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| author | Andreas Klebinger <klebinger.andreas@gmx.at> | 2018-03-13 13:54:53 -0400 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2018-03-13 13:57:17 -0400 |
| commit | adc3415f14aa090c54c68149dcb1d99f19132a83 (patch) | |
| tree | ff40375cbd41de0d0087c73cea3de15f3843d592 /docs | |
| parent | abfe10487d2dba49bf511297f14575f9089cc5b1 (diff) | |
| download | haskell-wip/D4327.tar.gz | |
WIP: Add likelyhood to alternatives from stg onwardswip/D4327
Summary:
Adds a Freq value to Stg/Cmm cases/switches/conditionals.
Currently only generates these values by checking alternatives for
bottom expressions.
They are passed along to the backend where they affect conditional generation
slightly.
As it stands runtime improvements seem to be less than expected. This might only be worth merging once we have more branch weights available.
Reviewers: hvr, goldfire, bgamari, simonmar, simonpj, erikd
Reviewed By: simonpj
Subscribers: simonpj, rwbarton, thomie, carter
GHC Trac Issues: #14672
Differential Revision: https://phabricator.haskell.org/D4327
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/debugging.rst | 9 | ||||
| -rw-r--r-- | docs/users_guide/using-optimisation.rst | 18 |
2 files changed, 25 insertions, 2 deletions
diff --git a/docs/users_guide/debugging.rst b/docs/users_guide/debugging.rst index cf926348a0..d11cc04fd0 100644 --- a/docs/users_guide/debugging.rst +++ b/docs/users_guide/debugging.rst @@ -612,7 +612,7 @@ are doing, not all of it will be useful. Use these flags to suppress the parts that you are not interested in. .. ghc-flag:: -dsuppress-all - :shortdesc: In core dumps, suppress everything (except for uniques) that is + :shortdesc: In dumps, suppress everything (except for uniques) that is suppressible. :type: dynamic @@ -663,6 +663,13 @@ parts that you are not interested in. Suppress the printing of module qualification prefixes. This is the ``Data.List`` in ``Data.List.length``. +.. ghc-flag:: -dsuppress-timestamps + :shortdesc: Suppress timestamps in dumps + :type: dynamic + + Suppress the printing of timestamps. + This makes it easier to diff dumps. + .. ghc-flag:: -dsuppress-type-signatures :shortdesc: Suppress type signatures :type: dynamic diff --git a/docs/users_guide/using-optimisation.rst b/docs/users_guide/using-optimisation.rst index 3566462eeb..e0251d3454 100644 --- a/docs/users_guide/using-optimisation.rst +++ b/docs/users_guide/using-optimisation.rst @@ -45,7 +45,7 @@ optimisation to be performed, which can have an impact on how much of your program needs to be recompiled when you change something. This is one reason to stick to no-optimisation when developing code. -**No ``-O*``-type option specified:** This is taken to mean “Please +**No ``-O*``-type option specified:** This is taken to mean “Please compile quickly; I'm not over-bothered about compiled-code quality.” So, for example, ``ghc -c Foo.hs`` @@ -666,6 +666,22 @@ by saying ``-fno-wombat``. a case expression, which is good for performance, but bad if you are using ``seq`` on partial applications. +.. ghc-flag:: -funlikely-bottoms + :shortdesc: Marks bottom expressions as unlikely in the backend. + Implied by :ghc-flag:`-O`. + :type: dynamic + :reverse: -fno-unlikely-bottoms + :category: + + :default: off + + This information is used by some backends to generate faster code by + taking the hot path into account. + + It recognizes functions like `error`, `undefined` and some functions + which are guaranteed to raise an exception. This includes the generated + failure branch on incomplete pattern matches. + .. ghc-flag:: -fregs-graph :shortdesc: Use the graph colouring register allocator for register allocation in the native code generator. Implied by :ghc-flag:`-O2`. |