diff options
Diffstat (limited to 'gcc/loop.c')
| -rw-r--r-- | gcc/loop.c | 46 |
1 files changed, 25 insertions, 21 deletions
@@ -197,6 +197,11 @@ static int loop_mems_allocated; static int unknown_address_altered; +/* The above doesn't count any readonly memory locations that are stored. + This does. */ + +static int unknown_constant_address_altered; + /* Count of movable (i.e. invariant) instructions discovered in the loop. */ static int num_movables; @@ -2386,9 +2391,9 @@ constant_high_bytes (p, loop_start) /* Scan a loop setting the elements `cont', `vtop', `loops_enclosed', `has_call', `has_volatile', and `has_tablejump' within LOOP_INFO. - Set the global variables `unknown_address_altered' and - `num_mem_sets'. Also, fill in the array `loop_mems' and the list - `loop_store_mems'. */ + Set the global variables `unknown_address_altered', + `unknown_constant_address_altered', and `num_mem_sets'. Also, fill + in the array `loop_mems' and the list `loop_store_mems'. */ static void prescan_loop (start, end, loop_info) @@ -2414,6 +2419,7 @@ prescan_loop (start, end, loop_info) loop_info->vtop = 0; unknown_address_altered = 0; + unknown_constant_address_altered = 0; loop_store_mems = NULL_RTX; first_loop_store_insn = NULL_RTX; loop_mems_idx = 0; @@ -3166,11 +3172,15 @@ note_addr_stored (x, y, data) num_mem_sets++; /* BLKmode MEM means all memory is clobbered. */ - if (GET_MODE (x) == BLKmode) - unknown_address_altered = 1; + if (GET_MODE (x) == BLKmode) + { + if (RTX_UNCHANGING_P (x)) + unknown_constant_address_altered = 1; + else + unknown_address_altered = 1; - if (unknown_address_altered) - return; + return; + } loop_store_mems = gen_rtx_EXPR_LIST (VOIDmode, x, loop_store_mems); } @@ -3275,20 +3285,12 @@ invariant_p (x) return VARRAY_INT (set_in_loop, REGNO (x)) == 0; case MEM: - /* Volatile memory references must be rejected. Do this before - checking for read-only items, so that volatile read-only items - will be rejected also. */ - if (MEM_VOLATILE_P (x)) - return 0; - - /* Read-only items (such as constants in a constant pool) are - invariant if their address is. */ - if (RTX_UNCHANGING_P (x)) - break; - - /* If we had a subroutine call, any location in memory could have been - clobbered. */ - if (unknown_address_altered) + /* If we had a subroutine call, any location in memory could + have been clobbered. We used to test here for volatile and + readonly, but true_dependence knows how to do that better + than we do. */ + if (RTX_UNCHANGING_P (x) + ? unknown_constant_address_altered : unknown_address_altered) return 0; /* See if there is any dependence between a store and this load. */ @@ -3298,6 +3300,7 @@ invariant_p (x) if (true_dependence (XEXP (mem_list_entry, 0), VOIDmode, x, rtx_varies_p)) return 0; + mem_list_entry = XEXP (mem_list_entry, 1); } @@ -8013,6 +8016,7 @@ check_dbra_loop (loop_end, insn_count, loop_start, loop_info) reversible_mem_store = (! unknown_address_altered + && ! unknown_constant_address_altered && ! invariant_p (XEXP (XEXP (loop_store_mems, 0), 0))); /* If the store depends on a register that is set after the |