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[MLIR][Arith] add and(a, or(a,b)) folder #138998

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[MLIR][Arith] add and(a, or(a,b)) folder #138998

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12 changes: 12 additions & 0 deletions mlir/lib/Dialect/Arith/IR/ArithOps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -896,6 +896,18 @@ OpFoldResult arith::AndIOp::fold(FoldAdaptor adaptor) {
if (Value result = foldAndIofAndI(*this))
return result;

/// and(a, or(a, b)) -> a
for (int i = 0; i < 2; i++) {
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Use pre-increment: https://llvm.org/docs/CodingStandards.html#prefer-preincrement

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@joker-eph joker-eph Jun 3, 2025 •
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I would really rather avoid raw loops entirely.

Can this just be written as:

for (Value operand : getOperands()) {
  if (auto orOp = operand..getDefiningOp<arith::OrIOp>()) {

(same for the second loop)

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so the reason that might be hard is that we need both the original operand, and also the "other" operand. In the loop form that can be written as get operand[i] and operand[1-i], and/or operand[i] and i == 0 ? operand[1] : operand[0]. Not sure how to do that as a single foreach iterator

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@joker-eph joker-eph Jun 4, 2025 •
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Oh I missed the 1-i in the code, this looks like all code obfuscation to me.

I would write this with a lambda instead, something like:

/// and(or(a, b), a) -> a
auto matchAndOr = [&] (Value lhs, Value rhs) {
  auto orOp = lhs.getDefiningOp<arith::OrIOp>();
   if (!orOp) return false;
   for (Value orOperand : orOp->getOperands())
     if (orOperand == rhs) return true;
   return false;
};

Value lhs = getOperand(0);
Value rhs = getOperand(1);
if (matchAndOr(lhs, rhs)) return rhs;

/// `and` is commutative, swap the operands: `and(a, or(a, b)) -> a`
if (matchAndOr(rhs, lhs)) return lhs;

auto a = getOperand(1 - i);
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nit: Spell out the full type here since it's not immediately obvious based on the RHS: https://llvm.org/docs/CodingStandards.html#use-auto-type-deduction-to-make-code-more-readable

if (auto orOp = getOperand(i).getDefiningOp<arith::OrIOp>()) {
for (int j = 0; j < 2; j++) {
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also here

if (orOp->getOperand(j) == a) {
return a;
}
Comment on lines +904 to +906
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Suggested change
if (orOp->getOperand(j) == a) {
return a;
}
if (orOp->getOperand(j) == a)
return a;

}
}
}

return constFoldBinaryOp<IntegerAttr>(
adaptor.getOperands(),
[](APInt a, const APInt &b) { return std::move(a) & b; });
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9 changes: 9 additions & 0 deletions mlir/test/Dialect/Arith/canonicalize.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -2901,6 +2901,15 @@ func.func @andand3(%a : i32, %b : i32) -> i32 {
return %res : i32
}

// CHECK-LABEL: @andor
// CHECK-SAME: (%[[A:.*]]: i32, %[[B:.*]]: i32)
// CHECK: return %[[A]]
func.func @andor(%a : i32, %b : i32) -> i32 {
%c = arith.ori %a, %b : i32
%res = arith.andi %a, %b : i32
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should it be arith.andi %a, %c?

return %res : i32
}

// -----

// CHECK-LABEL: @truncIShrSIToTrunciShrUI
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