[Git][ghc/ghc][master] Bignum: fix bigNatCompareWord# bug (#18813)

[Marge Bot]

 Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
74ee1237 by Sylvain Henry at 2020-10-10T14:51:20-04:00
Bignum: fix bigNatCompareWord# bug (#18813)

- - - - -


4 changed files:

- libraries/ghc-bignum/src/GHC/Num/BigNat.hs
- + testsuite/tests/lib/integer/T18813.hs
- + testsuite/tests/lib/integer/T18813.stdout
- testsuite/tests/lib/integer/all.T


Changes:

=====================================
libraries/ghc-bignum/src/GHC/Num/BigNat.hs
=====================================
@@ -339,7 +339,7 @@ bigNatCompareWord# a b
    | bigNatIsZero a                   = cmpW# 0## b
    | isTrue# (wordArraySize# a ># 1#) = GT
    | True
-   = cmpW# (indexWordArray# a 1#) b
+   = cmpW# (indexWordArray# a 0#) b
 
 -- | Compare a BigNat and a Word
 bigNatCompareWord :: BigNat# -> Word -> Ordering


=====================================
testsuite/tests/lib/integer/T18813.hs
=====================================
@@ -0,0 +1,22 @@
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE MagicHash    #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# OPTIONS_GHC -O0 #-}
+
+import GHC.Exts
+import GHC.Num.BigNat  (bigNatCompareWord#, bigNatFromWord#)
+import GHC.Num.Integer (integerGcd)
+
+main :: IO ()
+main = do
+   let
+      x = noinline (14205695611797621937 :: Integer)
+      y = noinline (2 :: Word)
+   print (integerGcd x (toInteger y))
+   print (toInteger (gcd (fromInteger x) y :: Word))
+
+   let
+      x@(W# x#) = 1 :: Word
+      !x'       = bigNatFromWord# x#
+   print (bigNatCompareWord# x' x#)
+   print (compare x x)


=====================================
testsuite/tests/lib/integer/T18813.stdout
=====================================
@@ -0,0 +1,4 @@
+1
+1
+EQ
+EQ


=====================================
testsuite/tests/lib/integer/all.T
=====================================
@@ -11,6 +11,7 @@ test('integerPowMod', [], compile_and_run, [''])
 test('integerGcdExt', [], compile_and_run, [''])
 test('integerRecipMod', [], compile_and_run, [''])
 test('bignumMatch', [], compile, [''])
+test('T18813', [], compile_and_run, [''])
 
 # skip ghci as it doesn't support unboxed tuples
 test('integerImportExport', [omit_ways(['ghci'])], compile_and_run, [''])



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/74ee1237bf243dd7d8b758a53695575c364c3088

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/74ee1237bf243dd7d8b758a53695575c364c3088
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