diff options
| author | Ömer Sinan Ağacan <omeragacan@gmail.com> | 2018-10-10 10:07:05 +0300 |
|---|---|---|
| committer | Ömer Sinan Ağacan <omeragacan@gmail.com> | 2018-10-10 10:07:21 +0300 |
| commit | ac977688523e5d77eb6f041f043552410b0c21da (patch) | |
| tree | d77cb46adac639d002489f7c2432852a9a506a22 /compiler/prelude/PrelRules.hs | |
| parent | d728c3c578cc9e9205def2c1e96934487b364b7b (diff) | |
| download | haskell-ac977688523e5d77eb6f041f043552410b0c21da.tar.gz | |
Fix dataToTag# argument evaluation
See #15696 for more details. We now always enter dataToTag# argument (done in
generated Cmm, in StgCmmExpr). Any high-level optimisations on dataToTag#
applications are done by the simplifier. Looking at tag bits (instead of
reading the info table) for small types is left to another diff.
Incorrect test T14626 is removed. We no longer do this optimisation (see
comment:44, comment:45, comment:60).
Comments and notes about special cases around dataToTag# are removed. We no
longer have any special cases around it in Core.
Other changes related to evaluating primops (seq# and dataToTag#) will be
pursued in follow-up diffs.
Test Plan: Validates with three regression tests
Reviewers: simonpj, simonmar, hvr, bgamari, dfeuer
Reviewed By: simonmar
Subscribers: rwbarton, carter
GHC Trac Issues: #15696
Differential Revision: https://phabricator.haskell.org/D5201
Diffstat (limited to 'compiler/prelude/PrelRules.hs')
| -rw-r--r-- | compiler/prelude/PrelRules.hs | 13 |
1 files changed, 0 insertions, 13 deletions
diff --git a/compiler/prelude/PrelRules.hs b/compiler/prelude/PrelRules.hs index e94490007f..28c0628f16 100644 --- a/compiler/prelude/PrelRules.hs +++ b/compiler/prelude/PrelRules.hs @@ -1030,19 +1030,6 @@ dataToTagRule = a `mplus` b guard $ ty1 `eqType` ty2 return tag - -- Why don't we simplify tagToEnum# (dataToTag# x) to x? We would - -- like to, but it seems tricky. See #14282. The trouble is that - -- we never actually see tagToEnum# (dataToTag# x). Because dataToTag# - -- is can_fail, this expression is immediately transformed into - -- - -- case dataToTag# @T x of wild - -- { __DEFAULT -> tagToEnum# @T wild } - -- - -- and wild has no unfolding. Simon Peyton Jones speculates one way around - -- might be to arrange to give unfoldings to case binders of CONLIKE - -- applications and mark dataToTag# CONLIKE, but he doubts it's really - -- worth the trouble. - -- dataToTag (K e1 e2) ==> tag-of K -- This also works (via exprIsConApp_maybe) for -- dataToTag x |