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<h3>
Sebastian Graf pushed to branch wip/mod-rem-strict
at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
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<h4>
Commits:
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<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/748cf6be65805844ce0c5a978b457feefd6d06bd">748cf6be</a></strong>
<div>
<span>by Sebastian Graf</span>
<i>at 2020-05-14T18:37:21+02:00</i>
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<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Make `Int`'s `mod` and `rem` strict in their first arguments
They used to be strict until 4d2ac2d (9 years ago).
It's obviously better to be strict for performance reasons.
It also blocks #18067.
NoFib results:
```
--------------------------------------------------------------------------------
Program Allocs Instrs
--------------------------------------------------------------------------------
integer -1.1% +0.4%
wheel-sieve2 +21.2% +20.7%
--------------------------------------------------------------------------------
Min -1.1% -0.0%
Max +21.2% +20.7%
Geometric Mean +0.2% +0.2%
```
The regression in `wheel-sieve2` is due to reboxing that likely will go
away with the resolution of #18067. See !3282 for details.
Fixes #18187.
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<h4>1 changed file:</h4>
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<a href="#13051caa3e90fdf52d8cd971a61ab47ad07c105f">
libraries/base/GHC/Real.hs
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<h4>Changes:</h4>
<li id="13051caa3e90fdf52d8cd971a61ab47ad07c105f">
<a href="https://gitlab.haskell.org/ghc/ghc/-/commit/748cf6be65805844ce0c5a978b457feefd6d06bd#13051caa3e90fdf52d8cd971a61ab47ad07c105f"><strong>libraries/base/GHC/Real.hs</strong></a>
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<td class="line_content match " style="padding-left: 0.5em; padding-right: 0.5em; color: rgba(0,0,0,0.3);" bgcolor="#fafafa">@@ -334,7 +334,7 @@ instance Integral Int where</td>
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<pre style="margin: 0;"> <span id="LC334" class="line" lang="haskell"> <span class="c1" style="color: #998; font-style: italic;">-- in GHC.Int</span></span>
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<pre style="margin: 0;"> <span id="LC335" class="line" lang="haskell"> <span class="o" style="font-weight: 600;">|</span> <span class="n" style="color: #333;">otherwise</span> <span class="o" style="font-weight: 600;">=</span> <span class="n" style="color: #333;">a</span> <span class="p">`</span><span class="n" style="color: #333;">quotInt</span><span class="p">`</span> <span class="n" style="color: #333;">b</span></span>
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<pre style="margin: 0;"> <span id="LC336" class="line" lang="haskell"></span>
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<pre style="margin: 0;">-<span id="LC337" class="line" lang="haskell"> <span class="n" style="color: #333;">a</span> <span class="p">`</span><span class="n" style="color: #333;">rem</span><span class="p">`</span> <span class="n" style="color: #333;">b</span></span>
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<pre style="margin: 0;">+<span id="LC337" class="line" lang="haskell"> <span class="o" style="font-weight: 600;"><span class="idiff left right">!</span></span><span class="n" style="color: #333;">a</span> <span class="p">`</span><span class="n" style="color: #333;">rem</span><span class="p">`</span> <span class="n" style="color: #333;">b</span></span>
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<pre style="margin: 0;"> <span id="LC338" class="line" lang="haskell"> <span class="o" style="font-weight: 600;">|</span> <span class="n" style="color: #333;">b</span> <span class="o" style="font-weight: 600;">==</span> <span class="mi" style="color: #099;">0</span> <span class="o" style="font-weight: 600;">=</span> <span class="n" style="color: #333;">divZeroError</span></span>
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<pre style="margin: 0;"> <span id="LC339" class="line" lang="haskell"> <span class="c1" style="color: #998; font-style: italic;">-- The quotRem CPU instruction fails for minBound `quotRem` -1,</span></span>
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<pre style="margin: 0;"> <span id="LC340" class="line" lang="haskell"> <span class="c1" style="color: #998; font-style: italic;">-- but minBound `rem` -1 is well-defined (0). We therefore</span></span>
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<td class="line_content match " style="padding-left: 0.5em; padding-right: 0.5em; color: rgba(0,0,0,0.3);" bgcolor="#fafafa">@@ -348,7 +348,7 @@ instance Integral Int where</td>
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<pre style="margin: 0;"> <span id="LC348" class="line" lang="haskell"> <span class="c1" style="color: #998; font-style: italic;">-- in GHC.Int</span></span>
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<pre style="margin: 0;"> <span id="LC349" class="line" lang="haskell"> <span class="o" style="font-weight: 600;">|</span> <span class="n" style="color: #333;">otherwise</span> <span class="o" style="font-weight: 600;">=</span> <span class="n" style="color: #333;">a</span> <span class="p">`</span><span class="n" style="color: #333;">divInt</span><span class="p">`</span> <span class="n" style="color: #333;">b</span></span>
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<pre style="margin: 0;"> <span id="LC350" class="line" lang="haskell"></span>
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<pre style="margin: 0;">-<span id="LC351" class="line" lang="haskell"> <span class="n" style="color: #333;">a</span> <span class="p">`</span><span class="n" style="color: #333;">mod</span><span class="p">`</span> <span class="n" style="color: #333;">b</span></span>
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<pre style="margin: 0;">+<span id="LC351" class="line" lang="haskell"> <span class="o" style="font-weight: 600;"><span class="idiff left right">!</span></span><span class="n" style="color: #333;">a</span> <span class="p">`</span><span class="n" style="color: #333;">mod</span><span class="p">`</span> <span class="n" style="color: #333;">b</span></span>
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<pre style="margin: 0;"> <span id="LC352" class="line" lang="haskell"> <span class="o" style="font-weight: 600;">|</span> <span class="n" style="color: #333;">b</span> <span class="o" style="font-weight: 600;">==</span> <span class="mi" style="color: #099;">0</span> <span class="o" style="font-weight: 600;">=</span> <span class="n" style="color: #333;">divZeroError</span></span>
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<pre style="margin: 0;"> <span id="LC353" class="line" lang="haskell"> <span class="c1" style="color: #998; font-style: italic;">-- The divMod CPU instruction fails for minBound `divMod` -1,</span></span>
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<pre style="margin: 0;"> <span id="LC354" class="line" lang="haskell"> <span class="c1" style="color: #998; font-style: italic;">-- but minBound `mod` -1 is well-defined (0). We therefore</span></span>
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