Patch: Fix match_dup handling in web.c

[Bernd Schmidt]

I found a number of bugs while testing an ARM patch that rewrites the
ldm/stm peepholes.

In web.c, there is code that tries to detect match_dups by comparing
operands for equality; this is neither a necessary nor a sufficient
condition.  In particular, web.c cannot detect an input operand that
match_dups an in-out output operand; this can result in web.c breaking
match_dups and replacing only the inputs of an insn.

Fixed by the patch below.  Bootstrapped and regression tested on
i686-linux, together with some other fixes.  Ok?


Bernd
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