docs: Fix up __sync_* documentation [PR117642]

The PR14311 commit which added support for __sync_* builtins documented that
there is a warning if a particular operation cannot be implemented.
But that commit nor anything later on implemented such warning, it was
always silent generation of the mentioned calls (which can in most cases
result in linker errors of course because those functions aren't implemented
anywhere, in libatomic or elsewhere in code shipped in gcc).

So, the following patch just adjust the documentation to match the
implementation.

2024-11-28  Jakub Jelinek  <jakub@redhat.com>

	PR target/117642
	* doc/extend.texi: Remove documentation of warning for unimplemented
	__sync_* operations, such warning has never been implemented.

(cherry picked from commit 0dcc09a8b5eb275ce939daad2bdfc7076ae1863c)

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 39fae6c8cd451cf45af5ae8a9e7c6022f8b9f4c9..b9ea00f10c625713ebc0b75e291065ee4d7befb4 100644 (file)
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -12216,16 +12216,11 @@ builtins (@pxref{__atomic Builtins}).  They should not be used for new
 code which should use the @samp{__atomic} builtins instead.
 
 Not all operations are supported by all target processors.  If a particular
-operation cannot be implemented on the target processor, a warning is
-generated and a call to an external function is generated.  The external
-function carries the same name as the built-in version,
-with an additional suffix
+operation cannot be implemented on the target processor, a call to an
+external function is generated.  The external function carries the same name
+as the built-in version, with an additional suffix
 @samp{_@var{n}} where @var{n} is the size of the data type.
 
-@c ??? Should we have a mechanism to suppress this warning?  This is almost
-@c useful for implementing the operation under the control of an external
-@c mutex.
-
 In most cases, these built-in functions are considered a @dfn{full barrier}.
 That is,
 no memory operand is moved across the operation, either forward or