Clean up inconsistencies in CPU-identification macros.
In various places we depend on compiler-defined macros like __x86_64__
to guard CPU-type-specific code. However, those macros aren't very
well standardized; in particular, it emerges that MSVC doesn't define
any of the ones gcc does, but has its own. We were not coping with
that consistently, with the result that we're missing some useful
CPU-dependent optimizations in MSVC builds. There are also some
places that are checking randomly-different spellings that may
have been the only ones recognized by some old compilers, but we
weren't doing that consistently either.
Let's standardize on using gcc's long-form spellings (with trailing
underscores), after putting a stanza into c.h that ensures that these
spellings are defined even when the compiler provides some other one.
I put an "#else #error" branch into the c.h addition so that we'll
get an error if the compiler provides none of the symbols we're
expecting. That might be best removed in the end, since it might
annoy people trying to port to some new CPU type. But for testing
this it seems like a good idea, in case we've missed some common
variant spelling.
In addition to enabling some optimizations we previously missed on
MSVC, this cleans up a thinko. Several places used "_M_X64" in the
apparent belief that that's MSVC's equivalent to __x86_64__, but
it's not: it will also get defined on some but not all ARM64 builds.
Also, guard the x86_feature_available() stuff in pg_cpu.[hc] with
#if defined(__x86_64__) || defined(__i386__)
which seems like a more natural way of specifying what it applies to.
This builds on some previous work by Thomas Munro, but it requires
much less code churn because it re-uses gcc's names for the CPU-type
macros instead of inventing our own.
Author: Tom Lane <[email protected]>
Discussion:
https://postgr.es/m/CA+hUKGL8Hs-phHPugrWM=5dakct897rxyazyzlw-szxnzgx...@mail.gmail.com
Discussion: https://postgr.es/m/[email protected]
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/2ef57e636fc97528a37515673f5f56a1fcf97186
Modified Files
--------------
src/common/d2s.c | 2 +-
src/include/c.h | 58 +++++++++++++++++++++++++++++++++++-
src/include/port/atomics.h | 6 ++--
src/include/port/atomics/arch-x86.h | 4 +--
src/include/port/pg_bitutils.h | 4 +--
src/include/port/pg_cpu.h | 4 +--
src/include/portability/instr_time.h | 2 +-
src/include/storage/s_lock.h | 10 +++----
src/port/pg_cpu_x86.c | 6 ++--
9 files changed, 76 insertions(+), 20 deletions(-)
