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| author | Sebastian Graf <sebastian.graf@kit.edu> | 2021-09-10 11:19:28 +0200 |
|---|---|---|
| committer | Sebastian Graf <sebastian.graf@kit.edu> | 2021-09-17 09:36:43 +0200 |
| commit | 92e0918c6f42223ede5524e3cb91f71728331a9a (patch) | |
| tree | f28cc283e76ce110f1afb30330ffc559c066e3f6 /compiler/GHC/Core/Rules.hs | |
| parent | 3fb1afea019422292954785575902c62473e93e3 (diff) | |
| download | haskell-wip/exec-freq.tar.gz | |
Statically estimate execution frequency of CoreAlts (#20378)wip/exec-freq
This patch implements #20378. See `Note [Estimating CoreAlt frequencies]` in the
new module GHC.Core.Opt.ExecFreq for details.
These were the changes:
1. Introduce `newtype Freq = Freq Float` as a type that captures relative
execution frequency and use it as an additional field in `CoreAlt`.
The default when we have no estimate available is `NoFreq`, e.g., NaN.
Otherwise, all `Freq`s of a `Case` should add up to 1.
Then fix up a whole bunch of use sites.
2. Introduce a new enum `Comparison` for the different kinds of comparison
operators (LessThan, GreaterOrEqual, NotEqual, ...). Then make `Compare`
primops also declare what kind of `Comparison` they do. Then introduce a
function `isComparisonApp_maybe` in GHC.Core.Utils that we can use for our
estimates (see below).
3. Write a static analysis pass `estimateAltFreqs`, that annotates `CoreAlt`s
with their relative execution `Freq`. These `Freq`s are determined by
combining the estimates of different branch heuristics, one of which uses
the new `isComparisonApp_maybe`.
The main function `estimateAltFreqs` is currently dead, but that is bound to
change in follow-up MRs.
Fixes #20378.
Diffstat (limited to 'compiler/GHC/Core/Rules.hs')
| -rw-r--r-- | compiler/GHC/Core/Rules.hs | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/compiler/GHC/Core/Rules.hs b/compiler/GHC/Core/Rules.hs index ff57df697f..014efc4c00 100644 --- a/compiler/GHC/Core/Rules.hs +++ b/compiler/GHC/Core/Rules.hs @@ -899,7 +899,7 @@ match_alts :: RuleMatchEnv -> Maybe RuleSubst match_alts _ subst [] [] = return subst -match_alts renv subst (Alt c1 vs1 r1:alts1) (Alt c2 vs2 r2:alts2) +match_alts renv subst (Alt c1 _f1 vs1 r1:alts1) (Alt c2 _f2 vs2 r2:alts2) | c1 == c2 = do { subst1 <- match renv' subst r1 r2 ; match_alts renv subst1 alts1 alts2 } @@ -1227,7 +1227,7 @@ ruleCheck env (Cast e _) = ruleCheck env e ruleCheck env (Let bd e) = ruleCheckBind env bd `unionBags` ruleCheck env e ruleCheck env (Lam _ e) = ruleCheck env e ruleCheck env (Case e _ _ as) = ruleCheck env e `unionBags` - unionManyBags [ruleCheck env r | Alt _ _ r <- as] + unionManyBags [ruleCheck env r | Alt _ _ _ r <- as] ruleCheckApp :: RuleCheckEnv -> Expr CoreBndr -> [Arg CoreBndr] -> Bag SDoc ruleCheckApp env (App f a) as = ruleCheck env a `unionBags` ruleCheckApp env f (a:as) |