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Eliminate some unnecessary clamping in ClampUnsafeAccesses (#6297) #6654

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merged 4 commits into from
Mar 22, 2022
Merged

Eliminate some unnecessary clamping in ClampUnsafeAccesses (#6297) #6654

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9dd0908
Eliminate some unnecessary clamping in ClampUnsafeAccesses (#6297)
steven-johnson Mar 18, 2022
3e2995a
Update ClampUnsafeAccesses.cpp
steven-johnson Mar 18, 2022
2a126a0
Update ClampUnsafeAccesses.cpp
steven-johnson Mar 18, 2022
ed51a50
Update ClampUnsafeAccesses.cpp
steven-johnson Mar 18, 2022
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28 changes: 26 additions & 2 deletions src/ClampUnsafeAccesses.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,14 +11,36 @@ namespace {
struct ClampUnsafeAccesses : IRMutator {
const std::map<std::string, Function> &env;
FuncValueBounds &func_bounds;
std::vector<std::string> realizes_inside_current_producer;

ClampUnsafeAccesses(const std::map<std::string, Function> &env, FuncValueBounds &func_bounds)
: env(env), func_bounds(func_bounds) {
}

bool is_realize_inside_current_producer(const std::string &n) const {
return std::find(realizes_inside_current_producer.begin(),
realizes_inside_current_producer.end(), n) != realizes_inside_current_producer.end();
}

protected:
using IRMutator::visit;

Stmt visit(const ProducerConsumer *op) override {
if (op->is_producer) {
ScopedValue<std::vector<std::string>> r(realizes_inside_current_producer, {});
return IRMutator::visit(op);
} else {
return IRMutator::visit(op);
}
}

Stmt visit(const Realize *op) override {
realizes_inside_current_producer.push_back(op->name);
auto new_stmt = IRMutator::visit(op);
realizes_inside_current_producer.pop_back();
return new_stmt;
}

Expr visit(const Let *let) override {
return visit_let<Let, Expr>(let);
}
Expand All @@ -35,11 +57,13 @@ struct ClampUnsafeAccesses : IRMutator {
}

Expr visit(const Call *call) override {
if (call->call_type == Call::Halide && is_inside_indexing) {
// Note that if the call's realization is inside the current producer (i.e. it's caller),
// the compute bounds of this call should be known to cover all loaded values, so we
// should be able to safely skip the clamp injection (see #6297).
if (call->call_type == Call::Halide && is_inside_indexing && !is_realize_inside_current_producer(call->name)) {
auto bounds = func_bounds.at({call->name, call->value_index});
if (bounds_smaller_than_type(bounds, call->type)) {
// TODO(#6297): check that the clamped function's allocation bounds might be wider than its compute bounds

auto [new_args, changed] = mutate_with_changes(call->args);
Expr new_call = changed ? call : Call::make(call->type, call->name, new_args, call->call_type, call->func, call->value_index, call->image, call->param);
return Max::make(Min::make(new_call, std::move(bounds.max)), std::move(bounds.min));
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