[Git][ghc/ghc][wip/T21851] 9 commits: Tidy implicit binds

Simon Peyton Jones (@simonpj) gitlab at gitlab.haskell.org
Tue Oct 11 21:01:28 UTC 2022 


Simon Peyton Jones pushed to branch wip/T21851 at Glasgow Haskell Compiler / GHC


Commits:
fbb88740 by Matthew Pickering at 2022-10-11T12:48:45-04:00
Tidy implicit binds

We want to put implicit binds into fat interface files, so the easiest
thing to do seems to be to treat them uniformly with other binders.

- - - - -
e058b138 by Matthew Pickering at 2022-10-11T12:48:45-04:00
Interface Files with Core Definitions

This commit adds three new flags

* -fwrite-if-simplified-core: Writes the whole core program into an interface
  file
* -fbyte-code-and-object-code: Generate both byte code and object code
  when compiling a file
* -fprefer-byte-code: Prefer to use byte-code if it's available when
  running TH splices.

The goal for including the core bindings in an interface file is to be able to restart the compiler pipeline
at the point just after simplification and before code generation. Once compilation is
restarted then code can be created for the byte code backend.
This can significantly speed up
start-times for projects in GHCi. HLS already implements its own version of these extended interface
files for this reason.

Preferring to use byte-code means that we can avoid some potentially
expensive code generation steps (see #21700)

* Producing object code is much slower than producing bytecode, and normally you
  need to compile with `-dynamic-too` to produce code in the static and dynamic way, the
  dynamic way just for Template Haskell execution when using a dynamically linked compiler.

* Linking many large object files, which happens once per splice, can be quite
  expensive compared to linking bytecode.

And you can get GHC to compile the necessary byte code so
`-fprefer-byte-code` has access to it by using
`-fbyte-code-and-object-code`.

Fixes #21067

- - - - -
9789ea8e by Matthew Pickering at 2022-10-11T12:48:45-04:00
Teach -fno-code about -fprefer-byte-code

This patch teachs the code generation logic of -fno-code about
-fprefer-byte-code, so that if we need to generate code for a module
which prefers byte code, then we generate byte code rather than object
code.

We keep track separately which modules need object code and which byte
code and then enable the relevant code generation for each. Typically
the option will be enabled globally so one of these sets should be empty
and we will just turn on byte code or object code generation.

We also fix the bug where we would generate code for a module which
enables Template Haskell despite the fact it was unecessary.

Fixes #22016

- - - - -
caced757 by Simon Peyton Jones at 2022-10-11T12:49:21-04:00
Don't keep exit join points so much

We were religiously keeping exit join points throughout, which
had some bad effects (#21148, #22084).

This MR does two things:

* Arranges that exit join points are inhibited from inlining
  only in /one/ Simplifier pass (right after Exitification).

  See Note [Be selective about not-inlining exit join points]
  in GHC.Core.Opt.Exitify

  It's not a big deal, but it shaves 0.1% off compile times.

* Inline used-once non-recursive join points very aggressively
  Given join j x = rhs in
        joinrec k y = ....j x....

  where this is the only occurrence of `j`, we want to inline `j`.
  (Unless sm_keep_exits is on.)

  See Note [Inline used-once non-recursive join points] in
  GHC.Core.Opt.Simplify.Utils

  This is just a tidy-up really.  It doesn't change allocation, but
  getting rid of a binding is always good.

Very effect on nofib -- some up and down.

- - - - -
284cf387 by Simon Peyton Jones at 2022-10-11T12:49:21-04:00
Make SpecConstr bale out less often

When doing performance debugging on #22084 / !8901, I found that the
algorithm in SpecConstr.decreaseSpecCount was so aggressive that if
there were /more/ specialisations available for an outer function,
that could more or less kill off specialisation for an /inner/
function.  (An example was in nofib/spectral/fibheaps.)

This patch makes it a bit more aggressive, by dividing by 2, rather
than by the number of outer specialisations.

This makes the program bigger, temporarily:

   T19695(normal) ghc/alloc   +11.3% BAD

because we get more specialisation.  But lots of other programs
compile a bit faster and the geometric mean in perf/compiler
is 0.0%.

Metric Increase:
    T19695

- - - - -
66af1399 by Cheng Shao at 2022-10-11T12:49:59-04:00
CmmToC: emit explicit tail calls when the C compiler supports it

Clang 13+ supports annotating a return statement using the musttail
attribute, which guarantees that it lowers to a tail call if compilation
succeeds.

This patch takes advantage of that feature for the unregisterised code
generator. The configure script tests availability of the musttail
attribute, if it's available, the Cmm tail calls will become C tail
calls that avoids the mini interpreter trampoline overhead. Nothing is
affected if the musttail attribute is not supported.

Clang documentation:
https://clang.llvm.org/docs/AttributeReference.html#musttail

- - - - -
7f0decd5 by Matthew Pickering at 2022-10-11T12:50:40-04:00
Don't include BufPos in interface files

Ticket #22162 pointed out that the build directory was leaking into the
ABI hash of a module because the BufPos depended on the location of the
build tree.

BufPos is only used in GHC.Parser.PostProcess.Haddock, and the
information doesn't need to be propagated outside the context of a
module.

Fixes #22162

- - - - -
dce9f320 by Cheng Shao at 2022-10-11T12:51:19-04:00
CLabel: fix isInfoTableLabel

isInfoTableLabel does not take Cmm info table into account. This patch is required for data section layout of wasm32 NCG to work.

- - - - -
7a90f5f7 by Simon Peyton Jones at 2022-10-11T22:01:07+01:00
Fire RULES in the Specialiser

The Specialiser has, for some time, fires class-op RULES in the
specialiser itself: see
   Note [Specialisation modulo dictionary selectors]

This MR beefs it up a bit, so that it fires /all/ RULES in the
specialiser, not just class-op rules.  See
   Note [Fire rules in the specialiser]
The result is a bit more specialisation; see test
   simplCore/should_compile/T21851_2

This pushed me into a bit of refactoring.  I made a new data types
GHC.Core.Rules.RuleEnv, which combines
  - the several source of rules (local, home-package, external)
  - the orphan-module dependencies

in a single record for `getRules` to consult.  That drove a bunch of
follow-on refactoring, including allowing me to remove
cr_visible_orphan_mods from the CoreReader data type.

I moved some of the RuleBase/RuleEnv stuff into GHC.Core.Rule.

- - - - -


30 changed files:

- compiler/GHC/Cmm/CLabel.hs
- compiler/GHC/CmmToAsm/AArch64/Ppr.hs
- compiler/GHC/CmmToAsm/X86/Ppr.hs
- compiler/GHC/Core.hs
- compiler/GHC/Core/InstEnv.hs
- compiler/GHC/Core/Opt/Exitify.hs
- compiler/GHC/Core/Opt/Monad.hs
- compiler/GHC/Core/Opt/Pipeline.hs
- compiler/GHC/Core/Opt/Simplify.hs
- compiler/GHC/Core/Opt/Simplify/Env.hs
- compiler/GHC/Core/Opt/Simplify/Monad.hs
- compiler/GHC/Core/Opt/Simplify/Utils.hs
- compiler/GHC/Core/Opt/SpecConstr.hs
- compiler/GHC/Core/Opt/Specialise.hs
- compiler/GHC/Core/Rules.hs
- compiler/GHC/CoreToIface.hs
- compiler/GHC/Driver/Backpack.hs
- compiler/GHC/Driver/Config/Core/Opt/Simplify.hs
- compiler/GHC/Driver/Flags.hs
- compiler/GHC/Driver/Main.hs
- compiler/GHC/Driver/Make.hs
- compiler/GHC/Driver/Pipeline.hs
- compiler/GHC/Driver/Pipeline/Execute.hs
- compiler/GHC/Driver/Pipeline/Phases.hs
- compiler/GHC/Driver/Session.hs
- compiler/GHC/Iface/Ext/Types.hs
- compiler/GHC/Iface/Load.hs
- compiler/GHC/Iface/Make.hs
- compiler/GHC/Iface/Recomp.hs
- compiler/GHC/Iface/Syntax.hs


The diff was not included because it is too large.


View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b3b1ddd8784556ba6c9a69cca1c80d665b5e991b...7a90f5f76355ab122de705f0a87e40483ea1133f

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View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b3b1ddd8784556ba6c9a69cca1c80d665b5e991b...7a90f5f76355ab122de705f0a87e40483ea1133f
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