rtl-ssa: Extend make_uses_available

The first in-tree use of RTL-SSA was fwprop, and one of the goals
was to make the fwprop rewrite preserve the old behaviour as far
as possible.  The switch to RTL-SSA was supposed to be a pure
infrastructure change.  So RTL-SSA has various FIXMEs for things
that were artifically limited to faciliate the old-fwprop vs.
new-fwprop comparison.

One of the things that fwprop wants to do is extend live ranges, and
function_info::make_use_available tried to keep within the cases that
old fwprop could handle.

Since the information is built in extended basic blocks, it's easy
to handle intra-EBB queries directly.  This patch does that, and
removes the associated FIXME.

To get a flavour for how much difference this makes, I tried compiling
the testsuite at -Os for at least one target per supported CPU and OS.
For most targets, only a handful of tests changed, but the vast majority
of changes were positive.  The only target that seemed to benefit
significantly was i686-apple-darwin.

The main point of the patch is to remove the FIXME and to enable
the upcoming post-RA late-combine pass to handle more cases.

gcc/
	* rtl-ssa/functions.h (function_info::remains_available_at_insn):
	New member function.
	* rtl-ssa/accesses.cc (function_info::remains_available_at_insn):
	Likewise.
	(function_info::make_use_available): Avoid false negatives for
	queries within an EBB.

0 files changed, 0 insertions, 0 deletions