diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b550aa24cd55948ae09d19094417dc81c0e19934..5829711c123dedd082061e50b471f0f3c26ece0d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2007-09-20 Richard Sandiford <rsandifo@nildram.co.uk>
+
+ * dse.c (find_shift_sequence): No-op rework of control flow.
+
2007-09-19 Richard Sandiford <rsandifo@nildram.co.uk>
* config/mips/mips.c (build_mips16_call_stub): Tidy. Fix second
diff --git a/gcc/dse.c b/gcc/dse.c
index 7a7afd7befc6c571f6df8c4ee99775b5706f866d..7bf759d45fc38f837d9a13d0f618cacaecab30c5 100644
--- a/gcc/dse.c
+++ b/gcc/dse.c
@@ -1399,6 +1399,7 @@ find_shift_sequence (rtx read_reg,
{
enum machine_mode store_mode = GET_MODE (store_info->mem);
enum machine_mode read_mode = GET_MODE (read_info->mem);
+ rtx chosen_seq = NULL;
/* Some machines like the x86 have shift insns for each size of
operand. Other machines like the ppc or the ia-64 may only have
@@ -1409,8 +1410,9 @@ find_shift_sequence (rtx read_reg,
for (; access_size < UNITS_PER_WORD; access_size *= 2)
{
- rtx target, new_reg;
+ rtx target, new_reg, shift_seq, insn;
enum machine_mode new_mode;
+ int cost;
/* Try a wider mode if truncating the store mode to ACCESS_SIZE
bytes requires a real instruction. */
@@ -1431,67 +1433,57 @@ find_shift_sequence (rtx read_reg,
target = expand_binop (new_mode, lshr_optab, new_reg,
GEN_INT (shift), new_reg, 1, OPTAB_DIRECT);
- if (target == new_reg)
- {
- rtx shift_seq = get_insns ();
- end_sequence ();
+ shift_seq = get_insns ();
+ end_sequence ();
- /* If cost is too great, set target to NULL and
- let the iteration happen. */
- if (shift_seq != NULL)
- {
- int cost = 0;
- rtx insn;
-
- for (insn = shift_seq; insn != NULL_RTX; insn = NEXT_INSN (insn))
- if (INSN_P (insn))
- cost += insn_rtx_cost (PATTERN (insn));
-
- /* The computation up to here is essentially independent
- of the arguments and could be precomputed. It may
- not be worth doing so. We could precompute if
- worthwhile or at least cache the results. The result
- technically depends on SHIFT, ACCESS_SIZE, and
- GET_MODE_CLASS (READ_MODE). But in practice the
- answer will depend only on ACCESS_SIZE. */
-
- if (cost <= COSTS_N_INSNS (1))
- {
- /* We found an acceptable shift. Generate a move to
- take the value from the store and put it into the
- shift pseudo, then shift it, then generate another
- move to put in into the target of the read. */
- start_sequence ();
- emit_move_insn (new_reg, gen_lowpart (new_mode, store_info->rhs));
- emit_insn (shift_seq);
- convert_move (read_reg, new_reg, 1);
+ if (target != new_reg || shift_seq == NULL)
+ continue;
+
+ cost = 0;
+ for (insn = shift_seq; insn != NULL_RTX; insn = NEXT_INSN (insn))
+ if (INSN_P (insn))
+ cost += insn_rtx_cost (PATTERN (insn));
+
+ /* The computation up to here is essentially independent
+ of the arguments and could be precomputed. It may
+ not be worth doing so. We could precompute if
+ worthwhile or at least cache the results. The result
+ technically depends on SHIFT, ACCESS_SIZE, and
+ GET_MODE_CLASS (READ_MODE). But in practice the
+ answer will depend only on ACCESS_SIZE. */
+
+ if (cost > COSTS_N_INSNS (1))
+ continue;
+
+ /* We found an acceptable shift. Generate a move to
+ take the value from the store and put it into the
+ shift pseudo, then shift it, then generate another
+ move to put in into the target of the read. */
+ start_sequence ();
+ emit_move_insn (new_reg, gen_lowpart (new_mode, store_info->rhs));
+ emit_insn (shift_seq);
+ convert_move (read_reg, new_reg, 1);
- if (dump_file)
- {
- fprintf (dump_file, " -- adding extract insn r%d:%s = r%d:%s\n",
- REGNO (new_reg), GET_MODE_NAME (new_mode),
- REGNO (store_info->rhs), GET_MODE_NAME (store_mode));
+ if (dump_file)
+ {
+ fprintf (dump_file, " -- adding extract insn r%d:%s = r%d:%s\n",
+ REGNO (new_reg), GET_MODE_NAME (new_mode),
+ REGNO (store_info->rhs), GET_MODE_NAME (store_mode));
- fprintf (dump_file, " -- with shift of r%d by %d\n",
- REGNO(new_reg), shift);
- fprintf (dump_file, " -- and second extract insn r%d:%s = r%d:%s\n",
- REGNO (read_reg), GET_MODE_NAME (read_mode),
- REGNO (new_reg), GET_MODE_NAME (new_mode));
- }
-
- /* Get the three insn sequence and return it. */
- shift_seq = get_insns ();
- end_sequence ();
- return shift_seq;
- }
- }
+ fprintf (dump_file, " -- with shift of r%d by %d\n",
+ REGNO(new_reg), shift);
+ fprintf (dump_file, " -- and second extract insn r%d:%s = r%d:%s\n",
+ REGNO (read_reg), GET_MODE_NAME (read_mode),
+ REGNO (new_reg), GET_MODE_NAME (new_mode));
}
- else
- /* End the sequence. */
- end_sequence ();
+
+ /* Get the three insn sequence and return it. */
+ chosen_seq = get_insns ();
+ end_sequence ();
+ break;
}
- return NULL;
+ return chosen_seq;
}