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author | Ben Gamari <ben@smart-cactus.org> | 2019-06-04 00:42:10 -0400 |
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committer | Ben Gamari <ben@smart-cactus.org> | 2019-06-10 12:59:28 -0400 |
commit | 3b973df7b8909f250e02338ea27c881aaa37fa90 (patch) | |
tree | 64dad74011fd46516e3b04e82b386d1a28f87305 | |
parent | 799b1d26977b5841aa580e07c8f8e65356eed785 (diff) | |
download | haskell-3b973df7b8909f250e02338ea27c881aaa37fa90.tar.gz |
PrelRules: Ensure that string unpack/append rule fires with source noteswip/T16740
Previously the presence of source notes could hide nested applications
of `unpackFoldrCString#` from our constant folding logic. For instance,
consider the expression:
```haskell
unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n)
```
Specifically, ticks appearing in two places can defeat the rule:
a. Surrounding the inner application of `unpackFoldrCString#`
b. Surrounding the fold function, `c`
The latter caused the `str_rules` testcase to fail when `base` was built
with `-g3`.
Fixes #16740.
-rw-r--r-- | compiler/prelude/PrelRules.hs | 29 |
1 files changed, 18 insertions, 11 deletions
diff --git a/compiler/prelude/PrelRules.hs b/compiler/prelude/PrelRules.hs index bd18bfec63..943d8dc3b6 100644 --- a/compiler/prelude/PrelRules.hs +++ b/compiler/prelude/PrelRules.hs @@ -41,7 +41,7 @@ import TyCon ( tyConDataCons_maybe, isAlgTyCon, isEnumerationTyCon , isNewTyCon, unwrapNewTyCon_maybe, tyConDataCons , tyConFamilySize ) import DataCon ( dataConTagZ, dataConTyCon, dataConWorkId ) -import CoreUtils ( cheapEqExpr, exprIsHNF, exprType ) +import CoreUtils ( cheapEqExpr, cheapEqExpr', exprIsHNF, exprType, stripTicksTop, stripTicksTopT, mkTicks ) import CoreUnfold ( exprIsConApp_maybe ) import Type import OccName ( occNameFS ) @@ -1368,20 +1368,27 @@ match_append_lit _ id_unf _ [ Type ty1 , lit1 , c1 - , Var unpk `App` Type ty2 - `App` lit2 - `App` c2 - `App` n + , e2 ] - | unpk `hasKey` unpackCStringFoldrIdKey && - c1 `cheapEqExpr` c2 + -- N.B. Ensure that we strip off any ticks (e.g. source notes) from the + -- `lit` and `c` arguments, lest this may fail to fire when building with + -- -g3. See #16740. + | (strTicks, Var unpk `App` Type ty2 + `App` lit2 + `App` c2 + `App` n) <- stripTicksTop tickishFloatable e2 + , unpk `hasKey` unpackCStringFoldrIdKey + , cheapEqExpr' tickishFloatable c1 c2 + , (c1Ticks, c1') <- stripTicksTop tickishFloatable c1 + , c2Ticks <- stripTicksTopT tickishFloatable c2 , Just (LitString s1) <- exprIsLiteral_maybe id_unf lit1 , Just (LitString s2) <- exprIsLiteral_maybe id_unf lit2 = ASSERT( ty1 `eqType` ty2 ) - Just (Var unpk `App` Type ty1 - `App` Lit (LitString (s1 `BS.append` s2)) - `App` c1 - `App` n) + Just $ mkTicks strTicks + $ Var unpk `App` Type ty1 + `App` Lit (LitString (s1 `BS.append` s2)) + `App` mkTicks (c1Ticks ++ c2Ticks) c1' + `App` n match_append_lit _ _ _ _ = Nothing |