Allow constprop to improve constant results to Bottom#45146
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aviatesk
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May 2, 2022
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aviatesk
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May 2, 2022
This is consistent with what we would do for a non-constant return. This helps the compiler dump less code onto LLVM in situations where there is a big basic block that our constprop can see is dead. That said, for that particular situation, it might be better to have a constant propagation pass at the IR level that runs after inlining. We can revisit that after #44660.
vtjnash
reviewed
May 3, 2022
| add_remark!(interp, sv, "[constprop] Disabled by entry heuristic (unimprovable return type)") | ||
| if isa(rt, Const) | ||
| if result.edge_effects.nothrow !== ALWAYS_TRUE | ||
| # Could still be improved to Bottom (or at least could see the effects improved) |
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This seems specifically the case that function was intended to ignore as a possibility. I think a more correct version of this PR would be removing this function entirely, and remarking here only that we do const_prop as a pre-inlining optimization, so the return result is irrelevant to whether it may improve the quality of the inlined code.
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This is consistent with what we would do for a non-constant return.
This helps the compiler dump less code onto LLVM in situations
where there is a big basic block that our constprop can see is
dead. That said, for that particular situation, it might be better
to have a constant propagation pass at the IR level that runs
after inlining. We can revisit that after #44660.