Emit low-level location information for FDO: use discriminators (2/2) #6
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Coercions only apply to their own domains - that is, a coercion on closures doesn't apply to pairs (which might contain, say, a closure and an int). So we don't want to recurse into types in general when applying coercions. Unfortunately, the situation with closures is ... complicated, as explained in comments.
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5e7dfce331 Merge flambda-backend changes 9f7f2d24a7 Edit script for test merge 1ae71ce59d Review comments (ocaml-flambda#6) 1845365bd0 Layouts version 1 aba629478e Immediacy rework (ocaml-flambda#122) cf4eeefb12 Add no-stack-allocation variant of some tests that print lambda (ocaml-flambda#133) 8f22438aa4 Fully switch over Jane Street Merlin support to `.local-*` (ocaml-flambda#136) 5482a8df7b Remove `Lev_module_definition` from lambda (ocaml-flambda#135) 261e016273 Change modular extensions to produce `AST_desc` types (ocaml-flambda#132) 0760c82c68 Disable module patterns in comprehensions (ocaml-flambda#131) 6acac8024b Add Ctype global state debug printers (ocaml-flambda#130) bc32037f10 Enable support for Jane Street's internal Merlin configuration (ocaml-flambda#64) d1a8d0311b Split out `Clflags.Extension` into a new file, `Language_extension` (ocaml-flambda#125) 435de6d38c Fix bootstrap and add legacy CI (ocaml-flambda#126) 7e5a626e4b Improve the API of language extensions to better support upstream compatibility (and also tooling) (ocaml-flambda#13) c4e17b0b2a Replace var with local for faster mode checking (ocaml-flambda#53) 6d477d8ef1 Merge pull request ocaml-flambda#124 from riaqn/merge-backend d7375333a1 minor fixes after merge f1710d6dc4 Merge flambda-backend changes cc18534f49 Just run make boostrap (ocaml-flambda#123) git-subtree-dir: ocaml git-subtree-split: 5e7dfce331d0e39c695fab9b00e3d2cda7d9ebb4
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Use
discriminatorfield of.locdirectives for the extra debug info when building with FDO, instead of using line numbers in fabricated files. This means we can preserve the source locations (file and line and column) in FDO executables.This PR is on top of #5 and addresses the second problem described in #5.
Some
Linearinstructions don't have any debug info associated with them, because the compiler's support for propagating debug info is incomplete. We need debug info on each Linear instruction to emit FDO locations as discriminators. Following the semantics ofdebug_lineprograms,ocamlfdotool infers the missing debug info from the preceding debug info in the order of the original function layout.To ensure that the inferred debug info does not affect backtraces, in comparison to a build without FDO,
ocamlfdowrites the inferred debug info into [fdo] field of Linear.instruction instead of directly to [dbg] field. This way, the inferred debug info is only used for .loc directives when FDO is enabled.