Files
simdjson-simdjson/include/simdjson/ppc64/bitmask.h
T
strager 5510089d45 Improve build times for debug builds (#1859)
* Rename simdjson_really_inline -> simdjson_inline

I want to change the simdjson_really_inline macro to sometimes not force
inlining. After that upcoming change, the name simdjson_really_inline
will no longer makes sense.

Rename simdjson_really_inline to simdjson_inline. This patch should not
change semantics; simdjson_inline still forces inlining as before.

Some functions still need to be really inlined for ABI reasons.
(GCC's -Wpsabi complains otherwise.) Leave those functions marked as
simdjson_really_inline.

* Improve build times for debug builds

simdjson_inline is used for most simdjson functions. It forces inlining.
In unoptimized/debug builds, this can lead to a lot of machine code
being generated (especially with Address Sanitizer), causing slow
compilation.

Change simdjson_inline to force inlining only for optimized builds.

Sometimes, the programmer might want a slightly-optimized build and want
fast compilation (e.g. GCC's -Og mode). Allow simdjson users to define
the simdjson_inline macro themselves (e.g. on the command line:
-Dsimdjson_inline=inline) in cases where the default behavior is
undesired.

This patch reduced build times by over 75% for ondemand_object_tests.cpp
with GCC 9.4.0 and CMAKE_BUILD_TYPE=Debug on my AMD 5950X:

Before: 6.885 6.683 6.971 6.957 6.949 seconds (5 samples)
After:  1.492 1.551 1.494 1.490 1.531 seconds (5 samples)
2022-07-19 15:14:33 -04:00

43 lines
1.4 KiB
C++

#ifndef SIMDJSON_PPC64_BITMASK_H
#define SIMDJSON_PPC64_BITMASK_H
namespace simdjson {
namespace SIMDJSON_IMPLEMENTATION {
namespace {
//
// Perform a "cumulative bitwise xor," flipping bits each time a 1 is
// encountered.
//
// For example, prefix_xor(00100100) == 00011100
//
simdjson_inline uint64_t prefix_xor(uint64_t bitmask) {
// You can use the version below, however gcc sometimes miscompiles
// vec_pmsum_be, it happens somewhere around between 8 and 9th version.
// The performance boost was not noticeable, falling back to a usual
// implementation.
// __vector unsigned long long all_ones = {~0ull, ~0ull};
// __vector unsigned long long mask = {bitmask, 0};
// // Clang and GCC return different values for pmsum for ull so cast it to one.
// // Generally it is not specified by ALTIVEC ISA what is returned by
// // vec_pmsum_be.
// #if defined(__LITTLE_ENDIAN__)
// return (uint64_t)(((__vector unsigned long long)vec_pmsum_be(all_ones, mask))[0]);
// #else
// return (uint64_t)(((__vector unsigned long long)vec_pmsum_be(all_ones, mask))[1]);
// #endif
bitmask ^= bitmask << 1;
bitmask ^= bitmask << 2;
bitmask ^= bitmask << 4;
bitmask ^= bitmask << 8;
bitmask ^= bitmask << 16;
bitmask ^= bitmask << 32;
return bitmask;
}
} // unnamed namespace
} // namespace SIMDJSON_IMPLEMENTATION
} // namespace simdjson
#endif