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| author | Ben Gamari <ben@smart-cactus.org> | 2022-03-11 13:48:05 -0500 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2022-05-17 16:00:14 -0400 |
| commit | b048a9f4e28186d2245427d2d83f08418573fae5 (patch) | |
| tree | e9b7e97ed8ede18bb65c512645620bb460260842 /rts/sm | |
| parent | cb52b4ae1508639e2686717d220b977e201394d3 (diff) | |
| download | haskell-b048a9f4e28186d2245427d2d83f08418573fae5.tar.gz | |
codeGen: Ensure that static datacon apps are included in SRTs
When generating an SRT for a recursive group, GHC.Cmm.Info.Build.oneSRT
filters out recursive references, as described in Note [recursive SRTs].
However, doing so for static functions would be unsound, for the reason
described in Note [Invalid optimisation: shortcutting].
However, the same argument applies to static data constructor
applications, as we discovered in #20959. Fix this by ensuring that
static data constructor applications are included in recursive SRTs.
The approach here is not entirely satisfactory, but it is a starting
point.
Fixes #20959.
Diffstat (limited to 'rts/sm')
| -rw-r--r-- | rts/sm/Storage.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/rts/sm/Storage.h b/rts/sm/Storage.h index 00f2943a51..0fecc50208 100644 --- a/rts/sm/Storage.h +++ b/rts/sm/Storage.h @@ -147,6 +147,12 @@ void move_STACK (StgStack *src, StgStack *dest); bits = link_field & 3; if ((bits | prev_static_flag) != 3) { ... } + However, this mechanism for tracking liveness has an important implication: + once a static object becomes unreachable it must never become reachable again. + One would think that this can by definition never happen but in the past SRT + generation bugs have caused precisely this behavior with disasterous results. + See Note [No static object resurrection] in GHC.Cmm.Info.Build for details. + -------------------------------------------------------------------------- */ #define STATIC_BITS 3 |