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Fix loop header duplicating code
- To: patches at x86-64 dot org, gcc-patches at gcc dot gnu dot org, rth at cygnus dot com
- Subject: Fix loop header duplicating code
- From: Jan Hubicka <jh at suse dot cz>
- Date: Fri, 27 Jul 2001 18:49:07 +0200
Hi,
it is amazing, that any loop with copied header gets ignored by loop optimizer
unless the header is eliminated by cse. The jump.c keeps jumps directly
to loop's label making loop.c to identify it as multiple entry one.
This patch should fix that. Hope that loop.c will get converted to cfg
in 3.1, but in case...
No more multiple entry loops in my testcases. Good.
Honza
Fri Jul 27 18:46:04 CEST 2001 Jan Hubicka <jh@suse.cz>
* jump.c (duplicate_loop_exit_test): Better test for jumps
entering the loop; create loop pre_header.
Index: jump.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/jump.c,v
retrieving revision 1.187
diff -c -3 -p -r1.187 jump.c
*** jump.c 2001/07/26 20:35:58 1.187
--- jump.c 2001/07/27 16:41:45
*************** duplicate_loop_exit_test (loop_start)
*** 304,309 ****
--- 304,310 ----
rtx lastexit;
int max_reg = max_reg_num ();
rtx *reg_map = 0;
+ rtx loop_pre_header_label;
/* Scan the exit code. We do not perform this optimization if any insn:
*************** duplicate_loop_exit_test (loop_start)
*** 404,409 ****
--- 405,411 ----
reg_map[REGNO (reg)] = gen_reg_rtx (GET_MODE (reg));
}
}
+ loop_pre_header_label = gen_label_rtx ();
/* Now copy each insn. */
for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
*************** duplicate_loop_exit_test (loop_start)
*** 474,482 ****
/* The jump_insn after loop_start should be followed
by barrier and loopback label. */
if (prev_nonnote_insn (label)
! && (PREV_INSN (prev_nonnote_insn (label))
! == NEXT_INSN (loop_start)))
! predict_insn_def (copy, PRED_LOOP_HEADER, TAKEN);
else
predict_insn_def (copy, PRED_LOOP_HEADER, NOT_TAKEN);
}
--- 476,489 ----
/* The jump_insn after loop_start should be followed
by barrier and loopback label. */
if (prev_nonnote_insn (label)
! && (prev_nonnote_insn (prev_nonnote_insn (label))
! == next_nonnote_insn (loop_start)))
! {
! predict_insn_def (copy, PRED_LOOP_HEADER, TAKEN);
! /* To keep pre-header, we need to redirect all loop
! entrances before the LOOP_BEG note. */
! redirect_jump (copy, loop_pre_header_label, 0);
! }
else
predict_insn_def (copy, PRED_LOOP_HEADER, NOT_TAKEN);
}
*************** duplicate_loop_exit_test (loop_start)
*** 510,515 ****
--- 517,524 ----
mark_jump_label (PATTERN (copy), copy, 0);
emit_barrier_before (loop_start);
}
+
+ emit_label_before (loop_pre_header_label, loop_start);
/* Now scan from the first insn we copied to the last insn we copied
(copy) for new pseudo registers. Do this after the code to jump to