- Nov 15, 2020
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The use of `tcSplitForAllTyVars` in `tcDataFamInstHeader` was the immediate cause of #18939, and replacing it with a new `tcSplitForAllInvisTyVars` function (which behaves like `tcSplitForAllTyVars` but only splits invisible type variables) fixes the issue. However, this led me to realize that _most_ uses of `tcSplitForAllTyVars` in GHC really ought to be `tcSplitForAllInvisTyVars` instead. While I was in town, I opted to replace most uses of `tcSplitForAllTys` with `tcSplitForAllTysInvis` to reduce the likelihood of such bugs in the future. I say "most uses" above since there is one notable place where we _do_ want to use `tcSplitForAllTyVars`: in `GHC.Tc.Validity.forAllTyErr`, which produces the "`Illegal polymorphic type`" error message if you try to use a higher-rank `forall` without having `RankNTypes` enabled. Here, we really do want to split all `forall`s, not just invisible ones, or we run the risk of giving an inaccurate error message in the newly added `T18939_Fail` test case. I debated at some length whether I wanted to name the new function `tcSplitForAllInvisTyVars` or `tcSplitForAllTyVarsInvisible`, but in the end, I decided that I liked the former better. For consistency's sake, I opted to rename the existing `splitPiTysInvisible` and `splitPiTysInvisibleN` functions to `splitInvisPiTys` and `splitPiTysInvisN`, respectively, so that they use the same naming convention. As a consequence, this ended up requiring a `haddock` submodule bump. Fixes #18939.
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There is a zoo of `splitForAll-` functions in `GHC.Core.Type` (as well as `tcSplitForAll-` functions in `GHC.Tc.Utils.TcType`) that all do very similar things, but vary in the particular form of type variable that they return. To make things worse, the names of these functions are often quite misleading. Some particularly egregious examples: * `splitForAllTys` returns `TyCoVar`s, but `splitSomeForAllTys` returns `VarBndr`s. * `splitSomeForAllTys` returns `VarBndr`s, but `tcSplitSomeForAllTys` returns `TyVar`s. * `splitForAllTys` returns `TyCoVar`s, but `splitForAllTysInvis` returns `InvisTVBinder`s. (This in particular arose in the context of #18939, and this finally motivated me to bite the bullet and improve the status quo vis-à-vis how we name these functions.) In an attempt to bring some sanity to how these functions are named, I have opted to rename most of these functions en masse to use consistent suffixes that describe the particular form of type variable that each function returns. In concrete terms, this amounts to: * Functions that return a `TyVar` now use the suffix `-TyVar`. This caused the following functions to be renamed: * `splitTyVarForAllTys` -> `splitForAllTyVars` * `splitForAllTy_ty_maybe` -> `splitForAllTyVar_maybe` * `tcSplitForAllTys` -> `tcSplitForAllTyVars` * `tcSplitSomeForAllTys` -> `tcSplitSomeForAllTyVars` * Functions that return a `CoVar` now use the suffix `-CoVar`. This caused the following functions to be renamed: * `splitForAllTy_co_maybe` -> `splitForAllCoVar_maybe` * Functions that return a `TyCoVar` now use the suffix `-TyCoVar`. This caused the following functions to be renamed: * `splitForAllTy` -> `splitForAllTyCoVar` * `splitForAllTys` -> `splitForAllTyCoVars` * `splitForAllTys'` -> `splitForAllTyCoVars'` * `splitForAllTy_maybe` -> `splitForAllTyCoVar_maybe` * Functions that return a `VarBndr` now use the suffix corresponding to the most relevant type synonym. This caused the following functions to be renamed: * `splitForAllVarBndrs` -> `splitForAllTyCoVarBinders` * `splitForAllTysInvis` -> `splitForAllInvisTVBinders` * `splitForAllTysReq` -> `splitForAllReqTVBinders` * `splitSomeForAllTys` -> `splitSomeForAllTyCoVarBndrs` * `tcSplitForAllVarBndrs` -> `tcSplitForAllTyVarBinders` * `tcSplitForAllTysInvis` -> `tcSplitForAllInvisTVBinders` * `tcSplitForAllTysReq` -> `tcSplitForAllReqTVBinders` * `tcSplitForAllTy_maybe` -> `tcSplitForAllTyVarBinder_maybe` Note that I left the following functions alone: * Functions that split apart things besides `ForAllTy`s, such as `splitFunTys` or `splitPiTys`. Thankfully, there are far fewer of these functions than there are functions that split apart `ForAllTy`s, so there isn't much of a pressing need to apply the new naming convention elsewhere. * Functions that split apart `ForAllCo`s in `Coercion`s, such as `GHC.Core.Coercion.splitForAllCo_maybe`. We could theoretically apply the new naming convention here, but then we'd have to figure out how to disambiguate `Type`-splitting functions from `Coercion`-splitting functions. Ultimately, the `Coercion`-splitting functions aren't used nearly as much as the `Type`-splitting functions, so I decided to leave the former alone. This is purely refactoring and should cause no change in behavior.
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Standard debugging tools don't know how to understand these so let's not produce them unless asked.
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Previously the `.debug_aranges` and `.debug_info` (DIE) DWARF information would claim that procedures (represented with a `DW_TAG_subprogram` DIE) would only span the range covered by their entry block. This omitted all of the continuation blocks (represented by `DW_TAG_lexical_block` DIEs), confusing `perf`. Fix this by introducing a end-of-procedure label and using this as the `DW_AT_high_pc` of procedure `DW_TAG_subprogram` DIEs Fixes #17605.
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- Nov 13, 2020
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These are used to find the current roots of the garbage collector. Co-authored-by:
Sven Tennie's avatarSven Tennie <sven.tennie@gmail.com> Co-authored-by:
Matthew Pickering's avatarMatthew Pickering <matthewtpickering@gmail.com> Co-authored-by:
default avatarBen Gamari <bgamari.foss@gmail.com>
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See Note [Exciting arity] why we emit the warning at all and why we only do after the second iteration now. Fixes #18937.
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As we found out in #18870, `andArityType` is not monotone, with potentially severe consequences for termination of fixed-point iteration. That showed in an abundance of "Exciting arity" DEBUG messages that are emitted whenever we do more than one step in fixed-point iteration. The solution necessitates also recording `OneShotInfo` info for `ABot` arity type. Thus we get the following definition for `ArityType`: ``` data ArityType = AT [OneShotInfo] Divergence ``` The majority of changes in this patch are the result of refactoring use sites of `ArityType` to match the new definition. The regression test `T18870` asserts that we indeed don't emit any DEBUG output anymore for a function where we previously would have. Similarly, there's a regression test `T18937` for #18937, which we expect to be broken for now. Fixes #18870.
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- Nov 12, 2020
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Ben Gamari authored
In ticket #18733 we noticed a rather serious deficiency in the current fingerprinting logic for recursive groups. I have described the old fingerprinting story and its problems in Note [Fingerprinting recursive groups] and have reworked the story accordingly to avoid these issues. Fixes #18733.
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Ben Gamari authored
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- Nov 11, 2020
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This uses the highMemDynamic flag introduced earlier to verify that dynamic objects are properly unloaded.
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(This change is originally written by niteria) This adds two functions: * `loadNativeObj` * `unloadNativeObj` and implements them for Linux. They are useful if you want to load a shared object with Haskell code using the system linker and have GHC call dlclose() after the code is no longer referenced from the heap. Using the system linker allows you to load the shared object above outside the low-mem region. It also loads the DWARF sections in a way that `perf` understands. `dl_iterate_phdr` is what makes this implementation Linux specific.
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Fixes #16525 by tracking dependencies between object file symbols and marking symbol liveness during garbage collection See Note [Object unloading] in CheckUnload.c for details.
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This seems like a reasonable default as the object file size increases by around 5%.
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It turns out that some important native debugging/profiling tools (e.g. perf) rely only on symbol tables for function name resolution (as opposed to using DWARF DIEs). However, previously GHC would emit temporary symbols (e.g. `.La42b`) to identify module-internal entities. Such symbols are dropped during linking and therefore not visible to runtime tools (in addition to having rather un-helpful unique names). For instance, `perf report` would often end up attributing all cost to the libc `frame_dummy` symbol since Haskell code was no covered by any proper symbol (see #17605). We now rather follow the model of C compilers and emit descriptively-named local symbols for module internal things. Since this will increase object file size this behavior can be disabled with the `-fno-expose-internal-symbols` flag. With this `perf record` can finally be used against Haskell executables. Even more, with `-g3` `perf annotate` provides inline source code.
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In various places in the NCG we need the Module currently being compiled. Let's move this into the environment instead of chewing threw another register.
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It appears this was an oversight as there is no reason the full DynFlags is necessary.
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- Nov 10, 2020
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This got fixed sometime recently; not worth it trying to figure out which commit.
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Co-authored-by:
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Previously the overflow check for the IMAGE_REL_AMD64_ADDR32NB relocation failed to account for the signed nature of the value. Specifically, the overflow check was: uint64_t v; v = S + A; if (v >> 32) { ... } However, `v` ultimately needs to fit into 32-bits as a signed value. Consequently, values `v > 2^31` in fact overflow yet this is not caught by the existing overflow check. Here we rewrite the overflow check to rather ensure that `INT32_MIN <= v <= INT32_MAX`. There is now quite a bit of repetition between the `IMAGE_REL_AMD64_REL32` and `IMAGE_REL_AMD64_ADDR32` cases but I am leaving fixing this for future work. This bug was first noticed by @awson. Fixes #15808.
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- Nov 08, 2020
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Ben Gamari authored
The previous merge mistakenly reverted it.
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Ben Gamari authored
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- Nov 06, 2020
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See Note [Racing weak pointer evacuation] for all of the gory details.
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1) Don't modify DynFlags (too much) for -dynamic-too: now when we generate dynamic outputs for "-dynamic-too", we only set "dynamicNow" boolean field in DynFlags instead of modifying several other fields. These fields now have accessors that take dynamicNow into account. 2) Use DynamicTooState ADT to represent -dynamic-too state. It's much clearer than the undocumented "DynamicTooConditional" that was used before. As a result, we can finally remove the hscs_iface_dflags field in HscRecomp. There was a comment on this field saying: "FIXME (osa): I don't understand why this is necessary, but I spent almost two days trying to figure this out and I couldn't .. perhaps someone who understands this code better will remove this later." I don't fully understand the details, but it was needed because of the changes made to the DynFlags for -dynamic-too. There is still something very dubious in GHC.Iface.Recomp: we have to disable the "dynamicNow" flag at some point for some Backpack's "heinous hack" to continue to work. It may be because interfaces for indefinite units are always non-dynamic, or because we mix and match dynamic and non-dynamic interfaces (#9176), or something else, who knows?
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This refactors the GHC AST to remove `HsImplicitBndrs` and replace it with `HsOuterTyVarBndrs`, a type which records whether the outermost quantification in a type is explicit (i.e., with an outermost, invisible `forall`) or implicit. As a result of this refactoring, it is now evident in the AST where the `forall`-or-nothing rule applies: it's all the places that use `HsOuterTyVarBndrs`. See the revamped `Note [forall-or-nothing rule]` in `GHC.Hs.Type` (previously in `GHC.Rename.HsType`). Moreover, the places where `ScopedTypeVariables` brings lexically scoped type variables into scope are a subset of the places that adhere to the `forall`-or-nothing rule, so this also makes places that interact with `ScopedTypeVariables` easier to find. See the revamped `Note [Lexically scoped type variables]` in `GHC.Hs.Type` (previously in `GHC.Tc.Gen.Sig`). `HsOuterTyVarBndrs` are used in type signatures (see `HsOuterSigTyVarBndrs`) and type family equations (see `HsOuterFamEqnTyVarBndrs`). The main difference between the former and the latter is that the former cares about specificity but the latter does not. There are a number of knock-on consequences: * There is now a dedicated `HsSigType` type, which is the combination of `HsOuterSigTyVarBndrs` and `HsType`. `LHsSigType` is now an alias for an `XRec` of `HsSigType`. * Working out the details led us to a substantial refactoring of the handling of explicit (user-written) and implicit type-variable bindings in `GHC.Tc.Gen.HsType`. Instead of a confusing family of higher order functions, we now have a local data type, `SkolemInfo`, that controls how these binders are kind-checked. It remains very fiddly, not fully satisfying. But it's better than it was. Fixes #16762. Bumps the Haddock submodule. Co-authored-by:
Simon Peyton Jones <simonpj@microsoft.com> Co-authored-by:
Richard Eisenberg <rae@richarde.dev> Co-authored-by:
Zubin Duggal <zubin@cmi.ac.in>
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- Nov 05, 2020
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The atomic Exchange and CAS operations on integral types are updated to take and return more natural `Word#` rather than `Int#` values. These are bit-block not arithmetic operations, and the sign bit plays no special role. Standardises the names to `atomic<OpType><ValType>Addr#`, where `OpType` is one of `Cas` or `Exchange` and `ValType` is presently either `Word` or `Addr`. Eventually, variants for `Word32` and `Word64` can and should be added, once #11953 and related issues (e.g. #13825) are resolved. Adds tests for `Addr#` CAS that mirror existing tests for `MutableByteArray#`.
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- Nov 04, 2020
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We can now supply additional package dbs to the testsuite. For make the package db can be supplied by passing PACKAGE_DB=/path/to/db. In the testsuite driver it's passed via the --test-package-db argument.
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We no compare these by doing 64bit subtraction and checking the resulting flags. We used to do this differently but the old approach was broken when the high bits compared equal and the comparison was one of >= or <=. The new approach should be both correct and faster.
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- Nov 03, 2020
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bignat_add was a loopbreaker with an INLINE pragma (spotted by @mpickering). This patch makes it non recursive to avoid the issue.
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Constant-folding rules for integerToWord/integerToInt were performing the following coercions at compilation time: integerToWord: target's Integer -> ghc's Word -> target's Word integerToInt : target's Integer -> ghc's Int -> target's Int 1) It was wrong for cross-compilers when GHC's word size is smaller than the target one. This patch avoids passing through GHC's word-sized types: integerToWord: target's Integer -> ghc's Integer -> target's Word integerToInt : target's Integer -> ghc's Integer -> target's Int 2) Additionally we didn't wrap the target word/int literal to make it fit into the target's range! This broke the invariant of literals only containing values in range. The existing code is wrong only with a 64-bit cross-compiling GHC, targeting a 32-bit platform, and performing constant folding on a literal that doesn't fit in a 32-bit word. If GHC was built with DEBUG, the assertion in GHC.Types.Literal.mkLitWord would fail. Otherwise the bad transformation would go unnoticed. -
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