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12793 commits behind the upstream repository.

Re-engineer the binder-swap transformation

Simon Peyton Jones authored 5 years ago

The binder-swap transformation is implemented by the occurrence
analyser -- see Note [Binder swap] in OccurAnal. However it had
a very nasty corner in it, for the case where the case scrutinee
was a GlobalId.  This led to trouble and hacks, and ultimately
to #16296.

This patch re-engineers how the occurrence analyser implements
the binder-swap, by actually carrying out a substitution rather
than by adding a let-binding.  It's all described in
Note [The binder-swap substitution].

I did a few other things along the way

* Fix a bug in StgCse, which could allow a loop breaker to be CSE'd
  away.  See Note [Care with loop breakers] in StgCse.  I think it can
  only show up if occurrence analyser sets up bad loop breakers, but
  still.

* Better commenting in SimplUtils.prepareAlts

* A little refactoring in CoreUnfold; nothing significant
  e.g. rename CoreUnfold.mkTopUnfolding to mkFinalUnfolding

* Renamed CoreSyn.isFragileUnfolding to hasCoreUnfolding

* Move mkRuleInfo to CoreFVs

We observed respectively 4.6% and 5.9% allocation decreases for the following
tests:

Metric Decrease:
    T9961
    haddock.base

b943b25d

b943b25d 5 years ago

Name	Last commit	Last update
.gitlab
bindisttest
compiler
distrib
docs
driver
ghc
hadrian
includes
libffi
libraries
mk
rts
rules
testsuite
utils
libffi-tarballs @ 14c0d0ca
nofib @ cef118de
.appveyor.sh
.ghcid
.gitattributes
.gitignore
.gitlab-ci.yml
.gitmodules
.mailmap
.travis.yml
CODEOWNERS
HACKING.md
INSTALL.md
LICENSE
MAKEHELP.md
Makefile
README.md
Vagrantfile
aclocal.m4
appveyor.yml
boot
config.guess
config.sub
configure.ac
ghc.mk
hie.yaml
install-sh
llvm-passes
llvm-targets
packages
validate

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