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<h3 style="margin-top: 20px; margin-bottom: 10px;">
Rodrigo Mesquita pushed to branch wip/romes/rts-linker-direct-symbol-lookup at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
</h3>
<h4 style="margin-top: 10px; margin-bottom: 10px;">
Commits:
</h4>
<ul>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/19883a23b8bc704118fa663d8bab00a503b5a527">19883a23</a></strong>
<div>
<span> by Alan Zimmerman </span> <i> at 2024-04-05T16:58:17-04:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","Menlo","DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>EPA: Use EpaLocation for RecFieldsDotDot
So we can update it to a delta position in makeDeltaAst if needed.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e8724327d995a67d3eb066dfe4f9ee03e64dd6b5">e8724327</a></strong>
<div>
<span> by Matthew Pickering </span> <i> at 2024-04-05T16:58:53-04:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","Menlo","DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Remove accidentally committed test.hs
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/88cb3e1079e88ba10065ce260a96095ae96d58e8">88cb3e10</a></strong>
<div>
<span> by Fendor </span> <i> at 2024-04-08T09:03:34-04:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","Menlo","DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Avoid UArray when indexing is not required
`UnlinkedBCO`'s can occur many times in the heap. Each `UnlinkedBCO`
references two `UArray`'s but never indexes them. They are only needed
to encode the elements into a `ByteArray#`. The three words for
the lower bound, upper bound and number of elements are essentially
unused, thus we replace `UArray` with a wrapper around `ByteArray#`.
This saves us up to three words for each `UnlinkedBCO`.
Further, to avoid re-allocating these words for `ResolvedBCO`, we repeat
the procedure for `ResolvedBCO` and add custom `Binary` and `Show` instances.
For example, agda's repl session has around 360_000 UnlinkedBCO's,
so avoiding these three words is already saving us around 8MB residency.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/f2cc1107790d42fee1a11d5b16bc282d31ea6f78">f2cc1107</a></strong>
<div>
<span> by Fendor </span> <i> at 2024-04-08T09:04:11-04:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","Menlo","DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Never UNPACK `FastMutInt` for counting z-encoded `FastString`s
In `FastStringTable`, we count the number of z-encoded FastStrings
that exist in a GHC session.
We used to UNPACK the counters to not waste memory, but live retainer
analysis showed that we allocate a lot of `FastMutInt`s, retained by
`mkFastZString`.
We lazily compute the `FastZString`, only incrementing the counter when the `FastZString` is
forced.
The function `mkFastStringWith` calls `mkZFastString` and boxes the
`FastMutInt`, leading to the following core:
mkFastStringWith
= \ mk_fs _ ->
= case stringTable of
{ FastStringTable _ n_zencs segments# _ ->
...
case ((mk_fs (I# ...) (FastMutInt n_zencs))
`cast` <Co:2> :: ...)
...
Marking this field as `NOUNPACK` avoids this reboxing, eliminating the
allocation of a fresh `FastMutInt` on every `FastString` allocation.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e2688e0c7a92497b249d60fa128979347311cc49">e2688e0c</a></strong>
<div>
<span> by Rodrigo Mesquita </span> <i> at 2024-04-08T16:41:09+01:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","Menlo","DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>rts: free error message before returning
Fixes a memory leak in rts/linker/PEi386.c
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0ad72f29077cb39ecf903f9ce9e809ca1cc6e3b7">0ad72f29</a></strong>
<div>
<span> by Alexis King </span> <i> at 2024-04-08T16:42:10+01:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","Menlo","DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>linker: Avoid linear search when looking up Haskell symbols via dlsym
See the primary Note [Looking up symbols in the relevant objects] for a
more in-depth explanation.
When dynamically loading a Haskell symbol (typical when running a splice or
GHCi expression), before this commit we would search for the symbol in
all dynamic libraries that were loaded. However, this could be very
inefficient when too many packages are loaded (which can happen if there are
many package dependencies) because the time to lookup the would be
linear in the number of packages loaded.
This commit drastically improves symbol loading performance by
introducing a mapping from units to the handles of corresponding loaded
dlls. These handles are returned by dlopen when we load a dll, and can
then be used to look up in a specific dynamic library.
Looking up a given Name is now much more precise because we can get
lookup its unit in the mapping and lookup the symbol solely in the
handles of the dynamic libraries loaded for that unit.
In one measurement, the wait time before the expression was executed
went from +-38 seconds down to +-2s.
This commit also includes Note [Symbols may not be found in pkgs_loaded],
explaining the fallback to the old behaviour in case no dll can be found
in the unit mapping for a given Name.
Fixes #23415
Co-authored-by: Rodrigo Mesquita (@alt-romes)
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/aa6a1201d4188c25adb9283d4a9736a112fb5189">aa6a1201</a></strong>
<div>
<span> by Rodrigo Mesquita </span> <i> at 2024-04-08T16:42:11+01:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","Menlo","DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>rts: Make addDLL a wrapper around loadNativeObj
Rewrite the implementation of `addDLL` as a wrapper around the more
principled `loadNativeObj` rts linker function. The latter should be
preferred while the former is preserved for backwards compatibility.
`loadNativeObj` was previously only available on ELF platforms, so this
commit further refactors the rts linker to transform loadNativeObj_ELF
into loadNativeObj_POSIX, which is available in ELF and MachO platforms.
The refactor made it possible to remove the `dl_mutex` mutex in favour
of always using `linker_mutex` (rather than a combination of both).
Lastly, we implement `loadNativeObj` for Windows too.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/51593f5801a145b58ae72db4f5d398931b068793">51593f58</a></strong>
<div>
<span> by Rodrigo Mesquita </span> <i> at 2024-04-08T16:42:11+01:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","Menlo","DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Use symbol cache in internal interpreter too
This commit makes the symbol cache that was used by the external
interpreter available for the internal interpreter too.
This follows from the analysis in #23415 that suggests the internal
interpreter could benefit from this cache too, and that there is no good
reason not to have the cache for it too. It also makes it a bit more
uniform to have the symbol cache range over both the internal and
external interpreter.
This commit also refactors the cache into a function which is used by
both `lookupSymbol` and also by `lookupSymbolInDLL`, extending the
caching logic to `lookupSymbolInDLL` too.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0e12f612d7b3890b075324d4e847c28ab7449663">0e12f612</a></strong>
<div>
<span> by Ben Gamari </span> <i> at 2024-04-08T16:42:11+01:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","Menlo","DejaVu Sans Mono","Liberation Mono","Consolas","Ubuntu Mono","Courier New","andale mono","lucida console",monospace; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>testsuite: Add test for lookupSymbolInNativeObj
</pre>
</li>
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<h4 style="margin-top: 10px; margin-bottom: 10px;">
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compiler/GHC.hs
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The diff was not included because it is too large.
</h5>
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