Paolo Bonzini wrote:
Is there any particular function or pass that should be dealing with
IOR rx,0 - that I could trace thru and figure out why it does not
like it (or never gets there)?
I would be looking in combine and simplify-rtx (which is called by
combine). If your splitter triggers after combine, then I'm not
immediately sure where to look -- I'm not offhand aware of a pass
after combine which would call into simplify-rtx to perform this
optimization.
Me neither, but this
if (flag_expensive_optimizations)
{
/* Pass pc_rtx so no substitutions are done, just
simplifications. */
if (i1)
{
subst_low_luid = DF_INSN_LUID (i1);
i1src = subst (i1src, pc_rtx, pc_rtx, 0, 0);
}
else
{
subst_low_luid = DF_INSN_LUID (i2);
i2src = subst (i2src, pc_rtx, pc_rtx, 0, 0);
}
}
could be a place where it is done.
I'm still looking at this, but I don't see much of a chance to attack
this specific problem in the combiner.
I'm thinking this is going to need to be attacked along one of three
lines:
1. Having split_all_insns conditionally run a cleanup pass if
it's likely to be profitable (constant propagation &
rtl simplification)
2. Make local smarter about propagating constants and find
somewhere to simplify to eliminate the nops. Final could
do it much like it used to eliminate nop-moves and the like.
3. Investigate emitting better code in the splitters.
Jeff
