compiler/llvmGen/Llvm/Types.hs¶
Note [LLVM Float Types]¶
We use ‘ppDouble’ for both printing Float and Double floating point types. This is as LLVM expects all floating point constants (single & double) to be in IEEE 754 Double precision format. However, for single precision numbers (Float) they should be representable in IEEE 754 Single precision format. So the easiest way to do this is to narrow and widen again. (i.e., Double -> Float -> Double). We must be careful doing this that GHC doesn’t optimize that away.
Note [narrowFp & widenFp]¶
NOTE: we use float2Double & co directly as GHC likes to optimize away successive calls of ‘realToFrac’, defeating the narrowing. (Bug #7600). ‘realToFrac’ has inconsistent behaviour with optimisation as well that can also cause issues, these methods don’t.
