#1916: compiling truncate :: Float -> Int with -O2 panics ghc
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Reporter: conal | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.8.1
Severity: normal | Resolution:
Keywords: | Difficulty: Easy (1 hr)
Testcase: | Architecture: Unknown
Os: Unknown |
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Changes (by int-e):
* difficulty: => Easy (1 hr)
Comment:
The code contains an expression of the form {{{(comparison (conversion
expr) int-literal)}}}. In {{{cmmMachOpFold}}}, the CMM optimizer tries to
narrow the literal down to the type of expr, to see if it fits and the
conversion can be eliminated. However this narrowing fails if {{{expr}}}
has a floating point type. And that's good, because the optimization is
not valid in that case.
The patch changes {{{cmmMachOpFold}}} to not even attempt narrowing to
floating point types.
It fixes the example above.
Affected architectures are x86 and x86_64 as it seems.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1916#comment:1>
GHC <http://www.haskell.org/ghc/>
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