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Require compiler barrier support.

Previously we had a fallback implementation of pg_compiler_barrier()that called an empty function across a translation unit boundary so thecompiler couldn't see what it did. That shouldn't be needed on anycurrent systems, and might not even work with a link time optimizer.Since we now require compiler-specific knowledge of how to implementatomics, we should also know how to implement compiler barriers on ahypothetical new system.Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>Suggested-by: Andres Freund <andres@anarazel.de>Discussion:https://postgr.es/m/721bf39a-ed8a-44b0-8b8e-be3bd81db748%40technowledgy.deDiscussion:https://postgr.es/m/3351991.1697728588%40sss.pgh.pa.us

1 parent8138526 commita011dc3Copy full SHA for a011dc3

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3 files changed

-23

lines changed

src
- backend/port
  - atomics.c
- include/port
  - atomics.h
  - atomics
    - fallback.h

3 files changed

-23

lines changed

`‎src/backend/port/atomics.c‎`

Lines changed: 0 additions & 8 deletions

Original file line number	Diff line number	Diff line change
`@@ -40,14 +40,6 @@ pg_spinlock_barrier(void)`
`40`	`40`	`}`
`41`	`41`	`#endif`
`42`	`42`
`43`		`-#ifdefPG_HAVE_COMPILER_BARRIER_EMULATION`
`44`		`-void`
`45`		`-pg_extern_compiler_barrier(void)`
`46`		`-{`
`47`		`-/* do nothing */`
`48`		`-}`
`49`		`-#endif`
`50`		`-`
`51`	`43`
`52`	`44`	`#ifdefPG_HAVE_ATOMIC_U64_SIMULATION`
`53`	`45`

`‎src/include/port/atomics.h‎`

Lines changed: 3 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -98,6 +98,9 @@`
`98`	`98`	`#if !defined(PG_HAVE_ATOMIC_U32_SUPPORT)`
`99`	`99`	`#error "could not find an implementation of pg_atomic_uint32"`
`100`	`100`	`#endif`
	`101`	`+#if !defined(pg_compiler_barrier_impl)`
	`102`	`+#error "could not find an implementation of pg_compiler_barrier"`
	`103`	`+#endif`
`101`	`104`
`102`	`105`	`/*`
`103`	`106`	`* Provide a spinlock-based implementation of the 64 bit variants, if`

`‎src/include/port/atomics/fallback.h‎`

Lines changed: 0 additions & 15 deletions

Original file line number	Diff line number	Diff line change
`@@ -33,21 +33,6 @@ extern void pg_spinlock_barrier(void);`
`33`	`33`	`#definepg_memory_barrier_impl pg_spinlock_barrier`
`34`	`34`	`#endif`
`35`	`35`
`36`		`-#ifndefpg_compiler_barrier_impl`
`37`		`-/*`
`38`		`- * If the compiler/arch combination does not provide compiler barriers,`
`39`		`- * provide a fallback. The fallback simply consists of a function call into`
`40`		`- * an externally defined function. That should guarantee compiler barrier`
`41`		`- * semantics except for compilers that do inter translation unit/global`
`42`		`- * optimization - those better provide an actual compiler barrier.`
`43`		`- *`
`44`		`- * A native compiler barrier for sure is a lot faster than this...`
`45`		`- */`
`46`		`-#definePG_HAVE_COMPILER_BARRIER_EMULATION`
`47`		`-externvoidpg_extern_compiler_barrier(void);`
`48`		`-#definepg_compiler_barrier_impl pg_extern_compiler_barrier`
`49`		`-#endif`
`50`		`-`
`51`	`36`
`52`	`37`	`#if !defined(PG_HAVE_ATOMIC_U64_SUPPORT)`
`53`	`38`

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Commita011dc3

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3 files changed

3 files changed

`‎src/backend/port/atomics.c‎`

`‎src/include/port/atomics.h‎`

`‎src/include/port/atomics/fallback.h‎`

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