Directly generating binary code [Was Re: Link-time optimzation]

[Andrew Haley <aph@redhat.com>]

Richard Earnshaw writes:

 > - Then, incrementally, we can bypass the parse layer to call routines
 > directly in the assembler.  This can be done both for directives and for
 > assembly of instructions.  *but it can all be done incrementally*.
 > 
 > The main difficulty is preserving -S output in a converted target if
 > that is requested.  It ought to be possible but it will need some care.

A nightmare scenario is debugging the compiler when its behaviour
changes due to using "-S".  Assembly source is something that we
maintainers use more than anyone else.

I expect that if we go down this road the gcc back end routines that
generate assembly source will rot.  I've seen compilers generate
"assembly" code that fails to assemble even though the binaries it
generated were correct.  Needless to say, this can make life very
difficult.

Andrew.