Index: extend.texi
===================================================================
--- extend.texi	(revision 234245)
+++ extend.texi	(working copy)
@@ -7441,7 +7441,8 @@
 @end table
 
 @subsubheading Remarks
-Using extended @code{asm} typically produces smaller, safer, and more
+Using extended @code{asm} (@pxref{Extended Asm}) typically produces smaller,
+safer, and more
 efficient code, and in most cases it is a better solution than basic
 @code{asm}.  However, there are two situations where only basic @code{asm}
 can be used:
@@ -7481,10 +7482,25 @@
 symbol errors during compilation if your assembly code defines symbols or 
 labels.
 
-Since GCC does not parse the @var{AssemblerInstructions}, it has no 
-visibility of any symbols it references. This may result in GCC discarding 
-those symbols as unreferenced.
+@strong{Warning:} The C standards do not specify semantics for @code{asm},
+making it a potential source of incompatibilities between compilers.  These
+incompatibilities may not produce compiler warnings/errors.
 
+GCC does not parse basic @code{asm}'s @var{AssemblerInstructions}, which
+means there is no way to communicate to the compiler what is happening
+inside them.  GCC has no visibility of symbols in the @code{asm} and may
+discard them as unreferenced.  It also does not know about side effects of
+the assembler code, such as modifications to memory or registers.  Unlike
+some compilers, GCC assumes that no changes to either memory or registers
+occur.  This assumption may change in a future release.
+
+To avoid complications from future changes to the semantics and the
+compatibility issues between compilers, consider replacing basic @code{asm}
+with extended @code{asm}.  See
+@uref{https://gcc.gnu.org/wiki/ConvertBasicAsmToExtended, How to convert
+from basic asm to extended asm} for information about how to perform this
+conversion.
+
 The compiler copies the assembler instructions in a basic @code{asm} 
 verbatim to the assembly language output file, without 
 processing dialects or any of the @samp{%} operators that are available with