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Bug 1861983 - Part 6: Add more MinMax folding. r=jandem

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This reduces the `MMinMax` operations in `s.substring(1, 3)` from four to just two.

Depends on D192224

Differential Revision: https://phabricator.services.mozilla.com/D192225
This commit is contained in:
André Bargull 2023-11-03 14:23:15 +00:00
parent 830bee2c73
commit f97fefcba8
1 changed files with 71 additions and 30 deletions
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101
js/src/jit/MIR.cpp
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@ -2710,36 +2710,6 @@ MDefinition* MMinMax::foldsTo(TempAllocator& alloc) {
return lhs();
}
// Fold min/max operations with same inputs.
if (lhs()->isMinMax() || rhs()->isMinMax()) {
auto* other = lhs()->isMinMax() ? lhs()->toMinMax() : rhs()->toMinMax();
auto* operand = lhs()->isMinMax() ? rhs() : lhs();
if (operand == other->lhs() || operand == other->rhs()) {
if (isMax() == other->isMax()) {
// min(x, min(x, y)) = min(x, y)
// max(x, max(x, y)) = max(x, y)
return other;
}
if (!IsFloatingPointType(type())) {
// When neither value is NaN:
// max(x, min(x, y)) = x
// min(x, max(x, y)) = x
// Ensure that any bailouts that we depend on to guarantee that |y| is
// Int32 are not removed.
auto* otherOp = operand == other->lhs() ? other->rhs() : other->lhs();
otherOp->setGuardRangeBailoutsUnchecked();
return operand;
}
}
}
if (!lhs()->isConstant() && !rhs()->isConstant()) {
return this;
}
auto foldConstants = [&alloc](MDefinition* lhs, MDefinition* rhs,
bool isMax) -> MConstant* {
MOZ_ASSERT(lhs->type() == rhs->type());
@ -2772,6 +2742,77 @@ MDefinition* MMinMax::foldsTo(TempAllocator& alloc) {
return MConstant::New(alloc, DoubleValue(result));
};
// Try to fold the following patterns when |x| and |y| are constants.
//
// min(min(x, z), min(y, z)) = min(min(x, y), z)
// max(max(x, z), max(y, z)) = max(max(x, y), z)
// max(min(x, z), min(y, z)) = min(max(x, y), z)
// min(max(x, z), max(y, z)) = max(min(x, y), z)
if (lhs()->isMinMax() && rhs()->isMinMax()) {
do {
auto* left = lhs()->toMinMax();
auto* right = rhs()->toMinMax();
if (left->isMax() != right->isMax()) {
break;
}
MDefinition* x;
MDefinition* y;
MDefinition* z;
if (left->lhs() == right->lhs()) {
std::tie(x, y, z) = std::tuple{left->rhs(), right->rhs(), left->lhs()};
} else if (left->lhs() == right->rhs()) {
std::tie(x, y, z) = std::tuple{left->rhs(), right->lhs(), left->lhs()};
} else if (left->rhs() == right->lhs()) {
std::tie(x, y, z) = std::tuple{left->lhs(), right->rhs(), left->rhs()};
} else if (left->rhs() == right->rhs()) {
std::tie(x, y, z) = std::tuple{left->lhs(), right->lhs(), left->rhs()};
} else {
break;
}
if (!x->isConstant() || !x->toConstant()->isTypeRepresentableAsDouble() ||
!y->isConstant() || !y->toConstant()->isTypeRepresentableAsDouble()) {
break;
}
if (auto* folded = foldConstants(x, y, isMax())) {
block()->insertBefore(this, folded);
return MMinMax::New(alloc, folded, z, type(), left->isMax());
}
} while (false);
}
// Fold min/max operations with same inputs.
if (lhs()->isMinMax() || rhs()->isMinMax()) {
auto* other = lhs()->isMinMax() ? lhs()->toMinMax() : rhs()->toMinMax();
auto* operand = lhs()->isMinMax() ? rhs() : lhs();
if (operand == other->lhs() || operand == other->rhs()) {
if (isMax() == other->isMax()) {
// min(x, min(x, y)) = min(x, y)
// max(x, max(x, y)) = max(x, y)
return other;
}
if (!IsFloatingPointType(type())) {
// When neither value is NaN:
// max(x, min(x, y)) = x
// min(x, max(x, y)) = x
// Ensure that any bailouts that we depend on to guarantee that |y| is
// Int32 are not removed.
auto* otherOp = operand == other->lhs() ? other->rhs() : other->lhs();
otherOp->setGuardRangeBailoutsUnchecked();
return operand;
}
}
}
if (!lhs()->isConstant() && !rhs()->isConstant()) {
return this;
}
// Directly apply math utility to compare the rhs() and lhs() when
// they are both constants.
if (lhs()->isConstant() && rhs()->isConstant()) {