[llvm] 11c1065 - [ValueTracking] Update computeKnownBitsFromShiftOperator callbacks to use KnownBits shift handling. NFCI.

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2020-11-12T15:31:26Z
New Revision: 11c106544bca50fcb6eaa768513a7e9c3e135a41

URL: https://github.com/llvm/llvm-project/commit/11c106544bca50fcb6eaa768513a7e9c3e135a41
DIFF: https://github.com/llvm/llvm-project/commit/11c106544bca50fcb6eaa768513a7e9c3e135a41.diff

LOG: [ValueTracking] Update computeKnownBitsFromShiftOperator callbacks to use KnownBits shift handling. NFCI.

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp

Removed: 
    


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diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index b740b148a681..a7aee656a290 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1221,14 +1221,13 @@ static void computeKnownBitsFromOperator(const Operator *I,
     break;
   }
   case Instruction::Shl: {
-    // (shl X, C1) & C2 == 0   iff   (X & C2 >>u C1) == 0
     bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
     auto KF = [NSW](const KnownBits &KnownShiftVal, unsigned ShiftAmt) {
-      KnownBits Result;
-      Result.Zero = KnownShiftVal.Zero << ShiftAmt;
-      Result.One = KnownShiftVal.One << ShiftAmt;
-      // Low bits known zero.
-      Result.Zero.setLowBits(ShiftAmt);
+      APInt ShiftAmtV(KnownShiftVal.getBitWidth(), ShiftAmt);
+      KnownBits KnownShiftAmt;
+      KnownShiftAmt.One = ShiftAmtV;
+      KnownShiftAmt.Zero = ~ShiftAmtV;
+      KnownBits Result = KnownBits::shl(KnownShiftVal, KnownShiftAmt);
       // If this shift has "nsw" keyword, then the result is either a poison
       // value or has the same sign bit as the first operand.
       if (NSW) {
@@ -1244,26 +1243,24 @@ static void computeKnownBitsFromOperator(const Operator *I,
     break;
   }
   case Instruction::LShr: {
-    // (lshr X, C1) & C2 == 0   iff  (-1 >> C1) & C2 == 0
     auto KF = [](const KnownBits &KnownShiftVal, unsigned ShiftAmt) {
-      KnownBits Result;
-      Result.Zero = KnownShiftVal.Zero.lshr(ShiftAmt);
-      Result.One = KnownShiftVal.One.lshr(ShiftAmt);
-      // High bits known zero.
-      Result.Zero.setHighBits(ShiftAmt);
-      return Result;
+      APInt ShiftAmtV(KnownShiftVal.getBitWidth(), ShiftAmt);
+      KnownBits KnownShiftAmt;
+      KnownShiftAmt.One = ShiftAmtV;
+      KnownShiftAmt.Zero = ~ShiftAmtV;
+      return KnownBits::lshr(KnownShiftVal, KnownShiftAmt);
     };
     computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
                                       KF);
     break;
   }
   case Instruction::AShr: {
-    // (ashr X, C1) & C2 == 0   iff  (-1 >> C1) & C2 == 0
     auto KF = [](const KnownBits &KnownShiftVal, unsigned ShiftAmt) {
-      KnownBits Result;
-      Result.Zero = KnownShiftVal.Zero.ashr(ShiftAmt);
-      Result.One = KnownShiftVal.One.ashr(ShiftAmt);
-      return Result;
+      APInt ShiftAmtV(KnownShiftVal.getBitWidth(), ShiftAmt);
+      KnownBits KnownShiftAmt;
+      KnownShiftAmt.One = ShiftAmtV;
+      KnownShiftAmt.Zero = ~ShiftAmtV;
+      return KnownBits::ashr(KnownShiftVal, KnownShiftAmt);
     };
     computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
                                       KF);