Unregisterised compiler: arithmetic failure

Compiling the following with RC2 on powerpc 64 downloaded from haskell.org:

main = putStr $ show (-1.0000000001 :: Double)

Setting -O yields:

0.0

Without optimization the correct result is displayed.

I prepared an unregisterised compiler on amd64 and see the same issue and more arithmetic tests fail in testsuite. In fact I took the above from arith005.

Trac metadata

Trac field	Value
Version	7.8.1-rc2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown/Multiple
Architecture

mentioned in issue #8819 (closed)

changed weight to 5

added Tbug Trac import labels

I should add I ran the tests on Linux.

Trac metadata

Trac field	Value
Operating system	Unknown/Multiple → Linux

Attached file mini-noopt.hc (download).

output of ghc -C

Attached file mini.hc (download).

output of ghc -O -C

I produced the attached files on my amd64 machine.

In line 26 of mini.hc (with -O optimization) we see a constant 0.0 whereas line 32 in mini-noopt.hc there is 1.0000000001 and a call to GHC.Num.negate.

changed milestone to %7.8.3

As this is a regression from 7.6.3 we should look into this for 7.8.3.

Trac metadata

Trac field	Value
Blocking	→ #8819 (closed)

changed milestone to %7.8.4

Moving to 7.8.4.

The following commit fixes the bug: https://phabricator.haskell.org/rGHC43f1b2ecd1960fa7377cf55a2b97c66059a701ef

added 1 deleted label

changed weight to 7

This ticket blocks #8819 (closed) which is priority high.

The commit mentioned in ticket:8849#comment:87799 applied cleanly when I prepared a patch file for the released 7.8.3 tarball. You should be able to just cherry-pick it. If not, please assign the ticket to me and let me know what you prefer: phabricator, patch file?

Trac metadata

Trac field	Value
Priority	normal → high

closed

These have been merged into ghc-7.8.

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

removed 1 deleted label

added incorrect runtime result label

added Phigh label