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Track whether or not let expressions failed to solve in solver #7982

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merged 14 commits into from
Jan 26, 2024
Merged

Track whether or not let expressions failed to solve in solver #7982

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23afcc9
Track whether or not let expressions failed to solve in solver
abadams Dec 6, 2023
f7551a8
Merge remote-tracking branch 'origin/main' into abadams/track_failedn…
abadams Dec 7, 2023
bc89e96
Merge branch 'main' into abadams/track_failedness_through_solver_lets
steven-johnson Dec 8, 2023
2246721
Remove surplus comma
abadams Jan 22, 2024
9249e4a
Merge remote-tracking branch 'origin/main' into abadams/track_failedn…
abadams Jan 22, 2024
c5578b2
Fix use of uninitialized value that could cause bad transformation
abadams Jan 22, 2024
2281f01
Merge branch 'abadams/track_failedness_through_solver_lets' of https:…
abadams Jan 22, 2024
8c20cdf
Merge remote-tracking branch 'origin/main' into abadams/track_failedn…
abadams Jan 24, 2024
77edbbb
Merge remote-tracking branch 'origin/main' into abadams/track_failedn…
abadams Jan 24, 2024
6f5b34d
Merge branch 'main' into abadams/track_failedness_through_solver_lets
steven-johnson Jan 24, 2024
85d7edd
trigger buildbots
steven-johnson Jan 25, 2024
ccea846
trigger buildbots
steven-johnson Jan 25, 2024
9bd13a5
trigger buildbots
steven-johnson Jan 25, 2024
dae1bfb
trigger buildbots
steven-johnson Jan 26, 2024
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36 changes: 27 additions & 9 deletions src/Solve.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44,18 +44,22 @@ class SolveExpression : public IRMutator {
map<Expr, CacheEntry, ExprCompare>::iterator iter = cache.find(e);
if (iter == cache.end()) {
// Not in the cache, call the base class version.
debug(4) << "Mutating " << e << " (" << uses_var << ")\n";
debug(4) << "Mutating " << e << " (" << uses_var << ", " << failed << ")\n";
bool old_uses_var = uses_var;
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I sure which C++ had a terse way to express this pattern (that wasn't an RIAA class)...

uses_var = false;
bool old_failed = failed;
failed = false;
Expr new_e = IRMutator::mutate(e);
CacheEntry entry = {new_e, uses_var};
CacheEntry entry = {new_e, uses_var, failed};
uses_var = old_uses_var || uses_var;
failed = old_failed || failed;
cache[e] = entry;
debug(4) << "(Miss) Rewrote " << e << " -> " << new_e << " (" << uses_var << ")\n";
debug(4) << "(Miss) Rewrote " << e << " -> " << new_e << " (" << uses_var << ", " << failed << ")\n";
return new_e;
} else {
// Cache hit.
uses_var = uses_var || iter->second.uses_var;
failed = failed || iter->second.failed;
debug(4) << "(Hit) Rewrote " << e << " -> " << iter->second.expr << " (" << uses_var << ")\n";
return iter->second.expr;
}
Expand All @@ -75,7 +79,7 @@ class SolveExpression : public IRMutator {
// stateless, so we can cache everything.
struct CacheEntry {
Expr expr;
bool uses_var;
bool uses_var, failed;
};
map<Expr, CacheEntry, ExprCompare> cache;

Expand Down Expand Up @@ -388,16 +392,26 @@ class SolveExpression : public IRMutator {
const Mul *mul_a = a.as<Mul>();
Expr expr;
if (a_uses_var && !b_uses_var) {
const int64_t *ib = as_const_int(b);
auto is_multiple_of_b = [&](const Expr &e) {
if (ib) {
int64_t r;
reduce_expr_modulo(e, *ib, &r);
return r == 0;
} else {
return can_prove(e / b * b == e);
}
};
if (add_a && !a_failed &&
can_prove(add_a->a / b * b == add_a->a)) {
is_multiple_of_b(add_a->a)) {
// (f(x) + a) / b -> f(x) / b + a / b
expr = mutate(simplify(add_a->a / b) + add_a->b / b);
} else if (sub_a && !a_failed &&
can_prove(sub_a->a / b * b == sub_a->a)) {
is_multiple_of_b(sub_a->a)) {
// (f(x) - a) / b -> f(x) / b - a / b
expr = mutate(simplify(sub_a->a / b) - sub_a->b / b);
} else if (mul_a && !a_failed && no_overflow_int(op->type) &&
can_prove(mul_a->b / b * b == mul_a->b)) {
is_multiple_of_b(mul_a->b)) {
// (f(x) * a) / b -> f(x) * (a / b)
expr = mutate(mul_a->a * (mul_a->b / b));
}
Expand Down Expand Up @@ -776,6 +790,7 @@ class SolveExpression : public IRMutator {
} else if (scope.contains(op->name)) {
CacheEntry e = scope.get(op->name);
uses_var = uses_var || e.uses_var;
failed = failed || e.failed;
return e.expr;
} else if (external_scope.contains(op->name)) {
Expr e = external_scope.get(op->name);
Expand All @@ -790,11 +805,14 @@ class SolveExpression : public IRMutator {

Expr visit(const Let *op) override {
bool old_uses_var = uses_var;
bool old_failed = failed;
uses_var = false;
failed = false;
Expr value = mutate(op->value);
CacheEntry e = {value, uses_var};

CacheEntry e = {value, uses_var, failed};
uses_var = old_uses_var;
failed = old_failed;

ScopedBinding<CacheEntry> bind(scope, op->name, e);
return mutate(op->body);
}
Expand Down