Martin Storsjö authored Jun 06, 2019 and Janne Grunau committed Jun 07, 2019

This fixes building with raspbian compilers, that default to armv6.
The isb instruction is unavailable on armv6, and the cycle counter
register is accessed differently there as well.

This fixes issue #282.

nasm -v can actually fail for example on macOS, where nasm could be a
stub executable that forwards commands to the real nasm, but if the real
nasm is not installed, fails.
This would lead to a confusing error message due to the out of bounds
array access, to avoid that, explicitly check the exit code.

Needed for oss-fuzz after switching to '-fsanitize=fuzzer' for the
libfuzzer based build. Adding '-fsanitize=fuzzer' for all oss-fuzz based
build breaks afl.

This way adding new fields in the future will not require breaking ABI

The armv7 runner doesn't seem to cope well with the testdata though.

Also make sure that the w4 case can exit after processing 12 pixels,
where it is convenient.

This gives a small slowdown for in-order cores like A7, A8, A53, but
acutally seems to give a small speedup for out-of-order cores like
A9, A72 and A73.

AArch64:
Before:                      Cortex A53     A72     A73
mc_8tap_regular_w8_v_8bpc_neon:   223.8   247.3   228.5
After:
mc_8tap_regular_w8_v_8bpc_neon:   232.5   243.9   223.4

AArch32:
Before:                       Cortex A7      A8      A9     A53     A72     A73
mc_8tap_regular_w8_v_8bpc_neon:   550.2   470.7   520.5   257.0   256.4   248.2
After:
mc_8tap_regular_w8_v_8bpc_neon:   554.3   474.2   511.6   267.5   252.6   246.8

Henrik Gramner authored May 18, 2019 and Henrik Gramner committed May 18, 2019

The last 1/4 of the mask is always zero, so we can skip some
calculations that doesn't change the output.

Improves performance on 32-bit platforms over using uint64_t.

GCC                     Cortex A53   A72   A73
msac_decode_bool_c:           29.9  17.9  23.2
msac_decode_bool_neon:        27.4  15.3  20.4
msac_decode_bool_adapt_c:     49.2  26.8  31.0
msac_decode_bool_adapt_neon:  38.2  22.2  25.4
msac_decode_bool_equi_c:      26.6  16.8  19.4
msac_decode_bool_equi_neon:   23.9  13.7  15.7

Clang                   Cortex A53   A72   A73
msac_decode_bool_c:           28.0  16.4  23.1
msac_decode_bool_neon:        26.9  14.6  21.0
msac_decode_bool_adapt_c:     46.8  25.1  31.4
msac_decode_bool_adapt_neon:  36.2  19.0  26.2
msac_decode_bool_equi_c:      23.7  13.4  18.8
msac_decode_bool_equi_neon:   23.7  11.3  14.2

This is as fast as, or faster than, what either GCC or Clang
produces.

Justin Bull authored May 14, 2019 and Jean-Baptiste Kempf committed May 14, 2019

Closes #274

Henrik Gramner authored May 10, 2019 and Henrik Gramner committed May 14, 2019

Prevents overflows in malloc size calculations.

The spec states that a decoder should instead ignore them. Otherwise, streams
compliant with an hypothetical future revision of the spec may be rejected when
backwards compatibility is expected.