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Implement constant propagation on top of MIR SSA analysis #116012
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This PR changes MIR cc @oli-obk, @RalfJung, @JakobDegen, @davidtwco, @celinval, @vakaras Some changes occurred to the CTFE / Miri engine cc @rust-lang/miri The Miri subtree was changed cc @rust-lang/miri Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt |
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☔ The latest upstream changes (presumably #116027) made this pull request unmergeable. Please resolve the merge conflicts. |
This PR changes MIR cc @oli-obk, @RalfJung, @JakobDegen, @davidtwco, @celinval, @vakaras The Miri subtree was changed cc @rust-lang/miri Some changes occurred to the CTFE / Miri engine cc @rust-lang/miri Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt |
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☔ The latest upstream changes (presumably #115696) made this pull request unmergeable. Please resolve the merge conflicts. |
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@bors try @rust-timer queue |
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Implement constant propagation on top of MIR SSA analysis This implements the idea I proposed in rust-lang#110719 (comment) Based on rust-lang#109597 The value numbering "GVN" pass formulates each rvalue that appears in MIR with an abstract form (the `Value` enum), and assigns an integer `VnIndex` to each. This abstract form can be used to deduplicate values, reusing an earlier local that holds the same value instead of recomputing. This part is proposed in rust-lang#109597. From this abstract representation, we can perform more involved simplifications, for example in rust-lang#111344. With the abstract representation `Value`, we can also attempt to evaluate each to a constant using the interpreter. This builds a `VnIndex -> OpTy` map. From this map, we can opportunistically replace an operand or a rvalue with a constant if their value has an associated `OpTy`. The most relevant commit is [Evaluated computed values to constants.](rust-lang@2767c49)" r? `@oli-obk`
☀️ Try build successful - checks-actions |
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☀️ Try build successful - checks-actions |
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Finished benchmarking commit (7b24347): comparison URL. Overall result: ❌✅ regressions and improvements - ACTION NEEDEDBenchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf. Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @bors rollup=never Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)ResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Binary sizeResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Bootstrap: 634.28s -> 634.677s (0.06%) |
Looks to me like the timeout was in uploading to s3 @bors retry |
☀️ Test successful - checks-actions |
Finished benchmarking commit (8d76d07): comparison URL. Overall result: ❌✅ regressions and improvements - ACTION NEEDEDNext Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)ResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Binary sizeResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Bootstrap: 670.291s -> 668.991s (-0.19%) |
It seems given the positives for this change and the fact that improvements outweigh regressions, we can call this triaged. @rustbot label: +perf-regression-triaged |
Fold arithmetic identities in GVN Extracted from rust-lang#111344 This PR implements a few arithmetic folds for unary and binary operations. This should take care of the missed optimizations introduced by rust-lang#116012.
Fold arithmetic identities in GVN Extracted from rust-lang#111344 This PR implements a few arithmetic folds for unary and binary operations. This should take care of the missed optimizations introduced by rust-lang#116012.
Fold arithmetic identities in GVN Extracted from rust-lang/rust#111344 This PR implements a few arithmetic folds for unary and binary operations. This should take care of the missed optimizations introduced by rust-lang/rust#116012.
I'm only just seeing this... this is amazing, old const-prop is gone. :) Thanks a ton @cjgillot! |
…i-obk Remove const_prop.rs Removed const_prop.rs and moved its contents to const_prop_lint.rs and dataflow_const_prop.rs where they are used. const_prop.rs does not actually do any const propagation any more. After rust-lang#116012 all it contains is code that is used by const_prop_lint.rs and one macro that is used by dataflow_const_prop.rs. So it made sense to just move it to those two places and remove this file.
Rollup merge of rust-lang#121260 - gurry:constprop-lint-cleanup, r=oli-obk Remove const_prop.rs Removed const_prop.rs and moved its contents to const_prop_lint.rs and dataflow_const_prop.rs where they are used. const_prop.rs does not actually do any const propagation any more. After rust-lang#116012 all it contains is code that is used by const_prop_lint.rs and one macro that is used by dataflow_const_prop.rs. So it made sense to just move it to those two places and remove this file.
Add FileCheck annotations to const_prop tests Unblocks rust-lang/rust#116012 Advances rust-lang/rust#116971
Add FileCheck annotations to const_prop tests Unblocks rust-lang/rust#116012 Advances rust-lang/rust#116971
This implements the idea I proposed in #110719 (comment)
Based on #109597
The value numbering "GVN" pass formulates each rvalue that appears in MIR with an abstract form (the
Value
enum), and assigns an integerVnIndex
to each. This abstract form can be used to deduplicate values, reusing an earlier local that holds the same value instead of recomputing. This part is proposed in #109597.From this abstract representation, we can perform more involved simplifications, for example in #111344.
With the abstract representation
Value
, we can also attempt to evaluate each to a constant using the interpreter. This builds aVnIndex -> OpTy
map. From this map, we can opportunistically replace an operand or a rvalue with a constant if their value has an associatedOpTy
.The most relevant commit is Evaluated computed values to constants."
r? @oli-obk