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author | Richard Sandiford <rsandifo@nildram.co.uk> | 2007-09-16 21:02:54 +0000 |
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committer | Richard Sandiford <rsandifo@gcc.gnu.org> | 2007-09-16 21:02:54 +0000 |
commit | 348eea5f00fe47fa13c235e9e93c082b8b285f97 (patch) | |
tree | 24f70bdc3e262c76611c228272c31e27b2f21f85 /gcc/dse.c | |
parent | 0ee3f0a892918371a5245de973480bc443126558 (diff) | |
download | gcc-348eea5f00fe47fa13c235e9e93c082b8b285f97.zip gcc-348eea5f00fe47fa13c235e9e93c082b8b285f97.tar.gz gcc-348eea5f00fe47fa13c235e9e93c082b8b285f97.tar.bz2 |
dse.c (find_shift_sequence): Allow word as well as subword shifts.
gcc/
* dse.c (find_shift_sequence): Allow word as well as subword shifts.
Do the tentative shift expansion with the DF_NO_INSN_RESCAN flag set.
Fix the call to insn_rtx_cost. Skip access sizes that require a
real truncation of the store register. Use convert_move instead
of gen_lowpart when narrowing the result.
(replace_read): Use convert_move instead of gen_lowpart when
narrowing the store rhs.
gcc/testsuite/
* gcc.target/mips/dse-1.c: New test.
From-SVN: r128530
Diffstat (limited to 'gcc/dse.c')
-rw-r--r-- | gcc/dse.c | 31 |
1 files changed, 20 insertions, 11 deletions
@@ -1407,21 +1407,31 @@ find_shift_sequence (rtx read_reg, justify the value we want to read but is available in one insn on the machine. */ - while (access_size < UNITS_PER_WORD) + for (; access_size <= UNITS_PER_WORD; access_size *= 2) { - rtx target; - enum machine_mode new_mode - = smallest_mode_for_size (access_size * BITS_PER_UNIT, - GET_MODE_CLASS (read_mode)); - rtx new_reg = gen_reg_rtx (new_mode); + rtx target, new_reg; + enum machine_mode new_mode; + + /* Try a wider mode if truncating the store mode to ACCESS_SIZE + bytes requires a real instruction. */ + if (access_size < GET_MODE_SIZE (store_mode) + && !TRULY_NOOP_TRUNCATION (access_size * BITS_PER_UNIT, + GET_MODE_BITSIZE (store_mode))) + continue; + + new_mode = smallest_mode_for_size (access_size * BITS_PER_UNIT, + GET_MODE_CLASS (read_mode)); + new_reg = gen_reg_rtx (new_mode); start_sequence (); /* In theory we could also check for an ashr. Ian Taylor knows of one dsp where the cost of these two was not the same. But this really is a rare case anyway. */ + df_set_flags (DF_NO_INSN_RESCAN); target = expand_binop (new_mode, lshr_optab, new_reg, GEN_INT (shift), new_reg, 1, OPTAB_DIRECT); + df_clear_flags (DF_NO_INSN_RESCAN); if (target == new_reg) { @@ -1436,7 +1446,8 @@ find_shift_sequence (rtx read_reg, rtx insn; for (insn = shift_seq; insn != NULL_RTX; insn = NEXT_INSN (insn)) - cost += insn_rtx_cost (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 @@ -1455,7 +1466,7 @@ find_shift_sequence (rtx read_reg, start_sequence (); emit_move_insn (new_reg, gen_lowpart (new_mode, store_info->rhs)); emit_insn (shift_seq); - emit_move_insn (read_reg, gen_lowpart (read_mode, new_reg)); + convert_move (read_reg, new_reg, 1); if (dump_file) { @@ -1480,8 +1491,6 @@ find_shift_sequence (rtx read_reg, else /* End the sequence. */ end_sequence (); - - access_size = access_size * 2; } return NULL; @@ -1595,7 +1604,7 @@ replace_read (store_info_t store_info, insn_info_t store_insn, place, we need to extract the value in the right from the rhs of the store. */ start_sequence (); - emit_move_insn (read_reg, gen_lowpart (read_mode, store_info->rhs)); + convert_move (read_reg, store_info->rhs, 1); if (dump_file) fprintf (dump_file, " -- adding extract insn r%d:%s = r%d:%s\n", |