[Git][ghc/ghc][wip/T18185] 35 commits: IdInfo: Add reference to bitfield-packing ticket

Ryan Scott gitlab at gitlab.haskell.org
Thu May 21 17:09:31 UTC 2020 


Ryan Scott pushed to branch wip/T18185 at Glasgow Haskell Compiler / GHC


Commits:
e9c0110c by Ben Gamari at 2020-05-14T12:25:53-04:00
IdInfo: Add reference to bitfield-packing ticket

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9bd20e83 by Sebastian Graf at 2020-05-15T10:42:09-04:00
DmdAnal: Improve handling of precise exceptions

This patch does two things: Fix possible unsoundness in what was called
the "IO hack" and implement part 2.1 of the "fixing precise exceptions"
plan in
https://gitlab.haskell.org/ghc/ghc/wikis/fixing-precise-exceptions,
which, in combination with !2956, supersedes !3014 and !2525.

**IO hack**

The "IO hack" (which is a fallback to preserve precise exceptions
semantics and thus soundness, rather than some smart thing that
increases precision) is called `exprMayThrowPreciseException` now.
I came up with two testcases exemplifying possible unsoundness (if
twisted enough) in the old approach:

- `T13380d`: Demonstrating unsoundness of the "IO hack" when resorting
             to manual state token threading and direct use of primops.
             More details below.
- `T13380e`: Demonstrating unsoundness of the "IO hack" when we have
             Nested CPR. Not currently relevant, as we don't have Nested
             CPR yet.
- `T13380f`: Demonstrating unsoundness of the "IO hack" for safe FFI
             calls.

Basically, the IO hack assumed that precise exceptions can only be
thrown from a case scrutinee of type `(# State# RealWorld, _ #)`. I
couldn't come up with a program using the `IO` abstraction that violates
this assumption. But it's easy to do so via manual state token threading
and direct use of primops, see `T13380d`. Also similar code might be
generated by Nested CPR in the (hopefully not too) distant future, see
`T13380e`. Hence, we now have a more careful test in `forcesRealWorld`
that passes `T13380{d,e}` (and will hopefully be robust to Nested CPR).

**Precise exceptions**

In #13380 and #17676 we saw that we didn't preserve precise exception
semantics in demand analysis. We fixed that with minimal changes in
!2956, but that was terribly unprincipled.

That unprincipledness resulted in a loss of precision, which is tracked
by these new test cases:

- `T13380b`: Regression in dead code elimination, because !2956 was too
             syntactic about `raiseIO#`
- `T13380c`: No need to apply the "IO hack" when the IO action may not
             throw a precise exception (and the existing IO hack doesn't
             detect that)

Fixing both issues in !3014 turned out to be too complicated and had
the potential to regress in the future. Hence we decided to only fix
`T13380b` and augment the `Divergence` lattice with a new middle-layer
element, `ExnOrDiv`, which means either `Diverges` (, throws an
imprecise exception) or throws a *precise* exception.

See the wiki page on Step 2.1 for more implementational details:
https://gitlab.haskell.org/ghc/ghc/wikis/fixing-precise-exceptions#dead-code-elimination-for-raiseio-with-isdeadenddiv-introducing-exnordiv-step-21

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568d7279 by Ben Gamari at 2020-05-15T10:42:46-04:00
GHC.Cmm.Opt: Handle MO_XX_Conv

This MachOp was introduced by 2c959a1894311e59cd2fd469c1967491c1e488f3
but a wildcard match in cmmMachOpFoldM hid the fact that it wasn't
handled. Ideally we would eliminate the match but this appears to be a
larger task.

Fixes #18141.

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5bcf8606 by Ryan Scott at 2020-05-17T08:46:38-04:00
Remove duplicate Note [When to print foralls] in GHC.Core.TyCo.Ppr

There are two different Notes named `[When to print foralls]`. The
most up-to-date one is in `GHC.Iface.Type`, but there is a second
one in `GHC.Core.TyCo.Ppr`. The latter is less up-to-date, as it was
written before GHC switched over to using ifaces to pretty-print
types. I decided to just remove the latter and replace it with a
reference to the former.

[ci skip]

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55f0e783 by Fumiaki Kinoshita at 2020-05-21T12:10:44-04:00
base: Add Generic instances to various datatypes under GHC.*

* GHC.Fingerprint.Types: Fingerprint
* GHC.RTS.Flags: GiveGCStats, GCFlags, ConcFlags, DebugFlags, CCFlags, DoHeapProfile, ProfFlags, DoTrace, TraceFlags, TickyFlags, ParFlags and RTSFlags
* GHC.Stats: RTSStats and GCStats
* GHC.ByteOrder: ByteOrder
* GHC.Unicode: GeneralCategory
* GHC.Stack.Types: SrcLoc

Metric Increase:
    haddock.base

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a9311cd5 by Gert-Jan Bottu at 2020-05-21T12:11:31-04:00
Explicit Specificity

Implementation for Ticket #16393.
Explicit specificity allows users to manually create inferred type variables,
by marking them with braces.
This way, the user determines which variables can be instantiated through
visible type application.

The additional syntax is included in the parser, allowing users to write
braces in type variable binders (type signatures, data constructors etc).
This information is passed along through the renamer and verified in the
type checker.
The AST for type variable binders, data constructors, pattern synonyms,
partial signatures and Template Haskell has been updated to include the
specificity of type variables.

Minor notes:
- Bumps haddock submodule
- Disables pattern match checking in GHC.Iface.Type with GHC 8.8

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24e61aad by Ben Price at 2020-05-21T12:12:17-04:00
Lint should say when it is checking a rule

It is rather confusing that when lint finds an error in a rule attached
to a binder, it reports the error as in the RHS, not the rule:
  ...
  In the RHS of foo

We add a clarifying line:
  ...
  In the RHS of foo
  In a rule attached to foo

The implication that the rule lives inside the RHS is a bit odd, but
this niggle is already present for unfoldings, whose pattern we are
following.

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78c6523c by Ben Gamari at 2020-05-21T12:13:01-04:00
nonmoving: Optimise the write barrier

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13f6c9d0 by Andreas Klebinger at 2020-05-21T12:13:45-04:00
Refactor linear reg alloc to remember past assignments.

When assigning registers we now first try registers we
assigned to in the past, instead of picking the "first"
one.

This is in extremely helpful when dealing with loops for
which variables are dead for part of the loop.

This is important for patterns like this:

        foo = arg1
    loop:
        use(foo)
        ...
        foo = getVal()
        goto loop;

There we:
* assign foo to the register of arg1.
* use foo, it's dead after this use as it's overwritten after.
* do other things.
* look for a register to put foo in.

If we pick an arbitrary one it might differ from the register the
start of the loop expect's foo to be in.
To fix this we simply look for past register assignments for
the given variable. If we find one and the register is free we
use that register.

This reduces the need for fixup blocks which match the register
assignment between blocks. In the example above between the end
and the head of the loop.

This patch also moves branch weight estimation ahead of register
allocation and adds a flag to control it (cmm-static-pred).
* It means the linear allocator is more likely to assign the hotter
  code paths first.
* If it assign these first we are:
  + Less likely to spill on the hot path.
  + Less likely to introduce fixup blocks on the hot path.

These two measure combined are surprisingly effective. Based on nofib
we get in the mean:

* -0.9% instructions executed
* -0.1% reads/writes
* -0.2% code size.
* -0.1% compiler allocations.
* -0.9% compile time.
* -0.8% runtime.

Most of the benefits are simply a result of removing redundant moves
and spills.

Reduced compiler allocations likely are the result of less code being
generated. (The added lookup is mostly non-allocating).

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edc2cc58 by Andreas Klebinger at 2020-05-21T12:14:25-04:00
NCG: Codelayout: Distinguish conditional and other branches.

In #18053 we ended up with a suboptimal code layout because
the code layout algorithm didn't distinguish between conditional
and unconditional control flow.

We can completely eliminate unconditional control flow instructions
by placing blocks next to each other, not so much for conditionals.

In terms of implementation we simply give conditional branches less
weight before computing the layout.

Fixes #18053

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b7a6b2f4 by Gleb Popov at 2020-05-21T12:15:26-04:00
gitlab-ci: Set locale to C.UTF-8.

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a8c27cf6 by Stefan Holdermans at 2020-05-21T12:16:08-04:00
Allow spaces in GHCi :script file names

This patch updates the user interface of GHCi so that file names passed
to the ':script' command may contain spaces escaped with a backslash.

For example:

  :script foo\ bar.script

The implementation uses a modified version of 'words' that does not
break on escaped spaces.

Fixes #18027.

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82663959 by Stefan Holdermans at 2020-05-21T12:16:08-04:00
Add extra tests for GHCi :script syntax checks

The syntax for GHCi's ":script" command allows for only a single file
name to be passed as an argument. This patch adds a test for the cases
in which a file name is missing or multiple file names are passed.

Related to #T18027.

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a0b79e1b by Stefan Holdermans at 2020-05-21T12:16:08-04:00
Allow GHCi :script file names in double quotes

This patch updates the user interface of GHCi so that file names passed
to the ':script' command can be wrapped in double quotes.

For example:

  :script "foo bar.script"

The implementation uses a modified version of 'words' that treats
character sequences enclosed in double quotes as single words.

Fixes #18027.

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cf566330 by Stefan Holdermans at 2020-05-21T12:16:08-04:00
Update documentation for GHCi :script

This patch adds the fixes that allow for file names containing spaces to
be passed to GHCi's ':script' command to the release notes for 8.12 and
expands the user-guide documentation for ':script' by mentioning how
such file names can be passed.

Related to #18027.

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0004ccb8 by Tuan Le at 2020-05-21T12:16:46-04:00
llvmGen: Consider Relocatable read-only data as not constantReferences: #18137

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964d3ea2 by John Ericson at 2020-05-21T12:17:30-04:00
Use `Checker` for `tc_pat`

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b797aa42 by John Ericson at 2020-05-21T12:17:30-04:00
Use `Checker` for `tc_lpat` and `tc_lpats`

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5108e84a by John Ericson at 2020-05-21T12:17:30-04:00
More judiciously panic in `ts_pat`

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510e0451 by John Ericson at 2020-05-21T12:17:30-04:00
Put `PatEnv` first in `GHC.Tc.Gen.Pat.Checker`

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cb4231db by John Ericson at 2020-05-21T12:17:30-04:00
Tiny cleaup eta-reduce away a function argument

In GHC, not in the code being compiled!

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6890c38d by John Ericson at 2020-05-21T12:17:30-04:00
Use braces with do in `SplicePat` case for consistency

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3451584f by buggymcbugfix at 2020-05-21T12:18:06-04:00
Fix spelling mistakes and typos

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b552e531 by buggymcbugfix at 2020-05-21T12:18:06-04:00
Add INLINABLE pragmas to Enum list producers

The INLINABLE pragmas ensure that we export stable (unoptimised) unfoldings in
the interface file so we can do list fusion at usage sites.

Related tickets: #15185, #8763, #18178.

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e7480063 by buggymcbugfix at 2020-05-21T12:18:06-04:00
Piggyback on Enum Word methods for Word64

If we are on a 64 bit platform, we can use the efficient Enum Word
methods for the Enum Word64 instance.

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892b0c41 by buggymcbugfix at 2020-05-21T12:18:06-04:00
Document INLINE(ABLE) pragmas that enable fusion

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2b363ebb by Richard Eisenberg at 2020-05-21T12:18:45-04:00
MR template should ask for key part
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a95bbd0b by Sebastian Graf at 2020-05-21T12:19:37-04:00
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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d3d055b8 by Galen Huntington at 2020-05-21T12:20:18-04:00
Clarify pitfalls of NegativeLiterals; see #18022.
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1b508a9e by Alexey Kuleshevich at 2020-05-21T12:21:02-04:00
Fix wording in primops documentation to reflect the correct reasoning:

* Besides resizing functions, shrinking ones also mutate the
  size of a mutable array and because of those two `sizeofMutabeByteArray`
  and `sizeofSmallMutableArray` are now deprecated
* Change reference in documentation to the newer functions `getSizeof*`
  instead of `sizeof*` for shrinking functions
* Fix incorrect mention of "byte" instead of "small"

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4ca0c8a1 by Andreas Klebinger at 2020-05-21T12:21:53-04:00
Don't variable-length encode magic iface constant.

We changed to use variable length encodings for many types by default,
including Word32. This makes sense for numbers but not when Word32 is
meant to represent four bytes.

I added a FixedLengthEncoding newtype to Binary who's instances
interpret their argument as a collection of bytes instead of a number.

We then use this when writing/reading magic numbers to the iface file.

I also took the libery to remove the dummy iface field.

This fixes #18180.

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a1275081 by Krzysztof Gogolewski at 2020-05-21T12:22:35-04:00
Add a regression test for #11506

The testcase works now.
See explanation in https://gitlab.haskell.org/ghc/ghc/issues/11506#note_273202

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8a816e5f by Krzysztof Gogolewski at 2020-05-21T12:23:55-04:00
Sort deterministically metric output

Previously, we sorted according to the test name and way,
but the metrics (max_bytes_used/peak_megabytes_allocated etc.)
were appearing in nondeterministic order.

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566cc73f by Sylvain Henry at 2020-05-21T12:24:45-04:00
Move isDynLinkName into GHC.Types.Name

It doesn't belong into GHC.Unit.State

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6ca3d6a6 by Ryan Scott at 2020-05-21T13:08:40-04:00
Add orderingTyCon to wiredInTyCons (#18185)

`Ordering` needs to be wired in for use in the built-in `CmpNat` and
`CmpSymbol` type families, but somehow it was never added to the list
of `wiredInTyCons`, leading to the various oddities observed
in #18185. Easily fixed by moving `orderingTyCon` from
`basicKnownKeyNames` to `wiredInTyCons`.

Fixes #18185.

- - - - -


30 changed files:

- .gitlab-ci.yml
- .gitlab/ci.sh
- .gitlab/merge_request_templates/merge-request.md
- compiler/GHC.hs
- compiler/GHC/Builtin/Names.hs
- compiler/GHC/Builtin/Names/TH.hs
- compiler/GHC/Builtin/Types.hs
- compiler/GHC/Builtin/primops.txt.pp
- compiler/GHC/Cmm.hs
- compiler/GHC/Cmm/CLabel.hs
- compiler/GHC/Cmm/Opt.hs
- compiler/GHC/CmmToAsm.hs
- compiler/GHC/CmmToAsm/BlockLayout.hs
- compiler/GHC/CmmToAsm/CFG.hs
- compiler/GHC/CmmToAsm/Instr.hs
- compiler/GHC/CmmToAsm/Reg/Linear.hs
- compiler/GHC/CmmToAsm/Reg/Linear/Base.hs
- compiler/GHC/CmmToAsm/Reg/Linear/PPC.hs
- compiler/GHC/CmmToAsm/Reg/Linear/SPARC.hs
- compiler/GHC/CmmToAsm/Reg/Linear/State.hs
- compiler/GHC/CmmToAsm/Reg/Linear/X86.hs
- compiler/GHC/CmmToAsm/Reg/Linear/X86_64.hs
- compiler/GHC/CmmToC.hs
- compiler/GHC/CmmToLlvm/Data.hs
- compiler/GHC/Core/Arity.hs
- compiler/GHC/Core/Coercion.hs
- compiler/GHC/Core/ConLike.hs
- compiler/GHC/Core/DataCon.hs
- compiler/GHC/Core/DataCon.hs-boot
- compiler/GHC/Core/Lint.hs


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