The GNU builtin function __builtin_clzl() accepts an unsigned long
argument, which is 8 bytes wide on LP64 systems (most Un*x systems,
including Mac) but 4 bytes wide on LLP64 systems (Windows.) This caused
the Neon intrinsics implementation of Huffman encoding to produce
mathematically incorrect results when compiled using Visual Studio with
Clang.
This commit changes all invocations of __builtin_clzl() in the Neon SIMD
extensions to __builtin_clzll(), which accepts an unsigned long long
argument that is guaranteed to be 8 bytes wide on all systems.
Fixes#480Closes#490
- 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.
