LLVM/optimized code for sqrt incorrect for negative values
The LLVM sqrt intrinsic is undefined below values of -0.0
See http://llvm.org/docs/LangRef.html#llvm-sqrt-intrinsic
In some versions of LLVM it returns 0.0 in this case, but in newer versions the return value is undefined.
This causes the result of Haskell's sqrt to vary at negative values based on the codegen and optimization flags chosen.
main = print (sqrt (-7 :: Double))
$ ghc -O -fllvm Sqrt.hs
[1 of 1] Compiling Main ( Sqrt.hs, Sqrt.o )
Linking Sqrt ...
$ ./Sqrt
0.0
$ ghc -O Sqrt.hs
[1 of 1] Compiling Main ( Sqrt.hs, Sqrt.o )
Linking Sqrt ...
$ ./Sqrt
NaN
Trac metadata
Trac field | Value |
---|---|
Version | 7.8.4 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (LLVM) |
Test case | |
Differential revisions | |
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Blocking | |
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Operating system | |
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