This is an attempt to use the by-products of nested cpr analysis.

by giving it the meaning: "Assuming my first argument is terminating,
then I am terminating".

In pictures: This is the lattice, which is not a simple product lattice any more:

       ------ <L><L>------
     /          | \       \
    /           | <L><L>t  \
<S><L>          |           <S><L>
 |  \ \         |           |  |  \
 |   \ <S><L>t  |          /   |   <S><L>t
 |    \         |         /    |
 \     \        |        /     |
  \     ----- <S><S>-----      |
   \           |    \          |
    \          |     <S><S>t   /
     \         |              /
      ---------⊥-------------/

This means that we need to be careful when lub’ing: If one branch is lazy, but
not absent in an argument or free variable, and the other branch is strict,
then even if both branches claim to terminate, we need to remove the
termination flag (as one had the termination under a stronger hypothesis as the
hole result) (Feels inelegant.)

There is no unit for lubDmdType any more. So for case, use we use botDmdType
for no alternatives, and foldr1 if there are multiple.

Unlifted variables (e.g. Int#) are tricky. Everything is strict in them, so for
an *unlifted* argument, <L>t implies <S>t and hence <S>t ⊔ <L>t = <S>t, and we
really want to make use of that stronger equation. But when lub’ing, we don’t
know any more if this is the demand for an unlifted type. So instead, the
demand type of x :: Int# itself is {x ↦ <L>} t, while x :: Int continues to
have type {x ↦ <S>} t.

It is important that functions (including primitive operations and constructors
like I#) have a strict demand on their unlifted argument. But it turned out to
be easier to enforce this in the demand analyser: So even if f claims to have a
lazy demand on a argument of unlifted type, we make this demand strict before
feeding it into the argument.

because this is the right-identity to `bothDmdResult`, and this is the
right thing to do in a lazy context.

to detect definite convergence (required for nested CPR).

by only passing the demand on the free variables, and whether the
argument (resp. scrunitee) may or will diverge.

Make different postProcess code paths for function arguments (which are
post-processed just to be both'ed) and unsaturated functions (which are
post-processed for other reasons.)

its first argument is just used for its length (the arity of the call).
So changing the type to Int to reflect that.

Also add a note [Demands from unsaturated function calls] that hopefully
comprehensively and comprehensibly explains what is going on here.

this is a small-step-refactoring patch and not very interesting on its
own.

by adding Notes and using easier to understand combinators.

Simon Peyton Jones authored 11 years ago and Joachim Breitner committed 11 years ago

Joachim and I are committing this onto a branch so that we can share it,
but we expect to do a bit more work before merging it onto head.

Nofib staus:
  - Most programs, no change
  - A few improve
  - A couple get worse (cacheprof, tak, rfib)
Investigating the "get worse" set is what's holding up putting this
on head.

The major issue is this.  Consider

    map (f g) ys

where f's demand signature looks like

   f :: <L,C1(C1(U))> -> <L,U> -> .

So 'f' is not saturated.  What demand do we place on g?
Answer
        C(C1(U))
That is, the inner C1 should stay, even though f is not saturated.

I found that this made a significant difference in the demand signatures
inferred in GHC.IO, which uses lots of higher-order exception handlers.

I also had to add used-once demand signatures for some of the
'catch' primops, so that we know their handlers are only called once.

Simon Peyton Jones authored 11 years ago and Joachim Breitner committed 11 years ago

This patch was authored by SPJ and extracted from "Improve the handling
of used-once stuff" by Joachim.

Simon Peyton Jones authored 11 years ago and Joachim Breitner committed 11 years ago

This patch was authored by SPJ, and extracted from "Improve the handling
of used-once stuff" by Joachim.

Simon Peyton Jones authored 11 years ago and Joachim Breitner committed 11 years ago

This is authored by SPJ, and split out out "Improve the handling of
used-once stuff" by Joachim.

Simon Peyton Jones authored 11 years ago and Joachim Breitner committed 11 years ago

This was authored by SPJ and extracted from the "Improve the handling of
used-once stuff" patch by Joachim.

This is a long-standing bug.  We were generating a Given
equality between kind variables, and (at least until we support
kind coercions) we can't do that.

The fix is to drop such Given equalities entirely. That may
mean we can't prove some things, but that's fair enough -- the
current proof language can't express such proofs.

See Note [Do not create Given kind equalities] in TcSMonad

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>

because it is not a top deman (see previous commit), and it is only used
in an argument to mkStrictSig.

because topDmdType is ''not'' the top of the lattice, as it puts an
implicit absent demand on free variables, but Abs is the bottom of the
Usage lattice.

Why nopDmdType? Becuase it is the demand of doing nothing: Everything
lazy, everything absent, no definite divergence.

but do forget about certain divergence, if required. Fixes one part of
ticket #8598.

The added function (deferAfterIO) can maybe be merged with existing
code, but given the ongoing work in the nested-cpr branch, I defer that
work.

The existing flag -ddump-stranal dumps the full Core, which is very
verbose and not always helpful. This adds a more concise output (one
line per top-level bind) that is faster to read, and especially more
suitable to be used when writing test cases for the strictness analiser.

On win64 sizeof(long) != sizeof(void*), so debugTrace was casting a
value of incorrect size causing a validate failure.

Signed-off-by: Austin Seipp <austin@well-typed.com>

After commit 55c703b8, this code is no longer used anywhere.

This improves the output of `git shortlog` and others, see

  http://git-scm.com/docs/git-shortlog



for more details.

The mapping is in part derived from the Darcs author-spelling file
which was removed some time ago via 47a01802.

There's still a couple of unmapped `<unknown>` authors in the Git history which will
be hopefully mapped in the future as well to provide complete authorship information
throughout all of GHC's recorded development history.

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>

The lexer now uses unicode single quotation marks in its error messages
if possible.  This is due to the use of the 'quotes' combinator.

Helps fix #7396

This was an egregious error.  If e :: T (Q ty1)
then when we have the splice

     $e :: ty2

we must ensure that ty1~ty2 before we even think about
running the splice!

I took the opportunity to remove the dead-code tcSpliceDecls
altogether.

Signed-off-by: Austin Seipp <austin@well-typed.com>

Signed-off-by: Austin Seipp <austin@well-typed.com>

Signed-off-by: Austin Seipp <austin@well-typed.com>