Clarify the role of the PreCodegen dummy pass#156358
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These commits modify the If this was unintentional then you should revert the changes before this PR is merged. Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt |
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I'm not familiar with that area, so the changes look neutral to me. Perhaps somebody familiar with the area should review it? @bors r? rust-lang/wg-mir-opt |
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This function doesn't have an obvious home, but there's little reason for it to be in `rustc_mir_transform`, and having it in `rustc_driver_impl::pretty` at least puts it near other callers of `write_mir_pretty`.
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This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed. Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers. |
| &dump_mir::Marker("PreCodegen"), | ||
| // Dummy pass to allow dumping the final pre-codegen MIR for testing/debugging. | ||
| // This must be the final pass! | ||
| &marker::PreCodegen, |
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I think the name should still include somewhere that this pass just dumps
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Is this pass still useful ? We now dump a file called |
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We have a bunch of mir-opt tests that currently mention PreCodegen, but if those can all be converted to use runtime-optimized then we should potentially be able to just remove PreCodegen. |
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Based on #156358 (comment) I have filed #156524 as an alternative to this PR. That PR migrates from PreCodegen to runtime-optimized, and then removes PreCodegen entirely. |
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Remove the dummy `PreCodegen` mir-opt pass, and use `runtime-optimized` instead - Alternative to rust-lang#156358. The `PreCodegen` pass doesn't do anything on its own; it was only serving as a marker to allow `-Zdump-mir` and mir-opt tests to easily dump the final MIR just before codegen. However, rust-lang#156358 (comment) pointed out that the `runtime-optimized` phase transition should dump the same MIR, so there shouldn't be any need for a separate *PreCodegen* pass. --- r? oli-obk (or compiler)
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The existing comments for this pass are somewhat confusing.
The
PreCodegenpass does nothing by itself. It exists so that-Zdump-mir(and mir-opt tests) can easily dump the final pre-codegen MIR, by dumping the input or output of PreCodegen, which happens to be run after all other passes are finished.