It is the default for width != 1 now.
Work on this never was finished, so it probably does not work anyway.

This is done by introducing a new new_global_entity() function for
constructing globals/adding a visibility argument to new_alias_entity().

This is handled earlier and there are no memory clobbers anymore in gen_ASM().

In particular remove the unnecessary 'sparc_is_valid_clobber()'.
The wrapper 'be_is_valid_clobber()' already handles 'memory' and 'cc'.

This flag can be set on entities where the actual address isn't
known/compared against other address. This also fixes a bug where we
used the mach-o csrings section for global char arrays which need
distinct addresses.

This resolves problems with hidden dependencies during code selection, which cause dependency cycles and therefore fixes backend/scheduled.c.
Also it grants the code selection slightly more freedom by not arbitrarily restricting the order by stack dependencies.

be: Pass the input requirements directly to the constructors of nodes, which have a variable number of arguments.

Properly use get_irn_pinned/set_irn_pinned as bool value instead of
comparing setting the ir_op enum values.

This adds two builtin kinds, ir_bk_va_start and ir_bk_va_arg. va_arg Builtins
are lowered in the lower_builtins pass with a function provided by the backend,
whereby most architectures can use be_default_lower_va_args. va_start Builtins
are lowered in the backend.

Note: This commit breaks all backends except for IA32. SPARC and AMD64 are
implemented in later commits. The ARM backend previously miscompiled variadic
functions, and will now throw a proper error.

All backends have similar empty Start nodes, which just provide registers.
So having one generic backend Start node to share some infrastructure is sensible.

Duplicate Projs are a problem when CSE is off, e.g. -O0.

It is like new_r_Proj(), but the mode is determined automatically from the out requirement of the predecessor.
This probably resolves some mode mismatches in untested code paths -- AMD64 backend and SPARC hard float, I'm looking at you!

Their values are either unused or trivial, i.e. result k has reg_offset k.

This is simpler, removes some code duplication and makes the backends more robust against duplicate Projs of Start, which can happen if optimisations are disabled.

- Rename other_different field to must_be_different
- Remove arch_register_req_type_must_be_different, it's enough to see
  if the must_be_different field is not zero.

- Rename other_same field to should_be_same.
- Remove arch_register_req_type_other_same, it's enough to see if the
  should_be_same field is not zero.

We can easily identify the outputs producing a stack pointer by looking
if the stack pointer register is assigned. Unfortunately this also
needed a new mechanism to tell the verifier that some registers are not
in SSA form (all the time) which needs a few extra lines in each
backend.

Get the obstack from the given start node.