Shift DCE pass to optimize imaging mode code better #50631
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pchintalapudi
added
compiler:codegen
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We may also want to consider a globaldce pass here too, since we're likely killing off any use of the nearby globals as well. |
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Should we also do globalsopt as well? |
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I don't think globalopt is necessary, we already mark most of them as private, constant, and unnamed_addr to let LLVM drop them. |
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LGTM |
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Will you do the globalsDCE in another pr or did it not make a difference? |
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I didn't check, we can do it later. |
KristofferC
pushed a commit
that referenced
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Jul 24, 2023
(cherry picked from commit e23e116)
45 tasks
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Seems like a great find |
KristofferC
added a commit
that referenced
this pull request
Jul 24, 2023
Backported PRs: - [x] #50411 <!-- Fix weird dispatch of * with zero arguments --> - [x] #50202 <!-- Remove dynamic dispatch from _wait/wait2 --> - [x] #50064 <!-- Fix numbered prompt with input only with comment --> - [x] #50026 <!-- Store heapsnapshot files in tempdir() instead of current directory --> - [x] #50402 <!-- Add CPU feature helper function --> - [x] #50387 <!-- update newpages pointer after actually sweeping pages --> - [x] #50424 <!-- avoid potential type-instability in _replace_(str, ...) --> - [x] #50444 <!-- Optimize getfield lowering to avoid boxing in some cases --> - [x] #50474 <!-- docs: Fix a `!!! note` which was miscapitalized --> - [x] #50466 <!-- relax assertion involving pg->nold to reflect that it may be a bit in… --> - [x] #50490 <!-- Fix compat annotation for italic printstyled --> - [x] #50488 <!-- fix typo in `Base.isassigned` with `Tridiagonal` --> - [x] #50476 <!-- Profile: Add specifying dir for `take_heap_snapshot` and handling if current dir is unwritable --> - [x] #50461 <!-- fix typo in the --gcthreads argument description --> - [x] #50528 <!-- ssair: Correctly handle stmt insertion at end of basic block --> - [x] #50533 <!-- ensure internal_obj_base_ptr checks whether objects past freelist pointer are in freelist --> - [x] #49322 <!-- improve cat design / performance --> - [x] #50540 <!-- gc: remove over-eager assertion --> - [x] #50542 <!-- gf: remove unnecessary assert cycle==depth --> - [x] #50559 <!-- Expand kwcall lowering positional default check to vararg --> - [x] #50058 <!-- Add unwrapping mechanism for triangular mul and solves --> - [x] #50551 <!-- typeintersect: also record chained `innervars` --> - [x] #50552 <!-- read(io, Char): fix read with too many leading ones --> - [x] #50541 <!-- precompile: ensure globals are not accidentally created where disallowed --> - [x] #50576 <!-- use atomic compare exchange when setting the GC mark-bit --> - [x] #50578 <!-- gf: make method overwrite/delete an error during precompile --> - [x] #50516 <!-- Fix visibility of assert on GCC12/13 --> - [x] #50597 <!-- Fix memory corruption if task is launched inside finalizer --> - [x] #50591 <!-- build: fix various makefile bugs --> - [x] #50599 <!-- faster invalid object lookup in conservative gc --> - [x] #50634 <!-- 🤖 [master] Bump the SparseArrays stdlib from b4b0e72 to 99c99b4 --> - [x] #50639 <!-- Backport LLVM patches to fix various issues. --> - [x] #50546 <!-- Revert storage of method instance in LineInfoNode --> - [x] #50631 <!-- Shift DCE pass to optimize imaging mode code better --> - [x] #50525 <!-- only check that values are finite in `generic_lufact` when `check=true` --> - [x] #50587 <!-- isassigned for ranges with BigInt indices --> - [x] #50144 <!-- Page based heap size heuristics --> Need manual backport: - [ ] #50595 <!-- Rename ENV variable `JULIA_USE_NEW_PARSER` -> `JULIA_USE_FLISP_PARSER` --> Non-merged PRs with backport label: - [ ] #50637 <!-- Remove SparseArrays legacy code --> - [ ] #50618 <!-- inference: continue const-prop' when concrete-eval returns non-inlineable --> - [ ] #50598 <!-- only limit types in stack traces in the REPL --> - [ ] #50594 <!-- Disallow non-index Integer types in isassigned --> - [ ] #50568 <!-- `Array(::AbstractRange)` should return an `Array` --> - [ ] #50523 <!-- Avoid generic call in most cases for getproperty --> - [ ] #50172 <!-- print feature flags used for matching pkgimage -->
KristofferC
removed
the
backport 1.10
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While stripping out literal pointer values and replacing them with imaging mode's loads from global variables, it turns out that codegen emits LLVM IR instructions to load builtin intrinsics that are later removed when codegen lowers builtin calls (e.g. Core.arrayset, Core.not_int, etc). DCE is able to remove this dead code, but we weren't running it before the initial simplifycfg pass, which caused simplifycfg to become more conservative about moving operations around the loads from global variables.
I personally think we should backport this to 1.10 as it probably improves the native code's quality by a decent fraction.
Diff: https://www.diffchecker.com/iwo6mJUs/