diff options
Diffstat (limited to 'gcc/loop.c')
| -rw-r--r-- | gcc/loop.c | 29 |
1 files changed, 26 insertions, 3 deletions
@@ -173,6 +173,9 @@ static char *moved_once; static rtx loop_store_mems; +/* The insn where the first of these was found. */ +static rtx first_loop_store_insn; + typedef struct loop_mem_info { rtx mem; /* The MEM itself. */ rtx reg; /* Corresponding pseudo, if any. */ @@ -2404,6 +2407,7 @@ prescan_loop (start, end) loop_has_volatile = 0; loop_has_tablejump = 0; loop_store_mems = NULL_RTX; + first_loop_store_insn = NULL_RTX; loop_mems_idx = 0; num_mem_sets = 0; @@ -2456,6 +2460,8 @@ prescan_loop (start, end) loop_has_tablejump = 1; note_stores (PATTERN (insn), note_addr_stored); + if (! first_loop_store_insn && loop_store_mems) + first_loop_store_insn = insn; if (! loop_has_multiple_exit_targets && GET_CODE (insn) == JUMP_INSN @@ -7682,9 +7688,26 @@ check_dbra_loop (loop_end, insn_count, loop_start, loop_info) case, the insn should have been moved out of the loop. */ if (num_mem_sets == 1) - reversible_mem_store - = (! unknown_address_altered - && ! invariant_p (XEXP (loop_store_mems, 0))); + { + struct induction *v; + + reversible_mem_store + = (! unknown_address_altered + && ! invariant_p (XEXP (loop_store_mems, 0))); + + /* If the store depends on a register that is set after the + store, it depends on the initial value, and is thus not + reversible. */ + for (v = bl->giv; reversible_mem_store && v; v = v->next_iv) + { + if (v->giv_type == DEST_REG + && reg_mentioned_p (v->dest_reg, + XEXP (loop_store_mems, 0)) + && (INSN_LUID (v->insn) + > INSN_LUID (first_loop_store_insn))) + reversible_mem_store = 0; + } + } } else return 0; |