // Only perform this transform if CMOV is supported otherwise the select

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 4e05819..481f4dd 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1889,7 +1889,7 @@ Instruction *InstCombinerImpl::foldICmpAndConstant(ICmpInst &Cmp,
   // X & -C == -C -> X >  u ~C
   // X & -C != -C -> X <= u ~C
   //   iff C is a power of 2
-  if (Cmp.getOperand(1) == Y && (-C).isPowerOf2()) {
+  if (Cmp.getOperand(1) == Y && C.isNegatedPowerOf2()) {
     auto NewPred =
         Pred == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGT : CmpInst::ICMP_ULE;
     return new ICmpInst(NewPred, X, SubOne(cast<Constant>(Cmp.getOperand(1))));

diff --git a/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
index 84c3d1b..b473788 100644 (file)
--- a/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
@@ -620,7 +620,7 @@ Value *StraightLineStrengthReduce::emitBump(const Candidate &Basis,
     ConstantInt *Exponent = ConstantInt::get(DeltaType, IndexOffset.logBase2());
     return Builder.CreateShl(ExtendedStride, Exponent);
   }
-  if ((-IndexOffset).isPowerOf2()) {
+  if (IndexOffset.isNegatedPowerOf2()) {
     // If (i - i') is a power of 2, Bump = -sext/trunc(S) << log(i' - i).
     ConstantInt *Exponent =
         ConstantInt::get(DeltaType, (-IndexOffset).logBase2());

diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index 0efe28f..8a73163 100644 (file)
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -1785,6 +1785,32 @@ TEST(APIntTest, isPowerOf2) {
   }
 }
 
+TEST(APIntTest, isNegatedPowerOf2) {
+  EXPECT_FALSE(APInt(5, 0x00).isNegatedPowerOf2());
+  EXPECT_TRUE(APInt(15, 0x7ffe).isNegatedPowerOf2());
+  EXPECT_TRUE(APInt(16, 0xfffc).isNegatedPowerOf2());
+  EXPECT_TRUE(APInt(32, 0xffffffff).isNegatedPowerOf2());
+
+  for (int N : {1, 2, 3, 4, 7, 8, 16, 32, 64, 127, 128, 129, 256}) {
+    EXPECT_FALSE(APInt(N, 0).isNegatedPowerOf2());
+    EXPECT_TRUE(APInt::getAllOnes(N).isNegatedPowerOf2());
+    EXPECT_TRUE(APInt::getSignedMinValue(N).isNegatedPowerOf2());
+    EXPECT_TRUE((-APInt::getSignedMinValue(N)).isNegatedPowerOf2());
+
+    APInt One(N, 1);
+    for (int I = 1; I < N - 1; ++I) {
+      EXPECT_FALSE(APInt::getOneBitSet(N, I).isNegatedPowerOf2());
+      EXPECT_TRUE((-APInt::getOneBitSet(N, I)).isNegatedPowerOf2());
+
+      APInt MaskVal = One.shl(I);
+      EXPECT_TRUE((-MaskVal).isNegatedPowerOf2());
+
+      APInt ShiftMaskVal = One.getHighBitsSet(N, I);
+      EXPECT_TRUE(ShiftMaskVal.isNegatedPowerOf2());
+    }
+  }
+}
+
 // Test that self-move works with EXPENSIVE_CHECKS. It calls std::shuffle which
 // does self-move on some platforms.
 #ifdef EXPENSIVE_CHECKS