On Fri, 2007-08-17 at 09:32 -0400, Kenneth Zadeck wrote:
> The problem comes where you have a store that uses 2 or more hard regs
> but one or more of those hardregs is unused.
>
> In a forwards scan, ALL of the set regs will interfere with anything
> live until the last set reg goes dead. In a backwards scan, the unused
> hard regs never cause interferences.
> global/reload wants these interferences.
Can you cut/paste the problematic RTL here? I'm having a hard time
seeing what your problem is since "store"'s (excluding store with update
insns) don't have any set regs, so we shouldn't get any inferences for
store insns.
> 2) We could turn off local. I was planning on testing this anyway
> because i want to see if local, at this point, is just making global do
> a bad job. However, my hope is that global or the new allocator from
> vlad is smart enough to properly handle the case where some parts of a
> multiword set are dead.
Offline, I gave Kenny a patch to disable local_alloc. I'm appending it
here for posterity.
Peter
Index: opts.c
===================================================================
--- opts.c (revision 127398)
+++ opts.c (working copy)
@@ -895,6 +895,8 @@ decode_options (unsigned int argc, const
set_param_value ("min-crossjump-insns", 1);
}
+ flag_local_alloc = 1;
+
/* Initialize whether `char' is signed. */
flag_signed_char = DEFAULT_SIGNED_CHAR;
/* Set this to a special "uninitialized" value. The actual default
is set
Index: local-alloc.c
===================================================================
--- local-alloc.c (revision 127398)
+++ local-alloc.c (working copy)
@@ -363,6 +363,9 @@ local_alloc (void)
registers. */
update_equiv_regs ();
+ if (! flag_local_alloc)
+ return recorded_label_ref;
+
/* This sets the maximum number of quantities we can have. Quantity
numbers start at zero and we can have one for each pseudo. */
max_qty = (max_regno - FIRST_PSEUDO_REGISTER);
Index: common.opt
===================================================================
--- common.opt (revision 127398)
+++ common.opt (working copy)
@@ -628,6 +628,10 @@ fleading-underscore
Common Report Var(flag_leading_underscore) Init(-1)
Give external symbols a leading underscore
+flocal-alloc
+Common Report Var(flag_local_alloc)
+Perform local register allocation
+
floop-optimize
Common
Does nothing. Preserved for backward compatibility.
