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Middle-end support for local allocs #491
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(For the files I own.)
Apart from the backend changes I'll review the whole of this PR. |
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My review is for backend changes only.
Question: mode
replaces a place-holder Alloc_heap
throughout cmmgen.ml
in this PR, except a couple of places related to unboxed numbers: is_unboxed_number_cmm
and transl_let
. Is it intentional?
I'll look at this, thanks for spotting that. |
Thanks for pointing this out, I'll have a proper look on Monday. The Cmm number unboxing is tricky, and there might well be something wrong here. But as a quick note: it is always safe to allocate a float or boxed integer as There are a couple of places where Alloc_heap is unconditionally used, including:
(All of these could be made to use local allocations with even more propagation of |
I also think there might be something wrong, but expect to fix it today. (update: we need to discuss on Monday!) |
I've just had a look:
|
Changes Lambda by introducing: - Allocation modes (Alloc_heap / Alloc_local) on allocating primitives - Region boundaries (Lregion e) delimiting lifetime of local allocs - Tail call markers (Apply_tail) on applications The last of these is the trickiest: tail calls from within a region should end the region after the arguments to the tail call have been evaluated, but before control is transferred. Two middle-ends (Closure and Flambda1) now support local allocs. The trickiest part by far is correctly maintaining allocation modes during inlining, particularly when the application being inlined is a partial or over-application, or a tail call. Flambda2 here has only stub support for local allocs. The remaining changes to ocaml/ are the minimal ones required for CI. Full support for local allocs in the ocaml/ subtree will appear later.
Co-authored-by: Xavier Clerc <[email protected]>
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This is ok to merge once CI passes. |
173842c Merge flambda-backend changes ed7eba2 Remove leading space from LINE. (#484) bd61170 Bump magic numbers (#5) c50c47d Add CI builds with local allocations enabled 1412792 Move local allocations support behind '-extension local' 6d8e42a Better tail call behaviour in caml_applyN c7dac3d Typemod: toplevel bindings escape even if no variables are bound 82d6c3e Several fixes for partial application and currying d05c70c Pprintast support for new local syntax e0e62fc Typecheck x |> f y as (f y x), not ((f y) x) d7e34ce Remove autogeneration of @ocaml.curry b9a0593 Port #493 0a872d9 Code review fixes from #491 6c168bb Remove local allocation counting 3c6e7f0 Code review fixes from #478 bb97207 Rename Lambda.apply_position a7cb650 Quieten Makefile when runtime dep files are not present c656dc9 Merge flambda-backend changes 11b5424 Avoid printing double spaces in function argument lists 7751faa Restore locations to Typedtree.{pat,let}_bound_idents_full e450b6c add build_ocaml_compiler.sexp 0403bb3 Revert PR 9895 to continue installing VERSION b3447db Ensure new local attributes are namespaced properly 7f213fc Allow empty functions again 8f22ad8 Bugfix: ensure local domain state is initialised 80f54dd Bugfix for Selectgen with regions e8133a1 Fix external-external signature inclusion 9840051 Bootstrap d879f23 Merge remote-tracking branch 'jane/local-reviewed' into local-merge 94454f5 Use Local_store for the local allocations ref 54a164c Create fewer regions, according to typechecking (#59) 1c2479b Merge flambda-backend changes ce34678 Fix printing of modes in return types 91f2281 Hook mode variable solving into Btype.snapshot/backtrack 54e4b09 Move Alloc_mode and Value_mode to Btype ff4611e Merge flambda-backend changes ce62e45 Ensure allocations are initialised, even dead ones 6b6ec5a Fix the alloc.ml test on 32-bit builds 81e9879 Merge flambda-backend changes 40a7f89 Update repo URL for ocaml-jst, and rename script. 0454ee7 Add some new locally-allocating primitives (#57) 8acdda1 Reset the local stack pointer in exception handlers (#56) 8dafa98 Improve typing for (||) and (&&) (#55) 8c64754 Fix make_check_all_arches (#54) b50cd45 Allow arguments to primitives to be local even in tail position (#53) cad125d Fix modes from or-patterns (#50) 4efdb72 Fix tailcalls tests with inlining (#52) 4a795cb Flambda support (#49) 74722cb Add [@ocaml.principal] and [@ocaml.noprincipal] attributes, and use in oo.mli 6d7d3b8 Ensure that functions are evaluated after their arguments (flambda-backend #353) 89bda6b Keep Sys.opaque_identity in Cmm and Mach (port upstream PR 9412) a39126a Fix tailcalls within regions (#48) 4ac4cfd Fix stdlib manpages build 3a95f5e Merge flambda-backend changes efe80c9 Add jane/pull-flambda-patches script fca94c4 Register allocations for Omitted parameter closures (#47) 103b139 Remove various FIXMEs (#46) 62ba2c1 Bootstrap a0062ad Allow local allocations for various primitives (#43) 7a2165e Allow primitives to be poly-moded (#43) 2af3f55 Fix a flaky test by refactoring TypePairs (ocaml/ocaml#10638) 58dd807 Bootstrap ee3be10 Fix modes in build_apply for partial applications fe73656 Tweak for evaluation order of labelled partial applications (#10653) 0527570 Fix caml_modify on local allocations (#40) e657e99 Relax modes for `as` patterns (#42) f815bf2 Add special mode handling for tuples in matches and let bindings (#38) 39f1211 Only take the upper bounds of modes associated with allocations (#37) aec6fde Interpret arrow types in "local positions" differently c4f3319 Bootstrap ff6fdad Add some missing regions 40d586d Bootstrap 66d8110 Switch to a system with 3 modes for values f2c5a85 Bugfix for Comballoc with local allocations. (#41) 83bcd09 Fix bug with root scanning during compaction (#39) 1b5ec83 Track modes in Lambda.lfunction and onwards (#33) f1e2e97 Port ocaml/ocaml#10728 56703cd Port ocaml/ocaml#10081 eb66785 Support local allocations in i386 and fix amd64 bug (#31) c936b19 Disallow local recursive non-functions (#30) c7a193a GC support for local allocations (#29) 8dd7270 Nonlocal fields (#28) e19a2f0 Bootstrap 694b9ac Add syntax to the parser for local allocations (#26) f183008 Lower initial stack size 918226f Allow local closure allocations (#27) 2552e7d Introduce mode variables (#25) bc41c99 Minor fixes for local allocations (#24) a2a4e60 Runtime and compiler support for more local allocations (#23) d030554 Typechecking for local allocations (#21) 9ee2332 Bugfix missing from #20 02c4cef Retain block-structured local regions until Mach. 86dbe1c amd64: Move stack realloc calls out-of-line 324d218 More typing modes and locking of environments a4080b8 Initial version of local allocation (unsafe) git-subtree-dir: ocaml git-subtree-split: 173842c
This PR adds support for local allocations to the middle-end, following on from #478.
The main change is a change to Lambda to introduce the following features, as well as the corresponding middle-end changes to compile them:
The last of these is the trickiest: tail calls from within a region should end the region after the arguments to the tail call have been evaluated, but before control is transferred.
I'm afraid that the middle-end changes are large and complicated. However, the complicated bit (handling overapplications and tail calls of local closures) is not large, and the large bit (plumbing alloc modes through every single allocating primitive) is not complicated. (There are detailed tests, but not in this PR as they depend also on frontend support)
This PR only adds support for Closure and Flambda1. PR #490 has a draft by @mshinwell of Flambda2 support, but in this PR there is only stub support in Flambda2.
The remaining changes to ocaml/ are the minimal ones required for CI. Full support for local allocs in the ocaml/ subtree will appear later.
(As with #478, this code is extracted from the local allocs branch, whose dev history and previous PRs are here)