index on master: bf135f8 Merge pull request #502 from halide/split_rvar_bounds
On master: isnan
isnan
Disable const simplification
Fix Pull Request comments
Make fast inverse and fast inverse sqrt intrinsics instead.

They were coded for acceptable accuracy using a Newton step. This didn't get
the special values right (1/0 was not inf), and meant that they could
sometimes be slower than true division due to increased instruction latency!

I've removed the Newton step, and made them explicitly selected intrinsics
instead of something that triggers automatically.
Add gpu test and opencl implementation for fast inverse
Fix simd_op_check for new fast_inverse
Add newton update back to arm approx inverse

Otherwise it's way too inaccurate.
Another simd_op_check fix.
Merge branch 'isnan' of https://github.com/pgec/Halide into pgec-isnan
Merge pull request #519 from halide/fast_inverse

Fast inverse
Treat isnan more like an extern than an intrinsic

For uniformity with other similar math ops.

Also had to rename it to is_nan, because isnan is a macro on some platrforms.
Move is_nan_f64 to the double section for opencl
Merge branch 'pgec-isnan'
Merge branch 'master' of github.com:halide/Halide
Add Target::natural_vector_size<>()
Merge pull request #521 from halide/natural_vector_size

Add Target::natural_vector_size<>()
Add <limits> to Target.h