Add ClampUnsafeAccesses pass. #6294
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Inject clamps around func calls h(...) when all the following conditions hold: 1. The call is in an indexing context, such as: f(x) = g(h(x)); 2. The schedule for f uses RoundUp or ShiftInwards 3. h is not compute_at within f's produce node 4. The FuncValueBounds of h are smaller than those of its type Conditions (3) and (4) are not yet implemented.
abadams
reviewed
Oct 7, 2021
abadams
reviewed
Oct 7, 2021
abadams
reviewed
Oct 7, 2021
abadams
reviewed
Oct 7, 2021
abadams
reviewed
Oct 7, 2021
abadams
reviewed
Oct 7, 2021
src/ClampUnsafeAccesses.cpp
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| if (is_inside_indexing) { | ||
| auto bounds = func_bounds.at({call->name, call->value_index}); | ||
| if (bounds_smaller_than_type(bounds, call->type)) { | ||
| // TODO: check that the clamped function's allocation bounds might be wider than its compute bounds |
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Oh, I figured this PR was blocked on implementing this.
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Done. Opened issue #6297 to track this.
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It fixes a miscompilation. I think we can live with a few extra ops instead in the short term.
abadams
approved these changes
Oct 7, 2021
| // TODO(#6297): check that the clamped function's allocation bounds might be wider than its compute bounds | ||
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| 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); |
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(resurrecting a zombie PR...)
Uh, is this right? Shouldn't it be !changed ? call : ... ?
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Yeeeep, that looks like a typo. Want to try changing it to see if tests fail?
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Inject clamps around func calls h(...) when all the following conditions hold:
Fixes #6131