diff options
Diffstat (limited to 'llvm/lib/Analysis/ValueTracking.cpp')
| -rw-r--r-- | llvm/lib/Analysis/ValueTracking.cpp | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index ed3fa35..52d3468 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -1426,16 +1426,23 @@ static void computeKnownBitsFromOperator(const Operator *I, // this is sufficient to catch some interesting cases. unsigned Opcode = BO->getOpcode(); - // If this is a shift recurrence, we know the bits being shifted in. - // We can combine that with information about the start value of the - // recurrence to conclude facts about the result. switch (Opcode) { + // If this is a shift recurrence, we know the bits being shifted in. We + // can combine that with information about the start value of the + // recurrence to conclude facts about the result. If this is a udiv + // recurrence, we know that the result can never exceed either the + // numerator or the start value, whichever is greater. case Instruction::LShr: case Instruction::AShr: - case Instruction::Shl: { + case Instruction::Shl: + case Instruction::UDiv: if (BO->getOperand(0) != I) break; + [[fallthrough]]; + // For a urem recurrence, the result can never exceed the start value. The + // phi could either be the numerator or the denominator. + case Instruction::URem: { // We have matched a recurrence of the form: // %iv = [R, %entry], [%iv.next, %backedge] // %iv.next = shift_op %iv, L @@ -1453,8 +1460,10 @@ static void computeKnownBitsFromOperator(const Operator *I, Known.Zero.setLowBits(Known2.countMinTrailingZeros()); break; case Instruction::LShr: - // A lshr recurrence will preserve the leading zeros of the - // start value + case Instruction::UDiv: + case Instruction::URem: + // lshr, udiv, and urem recurrences will preserve the leading zeros of + // the start value. Known.Zero.setHighBits(Known2.countMinLeadingZeros()); break; case Instruction::AShr: @@ -1542,6 +1551,7 @@ static void computeKnownBitsFromOperator(const Operator *I, } break; } + default: break; } @@ -9039,12 +9049,14 @@ bool llvm::matchSimpleRecurrence(const PHINode *P, BinaryOperator *&BO, switch (Opcode) { default: continue; - // TODO: Expand list -- xor, div, gep, uaddo, etc.. + // TODO: Expand list -- xor, gep, uadd.sat etc. case Instruction::LShr: case Instruction::AShr: case Instruction::Shl: case Instruction::Add: case Instruction::Sub: + case Instruction::UDiv: + case Instruction::URem: case Instruction::And: case Instruction::Or: case Instruction::Mul: |