[commit: ghc] master: Make seq# evaluatedness look through casts (502026f)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/502026fc0a35460c7f04b26a11320723a7bbfdff/ghc

>---------------------------------------------------------------

commit 502026fc0a35460c7f04b26a11320723a7bbfdff
Author: David Feuer <david.feuer at gmail.com>
Date:   Mon Jun 11 10:32:23 2018 -0400

    Make seq# evaluatedness look through casts
    
    In d964b05, I forgot to look through casts to find the `seq#`
    identifier. Fix that.
    
    Reviewers: bgamari
    
    Reviewed By: bgamari
    
    Subscribers: rwbarton, thomie, carter
    
    Differential Revision: https://phabricator.haskell.org/D4804


>---------------------------------------------------------------

502026fc0a35460c7f04b26a11320723a7bbfdff
 compiler/coreSyn/CoreSyn.hs                               | 3 ++-
 testsuite/tests/perf/should_run/{T15226.hs => T15226a.hs} | 5 ++++-
 testsuite/tests/perf/should_run/all.T                     | 9 +++++++++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/compiler/coreSyn/CoreSyn.hs b/compiler/coreSyn/CoreSyn.hs
index 4dd70b0..50e40d1 100644
--- a/compiler/coreSyn/CoreSyn.hs
+++ b/compiler/coreSyn/CoreSyn.hs
@@ -2046,10 +2046,11 @@ collectArgs expr
     go e         as = (e, as)
 
 -- | Attempt to remove the last N arguments of a function call.
--- Strip off any ticks encountered along the way and any ticks
+-- Strip off any ticks or coercions encountered along the way and any
 -- at the end.
 stripNArgs :: Word -> Expr a -> Maybe (Expr a)
 stripNArgs !n (Tick _ e) = stripNArgs n e
+stripNArgs n (Cast f _) = stripNArgs n f
 stripNArgs 0 e = Just e
 stripNArgs n (App f _) = stripNArgs (n - 1) f
 stripNArgs _ _ = Nothing
diff --git a/testsuite/tests/perf/should_run/T15226.hs b/testsuite/tests/perf/should_run/T15226a.hs
similarity index 89%
copy from testsuite/tests/perf/should_run/T15226.hs
copy to testsuite/tests/perf/should_run/T15226a.hs
index 4c09114..6e9a1db 100644
--- a/testsuite/tests/perf/should_run/T15226.hs
+++ b/testsuite/tests/perf/should_run/T15226a.hs
@@ -3,6 +3,7 @@ import Control.Exception (evaluate)
 
 -- Just in case Prelude.repeat changes for some reason.
 import Prelude hiding (repeat)
+import Data.Coerce
 
 -- We want to be sure that the compiler *doesn't* know that
 -- all the elements of the list are in WHNF, because if it
@@ -12,11 +13,13 @@ repeat a = res
   where res = a : res
 {-# NOINLINE repeat #-}  -- Belt *and* suspenders
 
+newtype Foo = Foo Int
+
 silly :: [Int] -> IO ()
 silly = foldr go (pure ())
   where
     go x r = do
-      x' <- evaluate x
+      x' <- (coerce (evaluate :: Foo -> IO Foo) :: Int -> IO Int) x
       evaluate (x' + 3)  -- GHC should know that x' has been evaluated,
                          -- so this calculation will be erased entirely.
                          -- Otherwise, we'll create a thunk to pass to
diff --git a/testsuite/tests/perf/should_run/all.T b/testsuite/tests/perf/should_run/all.T
index b248dd5..0e7996ef 100644
--- a/testsuite/tests/perf/should_run/all.T
+++ b/testsuite/tests/perf/should_run/all.T
@@ -584,3 +584,12 @@ test('T15226',
      only_ways(['normal'])],
     compile_and_run,
     ['-O'])
+
+test('T15226a',
+    [stats_num_field('bytes allocated',
+                    [ (wordsize(64), 41040, 5) ]),
+                    # 2018-06-06   41040  Look through casts for seq#
+                    # initial  400041040
+     only_ways(['normal'])],
+    compile_and_run,
+    ['-O'])