diff options
Diffstat (limited to 'gcc/loop.c')
| -rw-r--r-- | gcc/loop.c | 36 |
1 files changed, 21 insertions, 15 deletions
@@ -2451,11 +2451,9 @@ prescan_loop (loop) } /* Now, rescan the loop, setting up the LOOP_MEMS array. */ - if (/* We can't tell what MEMs are aliased by what. */ - ! unknown_address_altered - /* An exception thrown by a called function might land us + if (/* An exception thrown by a called function might land us anywhere. */ - && ! loop_info->has_call + ! loop_info->has_call /* We don't want loads for MEMs moved to a location before the one at which their stack memory becomes allocated. (Note that this is not a problem for malloc, etc., since those @@ -2467,6 +2465,23 @@ prescan_loop (loop) for (insn = NEXT_INSN (start); insn != NEXT_INSN (end); insn = NEXT_INSN (insn)) for_each_rtx (&insn, insert_loop_mem, 0); + + /* BLKmode MEMs are added to LOOP_STORE_MEM as necessary so + that loop_invariant_p and load_mems can use true_dependence + to determine what is really clobbered. */ + if (unknown_address_altered) + { + rtx mem = gen_rtx_MEM (BLKmode, const0_rtx); + + loop_store_mems = gen_rtx_EXPR_LIST (VOIDmode, mem, loop_store_mems); + } + if (unknown_constant_address_altered) + { + rtx mem = gen_rtx_MEM (BLKmode, const0_rtx); + + RTX_UNCHANGING_P (mem) = 1; + loop_store_mems = gen_rtx_EXPR_LIST (VOIDmode, mem, loop_store_mems); + } } /* LOOP->CONT_DOMINATOR is now the last label between the loop start @@ -3136,9 +3151,8 @@ note_set_pseudo_multiple_uses (x, y, data) The value is 2 if we refer to something only conditionally invariant. - If `unknown_address_altered' is nonzero, no memory ref is invariant. - Otherwise, a memory ref is invariant if it does not conflict with - anything stored in `loop_store_mems'. */ + A memory ref is invariant if it is not volatile and does not conflict + with anything stored in `loop_store_mems'. */ int loop_invariant_p (loop, x) @@ -3207,14 +3221,6 @@ loop_invariant_p (loop, x) if (MEM_VOLATILE_P (x)) return 0; - /* 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. */ mem_list_entry = loop_store_mems; while (mem_list_entry) |