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+@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
+@c 1999, 2000, 2001, 2002, 2004 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Portability
+@chapter GCC and Portability
+@cindex portability
+@cindex GCC and portability
+
+GCC itself aims to be portable to any machine where @code{int} is at least
+a 32-bit type.  It aims to target machines with a flat (non-segmented) byte
+addressed data address space (the code address space can be separate).
+Target ABIs may have 8, 16, 32 or 64-bit @code{int} type.  @code{char}
+can be wider than 8 bits.
+
+GCC gets most of the information about the target machine from a machine
+description which gives an algebraic formula for each of the machine's
+instructions.  This is a very clean way to describe the target.  But when
+the compiler needs information that is difficult to express in this
+fashion, ad-hoc parameters have been defined for machine descriptions.
+The purpose of portability is to reduce the total work needed on the
+compiler; it was not of interest for its own sake.
+
+@cindex endianness
+@cindex autoincrement addressing, availability
+@findex abort
+GCC does not contain machine dependent code, but it does contain code
+that depends on machine parameters such as endianness (whether the most
+significant byte has the highest or lowest address of the bytes in a word)
+and the availability of autoincrement addressing.  In the RTL-generation
+pass, it is often necessary to have multiple strategies for generating code
+for a particular kind of syntax tree, strategies that are usable for different
+combinations of parameters.  Often, not all possible cases have been
+addressed, but only the common ones or only the ones that have been
+encountered.  As a result, a new target may require additional
+strategies.  You will know
+if this happens because the compiler will call @code{abort}.  Fortunately,
+the new strategies can be added in a machine-independent fashion, and will
+affect only the target machines that need them.