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| author | Sebastian Graf <sebastian.graf@kit.edu> | 2021-05-14 12:24:48 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-05-19 23:37:44 -0400 |
| commit | e87b8e108303634af8a7247037d50ab10456c189 (patch) | |
| tree | 5a04dd51a99d6b08fead5ebc01b70cc213d57dc2 /compiler/GHC/CoreToStg/Prep.hs | |
| parent | 6844ead4f45620f0e9573762e9a892d1ae1609f4 (diff) | |
| download | haskell-e87b8e108303634af8a7247037d50ab10456c189.tar.gz | |
CPR: Detect constructed products in `runRW#` apps (#19822)
In #19822, we realised that the Simplifier's new habit of floating cases into
`runRW#` continuations inhibits CPR analysis from giving key functions of `text`
the CPR property, such as `singleton`.
This patch fixes that by anticipating part of !5667 (Nested CPR) to give
`runRW#` the proper CPR transformer it now deserves: Namely, `runRW# (\s -> e)`
should have the CPR property iff `e` has it.
The details are in `Note [Simplification of runRW#]` in GHC.CoreToStg.Prep.
The output of T18086 changed a bit: `panic` (which calls `runRW#`) now has
`botCpr`. As outlined in Note [Bottom CPR iff Dead-Ending Divergence], that's
OK.
Fixes #19822.
Metric Decrease:
T9872d
Diffstat (limited to 'compiler/GHC/CoreToStg/Prep.hs')
| -rw-r--r-- | compiler/GHC/CoreToStg/Prep.hs | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/compiler/GHC/CoreToStg/Prep.hs b/compiler/GHC/CoreToStg/Prep.hs index fa20e39e70..4fff314839 100644 --- a/compiler/GHC/CoreToStg/Prep.hs +++ b/compiler/GHC/CoreToStg/Prep.hs @@ -1310,6 +1310,14 @@ in straight-line code. Consequently, GHC.Core.Opt.SetLevels.lvlApp has special treatment for runRW# applications, ensure the arguments are not floated as MFEs. +Now that we float evaluation context into runRW#, we also have to give runRW# a +special higher-order CPR transformer lest we risk #19822. E.g., + + case runRW# (\s -> doThings) of x -> Data.Text.Text x something something' + ~> + runRW# (\s -> case doThings s of x -> Data.Text.Text x something something') + +The former had the CPR property, and so should the latter. Other considered designs ------------------------ |