Incorrect arch feature detection for Windows on ARM platforms

[shakan-qcom]

https://github.com/xiph/opus/blob/main/celt/arm/armcpu.c : opus_select_arch_impl() expects all feature bit to be set in sequential order : OPUS_ARCH_ARM_EDSP -> OPUS_ARCH_ARM_MEDIA -> OPUS_ARCH_ARM_NEON -> OPUS_ARCH_ARM_DOTPROD . and for Windows on ARM platforms, only NEON and DOTPROD (if supported) are set . This makes the function opus_select_arch_impl() to fail for first OPUS_ARCH_ARM_EDSP check and returns arch as ARM v4 , leading to hooking up C implementation of functions instead of NEON intrinsics.

[jmvalin]

Did you figure out what is causing the misdetection ? I don't have a Windows environment.

[shakan-qcom]

Oops , i am using opus from another SW stack and seems there is difference in detection logic in git vs the copy i have. I will verify and if no issues with this opensource version, let me close this issue.

[shakan-qcom]

I am using aarch64 Windows on ARM platform .

We can add support for checking DOT product support for Windows on ARM -

#ifndef PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE
#define PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE 43
#endif

if (IsProcessorFeaturePresent(PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE)) {
flags |= OPUS_CPU_ARM_DOTPROD_FLAG;
}

The instructions used for detecting other features are for aarch32 (NEON, MEDIA, EDSP etc) and am using aarch64 . would be good to remove all these instructions and set

flags |= OPUS_CPU_ARM_EDSP_FLAG | OPUS_CPU_ARM_MEDIA_FLAG | OPUS_CPU_ARM_NEON_FLAG;

default for all Windows on ARM (arch64) platforms and DOT product can be detected as mentioned above.
(I'm not sure if there exists an aarch32 Windows platform.)