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Hannes Siebenhandl pushed to branch wip/mpickering-hannes at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
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Commits:
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/de963147f76ee311e0a888f212e347f7c9bf8713">de963147</a></strong>
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<span> by Fendor </span> <i> at 2024-03-27T15:02:52+01:00 </i>
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<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 GHC.
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.
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1 changed file:
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<a href="#d51029aec6ce58e66d4b48865c1dd0d2038fda29">
compiler/GHC/Data/FastString.hs
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Changes:
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<li id="d51029aec6ce58e66d4b48865c1dd0d2038fda29">
<a href="https://gitlab.haskell.org/ghc/ghc/-/commit/de963147f76ee311e0a888f212e347f7c9bf8713#d51029aec6ce58e66d4b48865c1dd0d2038fda29"><strong style="font-weight: bold;">compiler/GHC/Data/FastString.hs</strong></a>
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<td class="diff-line-num unfold js-unfold old_line" data-linenumber="308" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">...</td>
<td class="diff-line-num unfold js-unfold new_line" data-linenumber="308" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">...</td>
<td class="line_content match" style="color: rgba(31,30,36,0.24); padding: inherit;" bgcolor="#fbfafd">@@ -308,7 +308,7 @@ See Note [Updating the FastString table] on how it's updated.</td>
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<td class="old_line diff-line-num" data-linenumber="308" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
308
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<td class="new_line diff-line-num" data-linenumber="308" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
308
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<td class="line_content" style="padding: inherit;"><pre style='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: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;'> <span id="LC308" class="line" lang="haskell"><span class="cm" style="color: #998; font-style: italic;">-}</span></span>
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<td class="old_line diff-line-num" data-linenumber="309" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
309
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<td class="new_line diff-line-num" data-linenumber="309" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
309
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<td class="line_content" style="padding: inherit;"><pre style='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: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;'> <span id="LC309" class="line" lang="haskell"><span class="kr" style="font-weight: 600;">data</span> <span class="kt" style="color: #458; font-weight: 600;">FastStringTable</span> <span class="o" style="font-weight: 600;">=</span> <span class="kt" style="color: #458; font-weight: 600;">FastStringTable</span></span>
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<td class="old_line diff-line-num" data-linenumber="310" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
310
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<td class="new_line diff-line-num" data-linenumber="310" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
310
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<td class="line_content" style="padding: inherit;"><pre style='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: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;'> <span id="LC310" class="line" lang="haskell"> <span class="cp" style="color: #999; font-weight: 600;">{-# UNPACK #-}</span> <span class="o" style="font-weight: 600;">!</span><span class="kt" style="color: #458; font-weight: 600;">FastMutInt</span> <span class="c1" style="color: #998; font-style: italic;">-- the unique ID counter shared with all buckets</span></span>
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<td class="old_line diff-line-num old" data-linenumber="311" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
311
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<td class="new_line diff-line-num old" data-linenumber="311" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #fac5cd; border-right-style: solid; padding: inherit;" align="right" bgcolor="#f9d7dc">
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<td class="line_content old" style="padding: inherit;" bgcolor="#fbe9eb"><pre style='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: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;'>-<span id="LC311" class="line" lang="haskell"> <span class="cp" style="color: #999; font-weight: 600;">{-# UNPACK #-}</span> <span class="o" style="font-weight: 600;">!</span><span class="kt" style="color: #458; font-weight: 600;">FastMutInt</span> <span class="c1" style="color: #998; font-style: italic;">-- number of computed z-encodings for all buckets</span></span>
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<td class="old_line diff-line-num new" data-linenumber="312" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="new_line diff-line-num new" data-linenumber="311" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
311
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style='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: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;'>+<span id="LC311" class="line" lang="haskell"> <span class="cp" style="color: #999; font-weight: 600;">{-# <span class="idiff left right addition" style="background-color: #c7f0d2;">NO</span>UNPACK #-}</span> <span class="o" style="font-weight: 600;">!</span><span class="kt" style="color: #458; font-weight: 600;">FastMutInt</span> <span class="c1" style="color: #998; font-style: italic;">-- number of computed z-encodings for all buckets</span></span>
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<td class="old_line diff-line-num" data-linenumber="312" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
312
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<td class="new_line diff-line-num" data-linenumber="312" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
312
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<td class="line_content" style="padding: inherit;"><pre style='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: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;'> <span id="LC312" class="line" lang="haskell"> <span class="p">(</span><span class="kt" style="color: #458; font-weight: 600;">Array</span><span class="o" style="font-weight: 600;">#</span> <span class="p">(</span><span class="kt" style="color: #458; font-weight: 600;">IORef</span> <span class="kt" style="color: #458; font-weight: 600;">FastStringTableSegment</span><span class="p">))</span> <span class="c1" style="color: #998; font-style: italic;">-- concurrent segments</span></span>
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<td class="old_line diff-line-num" data-linenumber="313" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
313
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<td class="new_line diff-line-num" data-linenumber="313" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
313
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<td class="line_content" style="padding: inherit;"><pre style='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: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;'> <span id="LC313" class="line" lang="haskell"></span>
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<td class="old_line diff-line-num" data-linenumber="314" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
314
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<td class="new_line diff-line-num" data-linenumber="314" style="width: 35px; color: rgba(31,30,36,0.24); border-right-width: 1px; border-right-color: #ececef; border-right-style: solid; padding: inherit;" align="right" bgcolor="#fbfafd">
314
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<td class="line_content" style="padding: inherit;"><pre style='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: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;'> <span id="LC314" class="line" lang="haskell"><span class="kr" style="font-weight: 600;">data</span> <span class="kt" style="color: #458; font-weight: 600;">FastStringTableSegment</span> <span class="o" style="font-weight: 600;">=</span> <span class="kt" style="color: #458; font-weight: 600;">FastStringTableSegment</span></span>
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