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.

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 8497aa8603f26a79f4955b10719f0e52c30da141..106fa57addfd54f81c05dbb66660ecea636ecdaa 100644 (file)
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -13562,16 +13562,11 @@ 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