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[InstCombine] Handle commuted pattern for ((X s/ C1) << C2) + X #121737

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Merged
merged 4 commits into from
Jan 6, 2025
Merged

[InstCombine] Handle commuted pattern for ((X s/ C1) << C2) + X #121737

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01055b1
[InstCombine] Add pre-commit tests. NFC.
dtcxzyw Jan 5, 2025
79c3038
[InstCombine] Handle commuted pattern for `((X s/ C1) << C2) + X`
dtcxzyw Jan 5, 2025
31a6f4a
[InstCombine] Move the logic into `foldAddLikeCommutative`
dtcxzyw Jan 6, 2025
4a615c3
[InstCombine] Fix coding style. NFC.
dtcxzyw Jan 6, 2025
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24 changes: 13 additions & 11 deletions llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1326,6 +1326,18 @@ Instruction *InstCombinerImpl::foldAddLikeCommutative(Value *LHS, Value *RHS,
R->setHasNoUnsignedWrap(NUWOut);
return R;
}

// ((X s/ C1) << C2) + X => X s% -C1 where -C1 is 1 << C2
const APInt *C1, *C2;
if (match(LHS, m_Shl(m_SDiv(m_Specific(RHS), m_APInt(C1)), m_APInt(C2)))) {
APInt One(C2->getBitWidth(), 1);
APInt MinusC1 = -(*C1);
if (MinusC1 == (One << *C2)) {
Constant *NewRHS = ConstantInt::get(RHS->getType(), MinusC1);
return BinaryOperator::CreateSRem(RHS, NewRHS);
}
}

return nullptr;
}

Expand Down Expand Up @@ -1623,17 +1635,7 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
// X % C0 + (( X / C0 ) % C1) * C0 => X % (C0 * C1)
if (Value *V = SimplifyAddWithRemainder(I)) return replaceInstUsesWith(I, V);

// ((X s/ C1) << C2) + X => X s% -C1 where -C1 is 1 << C2
const APInt *C1, *C2;
if (match(LHS, m_Shl(m_SDiv(m_Specific(RHS), m_APInt(C1)), m_APInt(C2)))) {
APInt one(C2->getBitWidth(), 1);
APInt minusC1 = -(*C1);
if (minusC1 == (one << *C2)) {
Constant *NewRHS = ConstantInt::get(RHS->getType(), minusC1);
return BinaryOperator::CreateSRem(RHS, NewRHS);
}
}

const APInt *C1;
// (A & 2^C1) + A => A & (2^C1 - 1) iff bit C1 in A is a sign bit
if (match(&I, m_c_Add(m_And(m_Value(A), m_APInt(C1)), m_Deferred(A))) &&
C1->isPowerOf2() && (ComputeNumSignBits(A) > C1->countl_zero())) {
Expand Down
11 changes: 11 additions & 0 deletions llvm/test/Transforms/InstCombine/add-shl-sdiv-to-srem.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,17 @@ define i8 @add-shl-sdiv-scalar0(i8 %x) {
ret i8 %rz
}

define i8 @add-shl-sdiv-scalar0_commuted(i8 %x) {
; CHECK-LABEL: @add-shl-sdiv-scalar0_commuted(
; CHECK-NEXT: [[RZ:%.*]] = srem i8 [[X:%.*]], 4
; CHECK-NEXT: ret i8 [[RZ]]
;
%sd = sdiv i8 %x, -4
%sl = shl i8 %sd, 2
%rz = add i8 %x, %sl
ret i8 %rz
}

define i8 @add-shl-sdiv-scalar1(i8 %x) {
; CHECK-LABEL: @add-shl-sdiv-scalar1(
; CHECK-NEXT: [[RZ:%.*]] = srem i8 [[X:%.*]], 64
Expand Down
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