Rollup of 9 pull requests #33632
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Rollup of 9 pull requests #33632
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Manishearth
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May 14, 2016
Manishearth
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- Successful merges: Only break critical edges where actually needed #33544, [MIR] Enhance the SimplifyCfg pass to merge consecutive blocks #33552, Don't use env::current_exe with libbacktrace #33554, Remove unification despite ambiguity in projection #33555, Use symlink_metadata in tidy to avoid panicking on broken symlinks. #33560, [MIR trans] Optimize trans for biased switches #33566, Support references to outer type params for assoc consts #33572, trans-collector: Assorted fixes and refactorings needed for making trans collector-driven. #33574, Plumb inference obligations through selection, take 2 #33576
- Failed merges:
Currently, to prepare for MIR trans, we break _all_ critical edges, although we only actually need to do this for edges originating from a call that gets translated to an invoke instruction in LLVM. This has the unfortunate effect of undoing a bunch of the things that SimplifyCfg has done. A particularly bad case arises when you have a C-like enum with N variants and a derived PartialEq implementation. In that case, the match on the (&lhs, &rhs) tuple gets translated into nested matches with N arms each and a basic block each, resulting in N² basic blocks. SimplifyCfg reduces that to roughly 2*N basic blocks, but breaking the critical edges means that we go back to N². In nickel.rs, there is such an enum with roughly N=800. So we get about 640K basic blocks or 2.5M lines of LLVM IR. LLVM takes a while to reduce that to the final "disr_a == disr_b". So before this patch, we had 2.5M lines of IR with 640K basic blocks, which took about about 3.6s in LLVM to get optimized and translated. After this patch, we get about 650K lines with about 1.6K basic blocks and spent a little less than 0.2s in LLVM. cc rust-lang#33111
Currently, all switches in MIR are exhausitive, meaning that we can have a lot of arms that all go to the same basic block, the extreme case being an if-let expression which results in just 2 possible cases, be might end up with hundreds of arms for large enums. To improve this situation and give LLVM less code to chew on, we can detect whether there's a pre-dominant target basic block in a switch and then promote this to be the default target, not translating the corresponding arms at all. In combination with rust-lang#33544 this makes unoptimized MIR trans of nickel.rs as fast as using old trans and greatly improves the times for optimized builds, which are only 30-40% slower instead of ~300%. cc rust-lang#33111
…:empty() where appropriate.
If the path we give to libbacktrace doesn't actually correspond to the current process, libbacktrace will segfault *at best*. cc rust-lang#21889
… r=Aatch Only break critical edges where actually needed Currently, to prepare for MIR trans, we break _all_ critical edges, although we only actually need to do this for edges originating from a call that gets translated to an invoke instruction in LLVM. This has the unfortunate effect of undoing a bunch of the things that SimplifyCfg has done. A particularly bad case arises when you have a C-like enum with N variants and a derived PartialEq implementation. In that case, the match on the (&lhs, &rhs) tuple gets translated into nested matches with N arms each and a basic block each, resulting in N² basic blocks. SimplifyCfg reduces that to roughly 2*N basic blocks, but breaking the critical edges means that we go back to N². In nickel.rs, there is such an enum with roughly N=800. So we get about 640K basic blocks or 2.5M lines of LLVM IR. LLVM takes a while to reduce that to the final "disr_a == disr_b". So before this patch, we had 2.5M lines of IR with 640K basic blocks, which took about about 3.6s in LLVM to get optimized and translated. After this patch, we get about 650K lines with about 1.6K basic blocks and spent a little less than 0.2s in LLVM. cc rust-lang#33111 r? @Aatch
[MIR] Enhance the SimplifyCfg pass to merge consecutive blocks Updated from rust-lang#30238, including the changes suggested by @Aatch.
…hton Don't use env::current_exe with libbacktrace If the path we give to libbacktrace doesn't actually correspond to the current process, libbacktrace will segfault *at best*. cc rust-lang#21889 r? @alexcrichton cc @semarie
…sakis Remove unification despite ambiguity in projection Turns out that closures aren't explicitly considered in `project.rs`, so the ambiguity handling w.r.t. closures can just be removed as the change done in `select.rs` covers it. r? @nikomatsakis
Use symlink_metadata in tidy to avoid panicking on broken symlinks. r? @alexcrichton
[MIR trans] Optimize trans for biased switches Currently, all switches in MIR are exhausitive, meaning that we can have a lot of arms that all go to the same basic block, the extreme case being an if-let expression which results in just 2 possible cases, be might end up with hundreds of arms for large enums. To improve this situation and give LLVM less code to chew on, we can detect whether there's a pre-dominant target basic block in a switch and then promote this to be the default target, not translating the corresponding arms at all. In combination with rust-lang#33544 this makes unoptimized MIR trans of nickel.rs as fast as using old trans and greatly improves the times for optimized builds, which are only 30-40% slower instead of ~300%. cc rust-lang#33111
Support references to outer type params for assoc consts Fixes rust-lang#28809 r? @eddyb
… r=nikomatsakis trans-collector: Assorted fixes and refactorings needed for making trans collector-driven. As the title says. The messages on the individual commits should do a good job of explaining what they are about. r? @nikomatsakis
Plumb inference obligations through selection, take 2 Using a `SnapshotVec` and dumping inferred obligations into `Vtable` variants. r? @nikomatsakis
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(rust_highfive has picked a reviewer for you, use r? to override) |
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@bors r+ p=10 |
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📌 Commit 61d87f0 has been approved by |
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