[llvm] 684cbae - [KnownBits] Introduce `countMaxActiveBits()` and use it in a few places

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2021-10-11T23:36:06+03:00
New Revision: 684cbae89a78f4329a018237ec6f230a82dbc883

URL: https://github.com/llvm/llvm-project/commit/684cbae89a78f4329a018237ec6f230a82dbc883
DIFF: https://github.com/llvm/llvm-project/commit/684cbae89a78f4329a018237ec6f230a82dbc883.diff

LOG: [KnownBits] Introduce `countMaxActiveBits()` and use it in a few places

Added: 
    

Modified: 
    llvm/include/llvm/Support/KnownBits.h
    llvm/lib/Analysis/InstructionSimplify.cpp
    llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
    llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
    llvm/unittests/Support/KnownBitsTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Support/KnownBits.h b/llvm/include/llvm/Support/KnownBits.h
index 556f8e872ed6b..1f32760a6fd1b 100644
--- a/llvm/include/llvm/Support/KnownBits.h
+++ b/llvm/include/llvm/Support/KnownBits.h
@@ -282,6 +282,10 @@ struct KnownBits {
     return getBitWidth() - Zero.countPopulation();
   }
 
+  unsigned countMaxActiveBits() const {
+    return getBitWidth() - countMinLeadingZeros();
+  }
+
   /// Create known bits from a known constant.
   static KnownBits makeConstant(const APInt &C) {
     return KnownBits(~C, C);

diff  --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 97cb0c9c86c02..04948d2ecbf1c 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1407,8 +1407,7 @@ static Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
       match(Op0, m_c_Or(m_NUWShl(m_Value(X), m_APInt(ShLAmt)), m_Value(Y))) &&
       *ShRAmt == *ShLAmt) {
     const KnownBits YKnown = computeKnownBits(Y, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
-    const unsigned Width = Op0->getType()->getScalarSizeInBits();
-    const unsigned EffWidthY = Width - YKnown.countMinLeadingZeros();
+    const unsigned EffWidthY = YKnown.countMaxActiveBits();
     if (ShRAmt->uge(EffWidthY))
       return X;
   }
@@ -2159,11 +2158,11 @@ static Value *SimplifyAndInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
     const unsigned Width = Op0->getType()->getScalarSizeInBits();
     const unsigned ShftCnt = ShAmt->getLimitedValue(Width);
     const KnownBits YKnown = computeKnownBits(Y, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
-    const unsigned EffWidthY = Width - YKnown.countMinLeadingZeros();
+    const unsigned EffWidthY = YKnown.countMaxActiveBits();
     if (EffWidthY <= ShftCnt) {
       const KnownBits XKnown = computeKnownBits(X, Q.DL, 0, Q.AC, Q.CxtI,
                                                 Q.DT);
-      const unsigned EffWidthX = Width - XKnown.countMinLeadingZeros();
+      const unsigned EffWidthX = XKnown.countMaxActiveBits();
       const APInt EffBitsY = APInt::getLowBitsSet(Width, EffWidthY);
       const APInt EffBitsX = APInt::getLowBitsSet(Width, EffWidthX) << ShftCnt;
       // If the mask is extracting all bits from X or Y as is, we can skip

diff  --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
index ec666a15abd33..2b8ff6afac568 100644
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -2210,7 +2210,7 @@ bool CombinerHelper::matchCombineTruncOfShl(
            {DstTy, getTargetLowering().getPreferredShiftAmountTy(DstTy)}})) {
     KnownBits Known = KB->getKnownBits(ShiftAmt);
     unsigned Size = DstTy.getSizeInBits();
-    if (Known.getBitWidth() - Known.countMinLeadingZeros() <= Log2_32(Size)) {
+    if (Known.countMaxActiveBits() <= Log2_32(Size)) {
       MatchInfo = std::make_pair(ShiftSrc, ShiftAmt);
       return true;
     }

diff  --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 550c6bcb8d65e..7272ac9d9b403 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -12305,7 +12305,7 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
     SDValue Amt = N0.getOperand(1);
     KnownBits Known = DAG.computeKnownBits(Amt);
     unsigned Size = VT.getScalarSizeInBits();
-    if (Known.getBitWidth() - Known.countMinLeadingZeros() <= Log2_32(Size)) {
+    if (Known.countMaxActiveBits() <= Log2_32(Size)) {
       SDLoc SL(N);
       EVT AmtVT = TLI.getShiftAmountTy(VT, DAG.getDataLayout());
 

diff  --git a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
index 269c33e30bfc4..49abb1e008900 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -45,9 +45,7 @@ EVT AMDGPUTargetLowering::getEquivalentMemType(LLVMContext &Ctx, EVT VT) {
 }
 
 unsigned AMDGPUTargetLowering::numBitsUnsigned(SDValue Op, SelectionDAG &DAG) {
-  EVT VT = Op.getValueType();
-  KnownBits Known = DAG.computeKnownBits(Op);
-  return VT.getSizeInBits() - Known.countMinLeadingZeros();
+  return DAG.computeKnownBits(Op).countMaxActiveBits();
 }
 
 unsigned AMDGPUTargetLowering::numBitsSigned(SDValue Op, SelectionDAG &DAG) {
@@ -3360,7 +3358,7 @@ SDValue AMDGPUTargetLowering::performTruncateCombine(
       KnownBits Known = DAG.computeKnownBits(Amt);
       unsigned Size = VT.getScalarSizeInBits();
       if ((Known.isConstant() && Known.getConstant().ule(Size)) ||
-          (Known.getBitWidth() - Known.countMinLeadingZeros() <= Log2_32(Size))) {
+          (Known.countMaxActiveBits() <= Log2_32(Size))) {
         EVT MidVT = VT.isVector() ?
           EVT::getVectorVT(*DAG.getContext(), MVT::i32,
                            VT.getVectorNumElements()) : MVT::i32;

diff  --git a/llvm/unittests/Support/KnownBitsTest.cpp b/llvm/unittests/Support/KnownBitsTest.cpp
index c38f99a3f9539..f9631f29902f5 100644
--- a/llvm/unittests/Support/KnownBitsTest.cpp
+++ b/llvm/unittests/Support/KnownBitsTest.cpp
@@ -431,6 +431,17 @@ TEST(KnownBitsTest, GetSignedMinMaxVal) {
   });
 }
 
+TEST(KnownBitsTest, CountMaxActiveBits) {
+  unsigned Bits = 4;
+  ForeachKnownBits(Bits, [&](const KnownBits &Known) {
+    unsigned Expected = 0;
+    ForeachNumInKnownBits(Known, [&](const APInt &N) {
+      Expected = std::max(Expected, N.getActiveBits());
+    });
+    EXPECT_EQ(Expected, Known.countMaxActiveBits());
+  });
+}
+
 TEST(KnownBitsTest, SExtOrTrunc) {
   const unsigned NarrowerSize = 4;
   const unsigned BaseSize = 6;