We use a standard set of strict compiler warnings with Clang and GCC to
continuously test and maintain C89 conformance in the libjpeg API code.
However, SIMD extensions need not comply with that. The Neon code
specifically uses some C99isms, so disable
-Wdeclaration-after-statement, -Wc99-extensions, and -Wpedantic in the
scope of that code. Also modify the Neon feature tests so that they
will succeed if any of the aforementioned compiler warnings are enabled.
- Use the _M_ARM and _M_ARM64 macros provided by Visual Studio for
compile-time detection of Arm builds, since __arm__ and __aarch64__
are only present in GNU-compatible compilers.
- Neon/intrinsics: Use the _CountLeadingZeros() and
_CountLeadingZeros64() intrinsics provided by Visual Studio, since
__builtin_clz() and __builtin_clzl() are only present in
GNU-compatible compilers.
- Neon/intrinsics: Since Visual Studio does not support static vector
initialization, replace static initialization of Neon vectors with the
appropriate intrinsics. Compared to the static initialization
approach, this produces identical assembly code with both GCC and
Clang.
- Neon/intrinsics: Since Visual Studio does not support inline assembly
code, provide alternative code paths for Visual Studio whenever inline
assembly is used.
- Build: Set FLOATTEST appropriately for AArch64 Visual Studio builds
(Visual Studio does not emit fused multiply-add [FMA] instructions by
default for such builds.)
- Neon/intrinsics: Move temporary buffer allocation outside of nested
loops. Since Visual Studio configures Arm builds with a relatively
small amount of stack memory, attempting to allocate those buffers
within the inner loops caused a stack overflow.
Closes#461Closes#475
The previous AArch64 GAS implementation has been removed, since the
intrinsics implementation provides the same or better performance.
There was no previous AArch32 GAS implementation.
