- Dec 14, 2020
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Ben Gamari authored
During the compilation of programs GHC very frequently deals with the `Type` type, which is a synonym of `TYPE 'LiftedRep`. This patch teaches GHC to avoid expanding the `Type` synonym (and other nullary type synonyms) during type comparisons, saving a good amount of work. This optimisation is described in `Note [Comparing nullary type synonyms]`. To maximize the impact of this optimisation, we introduce a few special-cases to reduce `TYPE 'LiftedRep` to `Type`. See `Note [Prefer Type over TYPE 'LiftedPtrRep]`. Closes #17958. Metric Decrease: T18698b T1969 T12227 T12545 T12707 T14683 T3064 T5631 T5642 T9020 T9630 T9872a T13035 haddock.Cabal haddock.base
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Andreas Klebinger authoredThe naive way of putting out n characters of indent would be something like `hPutStr hdl (replicate n ' ')`. However this is quite inefficient as we allocate an absurd number of strings consisting of simply spaces as we don't cache them. To improve on this we now track if we can simply write ascii spaces via hPutBuf instead. This is the case when running with -ddump-to-file where we force the encoding to be UTF8. This avoids both the cost of going through encoding as well as avoiding allocation churn from all the white space. Instead we simply use hPutBuf on a preallocated unlifted string. When dumping stg like this: > nofib/spectral/simple/Main.hs -fforce-recomp -ddump-stg-final -ddump-to-file -c +RTS -s Allocations went from 1,778 MB to 1,702MB. About a 4% reduction of allocation! I did not measure the difference in runtime but expect it to be similar. Bumps the haddock submodule since the interface of GHC's Pretty slightly changed. ------------------------- Metric Decrease: T12227 ------------------------- -
Sylvain Henry authored
The unit database cache, the home unit and the unit state were stored in DynFlags while they ought to be stored in the compiler session state (HscEnv). This patch fixes this. It introduces a new UnitEnv type that should be used in the future to handle separate unit environments (especially host vs target units). Related to #17957 Bump haddock submodule
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Ben Gamari authored
This was inadvertently merged. This reverts commit 7e9debd4.
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Ben Gamari authored
During the compilation of programs GHC very frequently deals with the `Type` type, which is a synonym of `TYPE 'LiftedRep`. This patch teaches GHC to avoid expanding the `Type` synonym (and other nullary type synonyms) during type comparisons, saving a good amount of work. This optimisation is described in `Note [Comparing nullary type synonyms]`. To maximize the impact of this optimisation, we introduce a few special-cases to reduce `TYPE 'LiftedRep` to `Type`. See `Note [Prefer Type over TYPE 'LiftedPtrRep]`. Closes #17958. Metric Decrease: T18698b T1969 T12227 T12545 T12707 T14683 T3064 T5631 T5642 T9020 T9630 T9872a T13035 haddock.Cabal haddock.base
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The haddock submodule is also updated so that it understands the changes to patterns.
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- Dec 13, 2020
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- Dec 12, 2020
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adam authored
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Both sub-demands encode the same information. This is a trivial change and already affects a few regression tests (e.g. `T5075`), so no separate regression test is necessary.
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It's useful to annotate a non-exported top-level function like `g` in ```hs module Lib (h) where g :: Int -> Int -> (Int,Int) g m 1 = (m, 0) g m n = (2 * m, 2 `div` n) {-# NOINLINE g #-} h :: Int -> Int h 1 = 0 h m | odd m = snd (g m 2) | otherwise = uncurry (+) (g 2 m) ``` with its demand `UCU(CS(P(1P(U),SP(U))`, which tells us that whenever `g` was called, the second component of the returned pair was evaluated strictly. Since #18903 we do so for local functions, where we can see all calls. For top-level functions, we can assume that all *exported* functions are demanded according to `topDmd` and thus get sound demands for non-exported top-level functions. The demand on `g` is crucial information for Nested CPR, which may the go on and unbox `g` for the second pair component. That is true even if that pair component may diverge, as is the case for the call site `g 13 0`, which throws a div-by-zero exception. In `T18894b`, you can even see the new demand annotation enabling us to eta-expand a function that we wouldn't be able to eta-expand without Call Arity. We only track bindings of function type in order not to risk huge compile-time regressions, see `isInterestingTopLevelFn`. There was a CoreLint check that rejected strict demand annotations on recursive or top-level bindings, which seems completely unjustified. All the cases I investigated were fine, so I removed it. Fixes #18894. -
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Move code unrelated to runtime evaluation out of GHC.Runtime.Eval
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Fix parsing of "libffi-3.3.tar.gz". NB: switch to a newer libffi isn't done in this patch
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Consider the following code: proc (C x y) -> ... Before this patch, the evidence binding for the Arrow dictionary was attached to the C pattern: proc (C x y) { $dArrow = ... } -> ... But then when we desugar this, we use arrow operations ("arr", ">>>"...) specialised for this arrow: let arr_xy = arr $dArrow -- <-- Not in scope! ... in arr_xy (\(C x y) { $dArrow = ... } -> ...) This patch allows arrow operations to be type-checked before the proc itself, avoiding this issue. Fix #17423 -
This Note has severely bitrotted, as it has no references anywhere in the codebase, and none of the functions that it mentions exist anymore. Let's just delete this. While I was in town, I deleted some outdated comments from `checkFamPatBinders` of a similar caliber. Fixes #19008. [ci skip]
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- Dec 11, 2020
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Tests that the output of the `:doc` command is correct for duplicate record fields defined using -XDuplicateRecordFields.
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Do not print `<has no documentation>` alongside a valid doc. Additionally, if two matching symbols lack documentation then the message will only be printed once. Hence, `<has no documentation>` will be printed at most once and only if all matching symbols are lacking docs.
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It looks like I neglected to update this after introduce flavour transformers.
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Also refactor the job definition to eliminate the bug by construction.
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Every time I am asked about how to interpret these events I need to figure it out from scratch. It's well past time that the users guide properly documents these.
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Fixes errors introduced by 3a55b3a2.
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- Dec 10, 2020
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The change fixes build failure on musl: ``` rts/linker/Elf.c:2031:3: error: warning: implicit declaration of function 'dlclose'; did you mean 'close'? [-Wimplicit-function-declaration] 2031 | dlclose(nc->dlopen_handle); | ^~~~~~~ | close ``` Signed-off-by:Sergei Trofimovich <slyfox@gentoo.org>
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Be more clear on what this optimisation being on by default means in terms of yields.
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“Yield points enabled” is confusing (and probably wrong? I am not 100% sure what it means). Change it to a simple “on”. Undo this change from 2c23fff2.
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- Dec 09, 2020
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This should fix #19002.
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Optimization either returns Nothing if nothing is to be done or `Just <cmmExpr>` otherwise. There is no point in being lazy in `cmmExpr`. We usually inspect this element so the thunk gets forced not long after. We might eliminate it as dead code once in a blue moon but that's not a case worth optimizing for. Overall the impact of this is rather low. As Cmm.Opt doesn't allocate much (compared to the rest of GHC) to begin with.
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Sinking requires us to track live local regs after each cmm statement. We used to do this via "Set LocalReg". However we can replace this with a solution based on IntSet which is overall more efficient without losing much. The thing we lose is width of the variables, which isn't used by the sinking pass anyway. I also reworked how we keep assignments to regs mentioned in skipped assignments. I put the details into Note [Keeping assignemnts mentioned in skipped RHSs]. The gist of it is instead of keeping track of it via the use count which is a `IntMap Int` we now use the live regs set (IntSet) which is quite a bit faster. I think it also matches the semantics a lot better. The skipped (not discarded) assignment does in fact keep the regs on it's rhs alive so keeping track of this in the live set seems like the clearer solution as well. Improves allocations for T3294 by yet another 1%.
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About 0.6% reduction in allocations for the code I was looking at. Not a huge difference but no need to throw away performance.
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Helps avoid allocating the folding function. Improves perf for T3294 by about 1%.
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Reduces allocation for the test case I was looking at by about 1.2%. Mostly from avoiding allocation of some folding functions which turn into let-no-escape bindings which just reuse their environment instead. We also force inlining in a few key places in CmmSink which helps a bit more.
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- Dec 08, 2020
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This patch fixes several aspects of kind inference for data type declarations, especially data /instance/ declarations Specifically 1. In kcConDecls/kcConDecl make it clear that the tc_res_kind argument is only used in the H98 case; and in that case there is no result kind signature; and hence no need for the disgusting splitPiTys in kcConDecls (now thankfully gone). The GADT case is a bit different to before, and much nicer. This is what fixes #18891. See Note [kcConDecls: kind-checking data type decls] 2. Do not look at the constructor decls of a data/newtype instance in tcDataFamInstanceHeader. See GHC.Tc.TyCl.Instance Note [Kind inference for data family instances]. This was a new realisation that arose when doing (1) This causes a few knock-on effects in the tests suite, because we require more information than before in the instance /header/. New user-manual material about this in "Kind inference in data type declarations" and "Kind inference for data/newtype instance declarations". 3. Minor improvement in kcTyClDecl, combining GADT and H98 cases 4. Fix #14111 and #8707 by allowing the header of a data instance to affect kind inferece for the the data constructor signatures; as described at length in Note [GADT return types] in GHC.Tc.TyCl This led to a modest refactoring of the arguments (and argument order) of tcConDecl/tcConDecls. 5. Fix #19000 by inverting the sense of the test in new_locs in GHC.Tc.Solver.Canonical.canDecomposableTyConAppOK.
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- Dec 05, 2020
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