[RFC] Kill gen_sequence

[David S. Miller]

   From: Geoff Keating <geoffk@geoffk.org>
   Date: 06 Jun 2002 12:13:46 -0700

   "David S. Miller" <davem@redhat.com> writes:
   
   > The idea of this patch is to eliminate usage of SEQUENCE rtl from
   > most of the compiler.  Usage remains in three areas:
   > 
   > 1) SSA.  It even hacks up the insns in the SEQUENCE array so
   >    that it's just the SETs.
   > 
   >    Maybe these bits can just be replaces with a parallel?
   
   Why would it be using a SEQUENCE if it meant PARALLEL?

Because SSA uses SEQUENCE rtl objects in it's very own internal way
that bears no relationship to how the rest of the compiler uses
SEQUENCE objects.

SSA is using the invariant that SEQUENCE rtl never exists in the
top level context insn list, so that when it sees SEQUENCE it knows
that it is one of these special SEQUENCE objects created specifically
for SSA.

The SSA sequence is not even an array of INSNs, it is an array of
PATTERNs of INSNs.  This representation is %100 internal to SSA.