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| author | Matthew Craven <5086-clyring@users.noreply.gitlab.haskell.org> | 2022-04-27 15:38:20 -0400 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2022-05-05 12:48:47 -0400 |
| commit | 016f9ca683fc915d661b2c24321d3005a8929a47 (patch) | |
| tree | a697f332139a6104d60d89f8f98d8c0f2e5f3161 | |
| parent | 610d028348ca0aa2721d515961f14cb72416c17c (diff) | |
| download | haskell-016f9ca683fc915d661b2c24321d3005a8929a47.tar.gz | |
Fix broken rules for (^) with known small powers
| -rw-r--r-- | libraries/base/GHC/Real.hs | 23 | ||||
| -rw-r--r-- | testsuite/tests/lib/base/all.T | 2 |
2 files changed, 12 insertions, 13 deletions
diff --git a/libraries/base/GHC/Real.hs b/libraries/base/GHC/Real.hs index e6943b0d86..666034bdac 100644 --- a/libraries/base/GHC/Real.hs +++ b/libraries/base/GHC/Real.hs @@ -717,22 +717,21 @@ floated out before the rule has a chance to fire. Also desirable would be rules for (^^), but I haven't managed to get those to fire. -Note: Trying to save multiplications by sharing the square for -exponents 4 and 5 does not save time, indeed, for Double, it is -up to twice slower, so the rules contain flat sequences of -multiplications. +Note: Since (*) is not associative for some types (e.g. Double), it is +important that the RHS of these rules produce the same bracketing as +would the actual implementation of (^). A mismatch here led to #19569. -} -- See Note [Powers with small exponent] {-# RULES -"^2/Int" forall x. x ^ (2 :: Int) = let u = x in u*u -"^3/Int" forall x. x ^ (3 :: Int) = let u = x in u*u*u -"^4/Int" forall x. x ^ (4 :: Int) = let u = x in u*u*u*u -"^5/Int" forall x. x ^ (5 :: Int) = let u = x in u*u*u*u*u -"^2/Integer" forall x. x ^ (2 :: Integer) = let u = x in u*u -"^3/Integer" forall x. x ^ (3 :: Integer) = let u = x in u*u*u -"^4/Integer" forall x. x ^ (4 :: Integer) = let u = x in u*u*u*u -"^5/Integer" forall x. x ^ (5 :: Integer) = let u = x in u*u*u*u*u +"^2/Int" forall x. x ^ (2 :: Int) = x*x +"^3/Int" forall x. x ^ (3 :: Int) = x*x*x +"^4/Int" forall x. x ^ (4 :: Int) = let u = x*x in u*u +"^5/Int" forall x. x ^ (5 :: Int) = let u = x*x in u*u*x +"^2/Integer" forall x. x ^ (2 :: Integer) = x*x +"^3/Integer" forall x. x ^ (3 :: Integer) = x*x*x +"^4/Integer" forall x. x ^ (4 :: Integer) = let u = x*x in u*u +"^5/Integer" forall x. x ^ (5 :: Integer) = let u = x*x in u*u*x #-} ------------------------------------------------------- diff --git a/testsuite/tests/lib/base/all.T b/testsuite/tests/lib/base/all.T index b45171c8e2..8d88097a17 100644 --- a/testsuite/tests/lib/base/all.T +++ b/testsuite/tests/lib/base/all.T @@ -6,4 +6,4 @@ test('T17310', normal, compile, ['']) test('T19691', normal, compile, ['']) test('executablePath', extra_run_opts(config.os), compile_and_run, ['']) test('T17472', normal, compile_and_run, ['']) -test('T19569', expect_broken(19569), compile_and_run, ['']) +test('T19569', normal, compile_and_run, ['']) |