This patch adds minimal support for dynamic ARM NEON support,
i.e. the ability to probe the CPU at runtime for NEON and
provide alternate code paths when it is available.
- Add include/core/SkUtilsArm.h, which declares a few helper
macros (e.g. SK_NEON_ARM_IS_DYNAMIC), plus the handy
function 'sk_cpu_arm_has_neon()' which returns true if
the target CPU supports the ARM NEON instruction set.
Note that the header is in include/core/ because it will
have to be included from NEON-specific code under src/code/
It would probably be more logical to put it under include/opts/
instead, but this would require moving all the NEON-specific
stuff under src/code/ into src/opts/, which is not trivial
due to the way the code is currently architected.
- Add src/core/SkUtilsArm.cpp which implements
'sk_cpu_arm_has_neon' for ARM-based Linux systems, only
when SK_NEON_ARM_IS_DYNAMIC is true.
(For other cases, 'sk_cpu_arm_has_neon' is an inline function
that returns a constant 'true' or 'false' value).
There is no user-level accessible CPUID instruction on ARM,
so do all CPU feature probing by parsing /proc/cpuinfo.
This is Linux-specific.
For Debug build types, the CPU probing result is printed
to the Android log (or Linux command-line) for easier
debugging.
- Create a new 'opts_neon' target (static library) which shall
contain all the NEON-specific code paths for the library.
This is necessary because -mfpu=neon impacts also non-scalar
code. Just like with -mssse3 on x86, we can't build the rest
of the library with this flag.
Note that for now, we only include memset16_neon and
memset32_neon in this library.
- Modify opts_check_arm.cpp to implement SK_ARM_NEON_IS_DYNAMIC
properly.
Compared to a 'xoom' build, the only difference is the use of
NEON-optimized memset16/32 functions. Later patches will move
more NEON-specific code paths to 'opts_neon'.
Review URL: https://codereview.appspot.com/6247058
git-svn-id: http://skia.googlecode.com/svn/trunk@4069 2bbb7eff-a529-9590-31e7-b0007b416f81
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