diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp index b94febf786e..5d7624c1ebc 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp @@ -73,11 +73,12 @@ reassociateShiftAmtsOfTwoSameDirectionShifts(BinaryOperator *Sh0, // a) (x & ((1 << MaskShAmt) - 1)) << ShiftShAmt // b) (x & (~(-1 << MaskShAmt))) << ShiftShAmt // c) (x & (-1 >> MaskShAmt)) << ShiftShAmt +// d) (x & ((-1 << MaskShAmt) >> MaskShAmt)) << ShiftShAmt // All these patterns can be simplified to just: // x << ShiftShAmt // iff: // a,b) (MaskShAmt+ShiftShAmt) u>= bitwidth(x) -// c) (ShiftShAmt-MaskShAmt) s>= 0 (i.e. ShiftShAmt u>= MaskShAmt) +// c,d) (ShiftShAmt-MaskShAmt) s>= 0 (i.e. ShiftShAmt u>= MaskShAmt) static Instruction * dropRedundantMaskingOfLeftShiftInput(BinaryOperator *OuterShift, const SimplifyQuery &SQ) { @@ -95,6 +96,9 @@ dropRedundantMaskingOfLeftShiftInput(BinaryOperator *OuterShift, auto MaskB = m_Xor(m_Shl(m_AllOnes(), m_Value(MaskShAmt)), m_AllOnes()); // (-1 >> MaskShAmt) auto MaskC = m_Shr(m_AllOnes(), m_Value(MaskShAmt)); + // ((-1 << MaskShAmt) >> MaskShAmt) + auto MaskD = + m_Shr(m_Shl(m_AllOnes(), m_Value(MaskShAmt)), m_Deferred(MaskShAmt)); Value *X; if (match(Masked, m_c_And(m_CombineOr(MaskA, MaskB), m_Value(X)))) { @@ -111,7 +115,7 @@ dropRedundantMaskingOfLeftShiftInput(BinaryOperator *OuterShift, APInt(BitWidth, BitWidth)))) return nullptr; // All good, we can do this fold. - } else if (match(Masked, m_c_And(MaskC, m_Value(X)))) { + } else if (match(Masked, m_c_And(m_CombineOr(MaskC, MaskD), m_Value(X)))) { // Can we simplify (ShiftShAmt-MaskShAmt) ? Value *ShAmtsDiff = SimplifySubInst(ShiftShAmt, MaskShAmt, /*IsNSW=*/false, /*IsNUW=*/false, |
