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a611f8dbfc
rust/compiler
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Yuki Okushi a611f8dbfc
Rollup merge of #79882 - wecing:master, r=oli-obk 
Fix issue #78496

EarlyOtherwiseBranch finds MIR structures like:

```
bb0: {
  ...
  _2 = discriminant(X)
  ...
  switchInt(_2) -> [1_isize: bb1, otherwise: bb3]
}
bb1: {
  ...
  _3 = discriminant(Y)
  ...
  switchInt(_3) -> [1_isize: bb2, otherwise: bb3]
}
bb2: {...}
bb3: {...}
```

And transforms them into something like:

```
bb0: {
  ...
  _2 = discriminant(X)
  _3 = discriminant(Y)
  _4 = Eq(_2, _3)
  switchInt(_4) -> [true: bb4, otherwise: bb3]
}
bb2: {...} // unchanged
bb3: {...} // unchanged
bb4: {
  switchInt(_2) -> [1_isize: bb2, otherwise: bb3]
}
```

But that is not always a safe thing to do -- sometimes the early `otherwise` branch is necessary so the later block could assume the value of `discriminant(X)`.

I am not totally sure what's the best way to detect that, but fixing #78496 should be easy -- we just check if `X` is a sub-expression of `Y`. A more precise test might be to check if `Y` contains a `Downcast(1)` of `X`, but I think this might be good enough.

Fix #78496
2020-12-17 11:43:59 +09:00
..
rustc just max_level_info 2020-09-11 09:37:51 -07:00
rustc_apfloat Backport another LLVM commit to rustc_apfloat 2020-10-04 02:02:25 +02:00
rustc_arena Use specialization to avoid copying 2020-11-20 21:02:09 +01:00
rustc_ast Accept arbitrary expressions in key-value attributes at parse time 2020-12-09 21:37:32 +03:00
rustc_ast_lowering Rollup merge of #79051 - LeSeulArtichaut:if-let-guard, r=matthewjasper 2020-12-17 11:43:55 +09:00
rustc_ast_passes Rollup merge of #79851 - camelid:better-error-for-default-fn, r=davidtwco 2020-12-10 21:33:10 -08:00
rustc_ast_pretty Rollup merge of #79016 - fanzier:underscore-expressions, r=petrochenkov 2020-11-15 13:39:48 +01:00
rustc_attr Get rid of clean::Deprecation 2020-12-14 22:00:46 -05:00
rustc_builtin_macros fix clippy::unnecessary_filter_map 2020-12-11 23:02:19 +01:00
rustc_codegen_cranelift cg_clif: fix build with split dwarf 2020-12-16 10:33:48 +00:00
rustc_codegen_llvm cg_llvm: split dwarf filename and comp dir 2020-12-16 10:33:52 +00:00
rustc_codegen_ssa compiletest: add split dwarf compare mode 2020-12-16 10:33:51 +00:00
rustc_data_structures Rename optin_builtin_traits to auto_traits 2020-11-23 14:14:06 -08:00
rustc_driver Fix unknown-crate when using self-profile with rustdoc 2020-12-01 12:54:03 -05:00
rustc_error_codes Rollup merge of #79639 - sasurau4:feature/add-long-explanation-E0212, r=GuillaumeGomez 2020-12-10 21:33:04 -08:00
rustc_errors Rollup merge of #74293 - GuillaumeGomez:rustdoc-test-compiler-output-color, r=jyn514 2020-11-17 16:13:46 +01:00
rustc_expand Remove some no longer necessary #[cfg(test)]s 2020-12-12 19:20:37 +03:00
rustc_feature tidy: Re-enable check for inline unit tests 2020-12-12 19:18:44 +03:00
rustc_fs_util Remove unused code from remaining compiler crates 2020-10-14 04:14:32 +02:00
rustc_graphviz Rust coverage before splitting instrument_coverage.rs 2020-11-05 18:24:12 -08:00
rustc_hir Rollup merge of #79051 - LeSeulArtichaut:if-let-guard, r=matthewjasper 2020-12-17 11:43:55 +09:00
rustc_hir_pretty Rollup merge of #79051 - LeSeulArtichaut:if-let-guard, r=matthewjasper 2020-12-17 11:43:55 +09:00
rustc_incremental Auto merge of #74967 - Aaron1011:feature/incr-def-path-table, r=pnkfelix 2020-12-01 14:30:02 +00:00
rustc_index Stabilise then 2020-11-22 13:45:14 +00:00
rustc_infer simplify if let Some(_) = x to if x.is_some() (clippy::redundant_pattern_matching) 2020-12-08 20:27:49 +01:00
rustc_interface Convenience funcs for some_option.unwrap_or(...) 2020-12-14 17:27:27 -08:00
rustc_lexer Fix some clippy lints 2020-12-03 17:08:19 -05:00
rustc_lint don't create owned values for comparison (clippy::cmp_owned) 2020-12-08 20:27:48 +01:00
rustc_lint_defs Validate naked functions definitions 2020-12-07 00:00:00 +00:00
rustc_llvm llvm: update ffi bindings for split dwarf 2020-12-16 10:31:42 +00:00
rustc_macros ./x.py fmt 2020-12-13 13:36:01 -08:00
rustc_metadata Convenience funcs for some_option.unwrap_or(...) 2020-12-14 17:27:27 -08:00
rustc_middle Allow since="TBD" for rustc_deprecated 2020-12-16 13:21:24 -05:00
rustc_mir Rollup merge of #79882 - wecing:master, r=oli-obk 2020-12-17 11:43:59 +09:00
rustc_mir_build Rollup merge of #79051 - LeSeulArtichaut:if-let-guard, r=matthewjasper 2020-12-17 11:43:55 +09:00
rustc_parse Auto merge of #79978 - Aaron1011:fix/capture-broken-token, r=petrochenkov 2020-12-13 19:31:06 +00:00
rustc_parse_format /nightly/nightly-rustc 2020-09-23 21:51:56 +02:00
rustc_passes Rollup merge of #79877 - bstrie:depinfut, r=oli-obk 2020-12-17 11:43:57 +09:00
rustc_plugin_impl Store ForeignItem in a side table. 2020-11-26 21:29:27 +01:00
rustc_privacy Remove ForeignMod struct. 2020-11-26 21:32:27 +01:00
rustc_query_system Use def_path_hash_to_def_id when re-using a RawDefId 2020-12-10 16:04:19 -05:00
rustc_resolve Resolve enum field visibility correctly 2020-12-12 14:04:59 -08:00
rustc_save_analysis Remove ForeignMod struct. 2020-11-26 21:32:27 +01:00
rustc_serialize Fix some clippy lints 2020-12-03 17:08:19 -05:00
rustc_session cg_llvm: split dwarf filename and comp dir 2020-12-16 10:33:52 +00:00
rustc_span Switch to Symbol for item.name 2020-12-14 22:19:15 -05:00
rustc_symbol_mangling Convenience funcs for some_option.unwrap_or(...) 2020-12-14 17:27:27 -08:00
rustc_target Rollup merge of #79917 - sivadeilra:asm_symbols, r=petrochenkov 2020-12-10 21:33:19 -08:00
rustc_trait_selection use if let Some(x) = .. instead of ...map(|x|) to conditionally run fns that return () (clippy::option_map_unit_fn) 2020-12-11 23:02:19 +01:00
rustc_traits Don't run resolve_vars_if_possible in normalize_erasing_regions 2020-11-18 12:25:36 -05:00
rustc_ty_utils Be cautious of calling upvar_tys before mir 2020-11-29 19:20:28 -05:00
rustc_type_ir Fix typo in DebruijnIndex documentation 2020-12-12 16:13:06 +01:00
rustc_typeck Rollup merge of #79051 - LeSeulArtichaut:if-let-guard, r=matthewjasper 2020-12-17 11:43:55 +09:00