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[PATCH] More aggressive jump bypassing
- From: Roger Sayle <roger at www dot eyesopen dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 16 Jan 2003 13:33:44 -0700 (MST)
- Subject: [PATCH] More aggressive jump bypassing
This is a repost of my "More aggressive jump bypassing" patch from
last June, http://gcc.gnu.org/ml/gcc-patches/2002-06/msg01392.html
The recent patch to split GCSE means that the bad interactions with
GCC's loop optimization passes are no longer a problem.
The current jump bypassing pass uses redirect_edge_and_branch
which works if the edge being directed is an unconditional
branch or the taken branch of a conditional jump. The patch
below replaces this with a call to redirect_edge_and_branch_force
which can additionally redirect branch not-taken edges, and
unconditional fall-thru edges.
Timings for this patch can be found as "Aggr" in the posting
http://gcc.gnu.org/ml/gcc/2002-09/msg01129.html [but from
Andreas SPEC runs last night, the relative improvements may
have varied somewhat since September].
The patch below has been tested on i686-pc-linux-gnu with a
full "make bootstrap", all languages except Ada and treelang,
and a complete "make -k check" with no new regressions.
Ok for mainline?
2003-01-16 Roger Sayle <roger@eyesopen.com>
* gcse.c (bypass_last_basic_block): New global variable.
(bypass_block): Use redirect_edge_and_branch_force to redirect
fall-through edges. Use bypass_last_basic_block to determine
which blocks have valid PRE information.
(bypass_conditional_jumps): Initialize bypass_last_basic_block.
Index: gcse.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/gcse.c,v
retrieving revision 1.226
diff -c -3 -p -r1.226 gcse.c
*** gcse.c 16 Jan 2003 01:06:32 -0000 1.226
--- gcse.c 16 Jan 2003 15:22:25 -0000
*************** one_cprop_pass (pass, cprop_jumps, bypas
*** 4509,4514 ****
--- 4509,4521 ----
/* Bypass conditional jumps. */
+ /* The value of last_basic_block at the beginning of the jump_bypass
+ pass. The use of redirect_edge_and_branch_force may introduce new
+ basic blocks, but the data flow analysis is only valid for basic
+ block indices less than bypass_last_basic_block. */
+
+ static int bypass_last_basic_block;
+
/* Find a set of REGNO to a constant that is available at the end of basic
block BB. Returns NULL if no such set is found. Based heavily upon
find_avail_set. */
*************** bypass_block (bb, setcc, jump)
*** 4579,4584 ****
--- 4586,4598 ----
for (e = bb->pred; e; e = enext)
{
enext = e->pred_next;
+ if (e->flags & EDGE_COMPLEX)
+ continue;
+
+ /* We can't redirect edges from new basic blocks. */
+ if (e->src->index >= bypass_last_basic_block)
+ continue;
+
for (i = 0; i < reg_use_count; i++)
{
struct reg_use *reg_used = ®_use_table[i];
*************** bypass_block (bb, setcc, jump)
*** 4612,4623 ****
else
dest = NULL;
- /* Once basic block indices are stable, we should be able
- to use redirect_edge_and_branch_force instead. */
old_dest = e->dest;
! if (dest != NULL && dest != old_dest
! && redirect_edge_and_branch (e, dest))
! {
/* Copy the register setter to the redirected edge.
Don't copy CC0 setters, as CC0 is dead after jump. */
if (setcc)
--- 4626,4638 ----
else
dest = NULL;
old_dest = e->dest;
! if (dest != NULL
! && dest != old_dest
! && dest != EXIT_BLOCK_PTR)
! {
! redirect_edge_and_branch_force (e, dest);
!
/* Copy the register setter to the redirected edge.
Don't copy CC0 setters, as CC0 is dead after jump. */
if (setcc)
*************** bypass_conditional_jumps ()
*** 4660,4665 ****
--- 4675,4682 ----
/* Note we start at block 1. */
if (ENTRY_BLOCK_PTR->next_bb == EXIT_BLOCK_PTR)
return 0;
+
+ bypass_last_basic_block = last_basic_block;
changed = 0;
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb->next_bb,
Roger
--
Roger Sayle, E-mail: roger@eyesopen.com
OpenEye Scientific Software, WWW: http://www.eyesopen.com/
Suite 1107, 3600 Cerrillos Road, Tel: (+1) 505-473-7385
Santa Fe, New Mexico, 87507. Fax: (+1) 505-473-0833