2001-07-16 Daniel Berlin <dan@cgsoftware.com>
+ * gcse.c: Update comment at top.
+ Update comment on mem handling.
+ mem_last_set, mem_first_set, mem_set_in_block: gone.
+ Declaration of reg_set_info: gone.
+ (oprs_unchanged_p): Don't use mem_*set_* anymore. They are
+ pointless with load_killed_in_block_p (they are *more*
+ conservative then it, not less, and less accurate).
+ (oprs_not_set_p): Ditto.
+ (alloc_gcse_mem): Don't allocate mem_set_in_block
+ (free_gcse_mem): Don't free it, either.
+ (record_last_mem_set_info): Update comment in front, remove
+ mem_*set_* stuff. Note the reason we don't handle stores directly
+ here.
+ (compute_hash_table): Update comments to reflect reality. Remove
+ mem_*set_* references.
+ (reset_opr_set_tables): Remove mem_*set_* references.
+ (mark_call): Ditto.
+ (mark_set): Ditto. Also remove double sets of bitmaps for REG's.
+ (mark_clobber): Ditto (on both parts, we double set here too).
+ (expr_killed_p): Remove mem_set_in_block test.
+ (compute_transp): Remove mem_set_in_block test.
+
* ssa-ccp.c: (optimize_unexecutable_edges): Add note about removal
of edge, and removal of phi alternative to dump file.
(ssa_ccp_substitute_constants): Add note about register now being
- do rough calc of how many regs are needed in each block, and a rough
calc of how many regs are available in each class and use that to
throttle back the code in cases where RTX_COST is minimal.
- - dead store elimination
- a store to the same address as a load does not kill the load if the
source of the store is also the destination of the load. Handling this
allows more load motion, particularly out of loops.
/* This array parallels modify_mem_list, but is kept canonicalized. */
static rtx * canon_modify_mem_list;
-
-/* For each block, non-zero if memory is set in that block.
- This is computed during hash table computation and is used by
- expr_killed_p and compute_transp.
- ??? Handling of memory is very simple, we don't make any attempt
- to optimize things (later).
- ??? This can be computed by compute_sets since the information
- doesn't change. */
-static char *mem_set_in_block;
-
/* Various variables for statistics gathering. */
/* Memory used in a pass.
/* Allocate vars to track sets of regs, memory per block. */
reg_set_in_block = (sbitmap *) sbitmap_vector_alloc (n_basic_blocks,
max_gcse_regno);
- mem_set_in_block = (char *) gmalloc (n_basic_blocks);
/* Allocate array to keep a list of insns which modify memory in each
basic block. */
modify_mem_list = (rtx *) gmalloc (n_basic_blocks * sizeof (rtx *));
free (reg_set_bitmap);
sbitmap_vector_free (reg_set_in_block);
- free (mem_set_in_block);
/* re-Cache any INSN_LIST nodes we have allocated. */
{
int i;
static int *reg_first_set;
static int *reg_last_set;
-/* While computing "first/last set" info, this is the CUID of first/last insn
- to set memory or -1 if not set. `mem_last_set' is also used when
- performing GCSE to record whether memory has been set since the beginning
- of the block.
-
- Note that handling of memory is very simple, we don't make any attempt
- to optimize things (later). */
-static int mem_first_set;
-static int mem_last_set;
/* See whether X, the source of a set, is something we want to consider for
GCSE. */
if (load_killed_in_block_p (BLOCK_FOR_INSN (insn), INSN_CUID (insn),
x, avail_p))
return 0;
- if (avail_p && mem_last_set != NEVER_SET
- && mem_last_set >= INSN_CUID (insn))
- return 0;
- else if (! avail_p && mem_first_set != NEVER_SET
- && mem_first_set < INSN_CUID (insn))
- return 0;
else
return oprs_unchanged_p (XEXP (x, 0), insn, avail_p);
alloc_INSN_LIST (dest, canon_modify_mem_list[BLOCK_NUM (insn)]);
}
-/* Record memory first/last/block set information for INSN. */
/* Record memory modification information for INSN. We do not actually care
about the memory location(s) that are set, or even how they are set (consider
a CALL_INSN). We merely need to record which insns modify memory. */
record_last_mem_set_info (insn)
rtx insn;
{
- if (mem_first_set == NEVER_SET)
- mem_first_set = INSN_CUID (insn);
-
- mem_last_set = INSN_CUID (insn);
- mem_set_in_block[BLOCK_NUM (insn)] = 1;
+ /* load_killed_in_block_p will handle the case of calls clobbering
+ everything. */
modify_mem_list[BLOCK_NUM (insn)] =
alloc_INSN_LIST (insn, modify_mem_list[BLOCK_NUM (insn)]);
/* While we compute the hash table we also compute a bit array of which
registers are set in which blocks.
- We also compute which blocks set memory, in the absence of aliasing
- support [which is TODO].
??? This isn't needed during const/copy propagation, but it's cheap to
compute. Later. */
sbitmap_vector_zero (reg_set_in_block, n_basic_blocks);
- memset ((char *) mem_set_in_block, 0, n_basic_blocks);
/* re-Cache any INSN_LIST nodes we have allocated. */
{
/* First pass over the instructions records information used to
determine when registers and memory are first and last set.
- ??? The mem_set_in_block and hard-reg reg_set_in_block computation
+ ??? hard-reg reg_set_in_block computation
could be moved to compute_sets since they currently don't change. */
for (i = 0; i < max_gcse_regno; i++)
reg_first_set[i] = reg_last_set[i] = NEVER_SET;
- mem_first_set = NEVER_SET;
- mem_last_set = NEVER_SET;
for (insn = BLOCK_HEAD (bb);
insn && insn != NEXT_INSN (BLOCK_END (bb));
/* Also keep a record of the last instruction to modify memory.
For now this is very trivial, we only record whether any memory
location has been modified. */
- mem_last_set = 0;
{
int i;
if (load_killed_in_block_p (BLOCK_FOR_INSN (insn),
INSN_CUID (insn), x, 0))
return 0;
- if (mem_last_set != 0)
- return 0;
else
return oprs_not_set_p (XEXP (x, 0), insn);
mark_call (insn)
rtx insn;
{
- mem_last_set = INSN_CUID (insn);
if (! CONST_CALL_P (insn))
record_last_mem_set_info (insn);
}
else if (GET_CODE (dest) == MEM)
record_last_mem_set_info (insn);
- if (GET_CODE (dest) == REG)
- SET_BIT (reg_set_bitmap, REGNO (dest));
- else if (GET_CODE (dest) == MEM)
- mem_last_set = INSN_CUID (insn);
-
if (GET_CODE (SET_SRC (pat)) == CALL)
mark_call (insn);
}
if (GET_CODE (clob) == REG)
SET_BIT (reg_set_bitmap, REGNO (clob));
else
- mem_last_set = INSN_CUID (insn);
- if (GET_CODE (clob) == REG)
- SET_BIT (reg_set_bitmap, REGNO (clob));
- else
record_last_mem_set_info (insn);
}
case MEM:
if (load_killed_in_block_p (bb, get_max_uid () + 1, x, 0))
return 1;
- if (mem_set_in_block[bb->index])
- return 1;
else
return expr_killed_p (XEXP (x, 0), bb);
list_entry = XEXP (list_entry, 1);
}
}
- if (set_p)
- {
- for (bb = 0; bb < n_basic_blocks; bb++)
- if (mem_set_in_block[bb])
- SET_BIT (bmap[bb], indx);
- }
- else
- {
- for (bb = 0; bb < n_basic_blocks; bb++)
- if (mem_set_in_block[bb])
- RESET_BIT (bmap[bb], indx);
- }
x = XEXP (x, 0);
goto repeat;
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