meson: Add support for building with precompiled headers

This substantially speeds up building for windows, due to the vast amount of
headers included via windows.h. A cross build from linux targetting mingw goes
from

994.11user 136.43system 0:31.58elapsed 3579%CPU
to
422.41user 89.05system 0:14.35elapsed 3562%CPU

The wins on windows are similar-ish (but I don't have a system at hand just
now for actual numbers). Targetting other operating systems the wins are far
smaller (tested linux, macOS, FreeBSD).

For now precompiled headers are disabled by default, it's not clear how well
they work on all platforms. E.g. on FreeBSD gcc doesn't seem to have working
support, but clang does.

When doing a full build precompiled headers are only beneficial for targets
with multiple .c files, as meson builds a separate precompiled header for each
target (so that different compilation options take effect). This commit
therefore only changes target with at least two .c files to use precompiled
headers.

Because this commit adds b_pch=false to the default_options new build
directories will have precompiled headers disabled by default, however
existing build directories will continue use the default value of b_pch, which
is true.

Note that using precompiled headers with ccache requires setting
CCACHE_SLOPPINESS=pch_defines,time_macros to get hits.

Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/CA+hUKG+50eOUbN++ocDc0Qnp9Pvmou23DSXu=ZA6fepOcftKqA@mail.gmail.com
Discussion: https://postgr.es/m/c5736f70-bb6d-8d25-e35c-e3d886e4e905@enterprisedb.com
Discussion: https://postgr.es/m/20190826054000.GE7005%40paquier.xyz

22 files changed, 34 insertions, 0 deletions

diff --git a/src/backend/meson.build b/src/backend/meson.build
index 6f4cd6ceb0..37562bae13 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -62,6 +62,7 @@ postgres_lib = static_library('postgres_lib',
   backend_sources + timezone_sources + generated_backend_sources,
   link_whole: backend_link_with,
   dependencies: backend_build_deps,
+  c_pch: pch_postgres_h,
   kwargs: internal_lib_args,
 )
 
@@ -81,6 +82,10 @@ if cc.get_id() == 'msvc'
 
   backend_link_args += '/DEF:@0@'.format(postgres_def.full_path())
   backend_link_depends += postgres_def
+  # Due to the way msvc and meson's precompiled headers implementation
+  # interact, we need to have symbols from the full library available. Could
+  # be restricted to b_pch=true.
+  backend_link_with += postgres_lib
 
 elif host_system == 'aix'
   # The '.' argument leads mkldexport.sh to emit "#! .", which refers to the
diff --git a/src/backend/snowball/meson.build b/src/backend/snowball/meson.build
index 974401d187..72959fa29d 100644
--- a/src/backend/snowball/meson.build
+++ b/src/backend/snowball/meson.build
@@ -66,6 +66,7 @@ endif
 
 dict_snowball = shared_module('dict_snowball',
   dict_snowball_sources,
+  c_pch: pch_postgres_h,
   kwargs: pg_mod_args + {
     'include_directories': [stemmer_inc],
   }
diff --git a/src/bin/pg_dump/meson.build b/src/bin/pg_dump/meson.build
index 3527a25c28..e66f632b54 100644
--- a/src/bin/pg_dump/meson.build
+++ b/src/bin/pg_dump/meson.build
@@ -13,6 +13,7 @@ pg_dump_common_sources = files(
 
 pg_dump_common = static_library('libpgdump_common',
   pg_dump_common_sources,
+  c_pch: pch_postgres_fe_h,
   dependencies: [frontend_code, libpq, zlib],
   kwargs: internal_lib_args,
 )
diff --git a/src/bin/pg_upgrade/meson.build b/src/bin/pg_upgrade/meson.build
index a7b927a45c..212bc9ce6e 100644
--- a/src/bin/pg_upgrade/meson.build
+++ b/src/bin/pg_upgrade/meson.build
@@ -24,6 +24,7 @@ endif
 
 pg_upgrade = executable('pg_upgrade',
   pg_upgrade_sources,
+  c_pch: pch_postgres_fe_h,
   dependencies: [frontend_code, libpq],
   kwargs: default_bin_args,
 )
diff --git a/src/bin/pgbench/meson.build b/src/bin/pgbench/meson.build
index 3cc393d17e..1a3ec5d129 100644
--- a/src/bin/pgbench/meson.build
+++ b/src/bin/pgbench/meson.build
@@ -27,6 +27,7 @@ pgbench = executable('pgbench',
   pgbench_sources,
   dependencies: [frontend_code, libpq, thread_dep],
   include_directories: include_directories('.'),
+  c_pch: pch_postgres_fe_h,
   c_args: host_system == 'windows' ? ['-DFD_SETSIZE=1024'] : [],
   kwargs: default_bin_args,
 )
diff --git a/src/bin/psql/meson.build b/src/bin/psql/meson.build
index 1264fc19fb..a4c46bf538 100644
--- a/src/bin/psql/meson.build
+++ b/src/bin/psql/meson.build
@@ -44,6 +44,7 @@ endif
 
 psql = executable('psql',
   psql_sources,
+  c_pch: pch_postgres_fe_h,
   include_directories: include_directories('.'),
   dependencies: [frontend_code, libpq, readline],
   kwargs: default_bin_args,
diff --git a/src/common/meson.build b/src/common/meson.build
index 23842e1ffe..1c9b8a3a01 100644
--- a/src/common/meson.build
+++ b/src/common/meson.build
@@ -147,6 +147,7 @@ foreach name, opts : pgcommon_variants
     endif
     c_args = opts.get('c_args', []) + common_cflags[cflagname]
     cflag_libs += static_library('libpgcommon@0@_@1@'.format(name, cflagname),
+      c_pch: pch_c_h,
       include_directories: include_directories('.'),
       kwargs: opts + {
         'sources': sources,
@@ -159,6 +160,7 @@ foreach name, opts : pgcommon_variants
 
   lib = static_library('libpgcommon@0@'.format(name),
       link_with: cflag_libs,
+      c_pch: pch_c_h,
       include_directories: include_directories('.'),
       kwargs: opts + {
         'dependencies': opts['dependencies'] + [ssl],
diff --git a/src/fe_utils/meson.build b/src/fe_utils/meson.build
index 3e226c260a..fe0b801387 100644
--- a/src/fe_utils/meson.build
+++ b/src/fe_utils/meson.build
@@ -23,6 +23,7 @@ fe_utils_sources += psqlscan
 
 fe_utils = static_library('libpgfeutils',
   fe_utils_sources + generated_headers,
+  c_pch: pch_postgres_fe_h,
   include_directories: [postgres_inc, libpq_inc],
   c_args: host_system == 'windows' ? ['-DFD_SETSIZE=1024'] : [],
   dependencies: frontend_common_code,
diff --git a/src/include/meson.build b/src/include/meson.build
index f2f7d03ff2..35c06c4856 100644
--- a/src/include/meson.build
+++ b/src/include/meson.build
@@ -114,6 +114,7 @@ install_headers(
 
 subdir('catalog')
 subdir('nodes')
+subdir('pch')
 subdir('storage')
 subdir('utils')
 
diff --git a/src/include/pch/c_pch.h b/src/include/pch/c_pch.h
new file mode 100644
index 0000000000..f40c757ca6
--- /dev/null
+++ b/src/include/pch/c_pch.h
@@ -0,0 +1 @@
+#include "c.h"
diff --git a/src/include/pch/meson.build b/src/include/pch/meson.build
new file mode 100644
index 0000000000..2bcec49c3a
--- /dev/null
+++ b/src/include/pch/meson.build
@@ -0,0 +1,4 @@
+# See https://github.com/mesonbuild/meson/issues/10338
+pch_c_h = meson.source_root() / meson.current_source_dir() / 'c_pch.h'
+pch_postgres_h = meson.source_root() / meson.current_source_dir() / 'postgres_pch.h'
+pch_postgres_fe_h = meson.source_root() / meson.current_source_dir() / 'postgres_fe_pch.h'
diff --git a/src/include/pch/postgres_fe_pch.h b/src/include/pch/postgres_fe_pch.h
new file mode 100644
index 0000000000..f3ea20912d
--- /dev/null
+++ b/src/include/pch/postgres_fe_pch.h
@@ -0,0 +1 @@
+#include "postgres_fe.h"
diff --git a/src/include/pch/postgres_pch.h b/src/include/pch/postgres_pch.h
new file mode 100644
index 0000000000..71b2f35f76
--- /dev/null
+++ b/src/include/pch/postgres_pch.h
@@ -0,0 +1 @@
+#include "postgres.h"
diff --git a/src/interfaces/ecpg/ecpglib/meson.build b/src/interfaces/ecpg/ecpglib/meson.build
index 7e6e6fbf5c..2d07da1ff4 100644
--- a/src/interfaces/ecpg/ecpglib/meson.build
+++ b/src/interfaces/ecpg/ecpglib/meson.build
@@ -27,6 +27,7 @@ ecpglib_st = static_library('libecpg',
   ecpglib_sources,
   include_directories: ecpglib_inc,
   c_args: ecpglib_c_args,
+  c_pch: pch_postgres_fe_h,
   dependencies: [frontend_stlib_code, thread_dep, libpq],
   link_with: [ecpg_pgtypes_st],
   kwargs: default_lib_args,
@@ -37,6 +38,7 @@ ecpglib_so = shared_library('libecpg',
   ecpglib_sources + ecpglib_so_sources,
   include_directories: ecpglib_inc,
   c_args: ecpglib_c_args,
+  c_pch: pch_postgres_fe_h,
   dependencies: [frontend_shlib_code, libpq, thread_dep],
   link_with: ecpg_pgtypes_so,
   soversion: host_system != 'windows' ? '6' : '',
diff --git a/src/interfaces/ecpg/pgtypeslib/meson.build b/src/interfaces/ecpg/pgtypeslib/meson.build
index 530dd2c602..d7e1a94d24 100644
--- a/src/interfaces/ecpg/pgtypeslib/meson.build
+++ b/src/interfaces/ecpg/pgtypeslib/meson.build
@@ -23,6 +23,7 @@ ecpg_pgtypes_st = static_library('libpgtypes',
   ecpg_pgtypes_sources,
   include_directories: ecpg_pgtypes_inc,
   c_args: ecpg_pgtypes_c_args,
+  c_pch: pch_postgres_fe_h,
   dependencies: frontend_stlib_code,
   kwargs: default_lib_args,
 )
@@ -32,6 +33,7 @@ ecpg_pgtypes_so = shared_library('libpgtypes',
   ecpg_pgtypes_sources + ecpg_pgtypes_so_sources,
   include_directories: ecpg_pgtypes_inc,
   c_args: ecpg_pgtypes_c_args,
+  c_pch: pch_postgres_fe_h,
   dependencies: frontend_shlib_code,
   version: '3.' + pg_version_major.to_string(),
   soversion: host_system != 'windows' ? '3' : '',
diff --git a/src/interfaces/ecpg/preproc/meson.build b/src/interfaces/ecpg/preproc/meson.build
index 74876f039c..3d42ee439f 100644
--- a/src/interfaces/ecpg/preproc/meson.build
+++ b/src/interfaces/ecpg/preproc/meson.build
@@ -102,6 +102,7 @@ endif
 ecpg_exe = executable('ecpg',
   ecpg_sources,
   include_directories: ['.', ecpg_inc, postgres_inc, libpq_inc],
+  c_pch: pch_postgres_fe_h,
   dependencies: [frontend_code],
   kwargs: default_bin_args,
 )
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 533b2e6f77..8e696f1183 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -58,6 +58,7 @@ libpq_st = static_library('libpq',
   libpq_sources,
   include_directories: [libpq_inc],
   c_args: libpq_c_args,
+  c_pch: pch_postgres_fe_h,
   dependencies: [frontend_stlib_code, libpq_deps],
   kwargs: default_lib_args,
 )
@@ -66,6 +67,7 @@ libpq_so = shared_library('libpq',
   libpq_sources + libpq_so_sources,
   include_directories: [libpq_inc, postgres_inc],
   c_args: libpq_c_args,
+  c_pch: pch_postgres_fe_h,
   version: '5.' + pg_version_major.to_string(),
   soversion: host_system != 'windows' ? '5' : '',
   darwin_versions: ['5', '5.' + pg_version_major.to_string()],
diff --git a/src/pl/plperl/meson.build b/src/pl/plperl/meson.build
index 535660085d..cd3894e6a7 100644
--- a/src/pl/plperl/meson.build
+++ b/src/pl/plperl/meson.build
@@ -45,6 +45,7 @@ endif
 
 plperl = shared_module('plperl',
   plperl_sources,
+  c_pch: pch_postgres_h,
   include_directories: [plperl_inc, postgres_inc],
   kwargs: pg_mod_args + {
     'dependencies': [perl_dep, pg_mod_args['dependencies']],
diff --git a/src/pl/plpgsql/src/meson.build b/src/pl/plpgsql/src/meson.build
index c46c0a1da2..27b2f5ef52 100644
--- a/src/pl/plpgsql/src/meson.build
+++ b/src/pl/plpgsql/src/meson.build
@@ -48,6 +48,7 @@ endif
 
 plpgsql = shared_module('plpgsql',
   plpgsql_sources,
+  c_pch: pch_postgres_h,
   include_directories: include_directories('.'),
   kwargs: pg_mod_args,
 )
diff --git a/src/pl/plpython/meson.build b/src/pl/plpython/meson.build
index 40888386b5..7bd683580e 100644
--- a/src/pl/plpython/meson.build
+++ b/src/pl/plpython/meson.build
@@ -36,6 +36,7 @@ endif
 
 plpython = shared_module('plpython3',
   plpython_sources,
+  c_pch: pch_postgres_h,
   include_directories: [plpython_inc, postgres_inc],
   kwargs: pg_mod_args + {
     'dependencies': [python3_dep, pg_mod_args['dependencies']],
diff --git a/src/pl/tcl/meson.build b/src/pl/tcl/meson.build
index f09bb14c95..7a708776c9 100644
--- a/src/pl/tcl/meson.build
+++ b/src/pl/tcl/meson.build
@@ -22,6 +22,7 @@ endif
 
 pltcl = shared_module('pltcl',
   pltcl_sources,
+  c_pch: pch_postgres_h,
   include_directories: [include_directories('.'), postgres_inc],
   kwargs: pg_mod_args + {
     'dependencies': [tcl_dep, pg_mod_args['dependencies']],
diff --git a/src/port/meson.build b/src/port/meson.build
index ced2e014db..c2222696f1 100644
--- a/src/port/meson.build
+++ b/src/port/meson.build
@@ -161,6 +161,7 @@ foreach name, opts : pgport_variants
     c_args = opts.get('c_args', []) + pgport_cflags[cflagname]
     cflag_libs += static_library('libpgport@0@_@1@'.format(name, cflagname),
       sources,
+      c_pch: pch_c_h,
       kwargs: opts + {
         'c_args': c_args,
         'build_by_default': false,
@@ -172,6 +173,7 @@ foreach name, opts : pgport_variants
   lib = static_library('libpgport@0@'.format(name),
       pgport_sources,
       link_with: cflag_libs,
+      c_pch: pch_c_h,
       kwargs: opts + {
         'dependencies': opts['dependencies'] + [ssl],
       }