On Thursday, 4 August 2016 at 21:13:23 UTC, Iain Buclaw wrote:
On 4 August 2016 at 01:00, Seb via Digitalmars-d
<digitalmars-d@puremagic.com> wrote:
To make matters worse std.math yields different results than
compiler/assembly intrinsics - note that in this example
import std.math.pow adds about 1K instructions to the output
assembler, whereas llvm_powf boils down to the assembly powf.
Of course the performance of powf is a lot better, I measured
[3] that e.g. std.math.pow takes ~1.5x as long for both LDC
and DMD. Of course if you need to run this very often, this
cost isn't acceptable.
This could be something specific to your architecture. I get
the same result on from all versions of powf, and from GCC
builtins too, regardless of optimization tunings.
I can reproduce this on DPaste (also x86_64).
https://dpaste.dzfl.pl/c0ab5131b49d
Behavior with a recent LDC build is similar (as annotated with
the comments).
