Apparently gcc-6.2 with -O3 and -mfpu=neon can use ARM instructions
that requires 64bit alignment (here vst1.64) with data that
is not 64bit aligned (g->strcache) https://i.imgur.com/vYktsUn.png
So we need to be able to build "arm_neon_functions.cc" with
-mfpu=neon, while not automatically using NEON for the rest
of the codebase, unless explicitly asked for.
the proper check using compiler flags would be
defined(__ARM_NEON) || defined(__aarch64__)
however explicit wscript defined "ARM_NEON_SUPPORT" is prefereable.
This commit adds ARM NEON optimized routines for the following procedures
below:
*_compute_peak
*_find_peaks
*_apply_gain_to_buffer
*_mix_buffers_with_gain
*_mix_buffers_no_gain
*_copy_vector
NEON optimized routines have a prefix of: arm_neon_
Previously when the master-bus had more outputs than inputs,
Ardour crashed when the monitor-section was set up.
Removing a master-bus output port calls
Route::output_change_handler (master-bus)
-> Session::reset_monitor_section
which first removes the corresponding monitor-section input,
then output port. The latter triggers
ARDOUR::Route::output_change_handler (monitor-bus).
All with the process-lock held, so at this point in time Ardour
has removed the port-reference but the port still exists in the
backend.
Now the monitor-bus processors are re-configured and
the channel-count is updated. The port that was just removed
and triggered the ::output_change_handler() callback is
re-created.
unable to create port 'Monitor/audio_out 2': failed constructor
This fix changes the monitor-section to use strict-i/o (for plugins)
and also use master-bus output (not input) when configuring
processors.
Ardour's "pbd/i18n.h" needs to be included last,
after any include that may indirectly pull in getext or libintl.
For that reason "pbd/i18n.h" must not be used in header files either.
These are longer be used since Seuqnce has a "force_discrete"
boolen that needs to be taken into account in addition to
user-configurable ControlList _interpolation mode.
`_mm256_cvtss_f32` is only available in avxintrin.h of gcc-8 or
later. There it is defined as
```
extern __inline float
__attribute__ ((__gnu_inline__, __always_inline__, __artificial__))
_mm256_cvtss_f32 (__m256 __A)
{
return __A[0];
}
```
While explicit `vcurrent[0]` works with gcc-5 and gcc-6,
older gcc-4 fails with the following
error: invalid types 'float __vector__[int]' for array subscript
