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(memory_extend_rtx): New variable. 

(cse_main): Initialize it.
(cse_insn): See if we have already loaded a MEM in a wider  mode.

From-SVN: r6484
This commit is contained in:
Richard Kenner 1994-02-05 08:05:42 -05:00
parent 17a08984d3
commit 7bac1be089
1 changed files with 60 additions and 1 deletions
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61
gcc/cse.c
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@ -348,6 +348,12 @@ static int cse_jumps_altered;
static int do_not_record;
#ifdef LOAD_EXTEND_OP
/* Scratch rtl used when looking for load-extended copy of a MEM. */
static rtx memory_extend_rtx;
#endif
/* canon_hash stores 1 in hash_arg_in_memory
if it notices a reference to memory within the expression being hashed. */
@ -6378,7 +6384,53 @@ cse_insn (insn, in_libcall_block)
}
}
}
#ifdef LOAD_EXTEND_OP
/* See if a MEM has already been loaded with a widening operation;
if it has, we can use a subreg of that. Many CISC machines
also have such operations, but this is only likely to be
beneficial these machines. */
if (flag_expensive_optimizations && src_related == 0
&& (GET_MODE_SIZE (mode) < UNITS_PER_WORD)
&& GET_MODE_CLASS (mode) == MODE_INT
&& GET_CODE (src) == MEM && ! do_not_record
&& LOAD_EXTEND_OP (mode) != NIL)
{
enum machine_mode tmode;
/* Set what we are trying to extend and the operation it might
have been extended with. */
PUT_CODE (memory_extend_rtx, LOAD_EXTEND_OP (mode));
XEXP (memory_extend_rtx, 0) = src;
for (tmode = GET_MODE_WIDER_MODE (mode);
GET_MODE_SIZE (tmode) <= UNITS_PER_WORD;
tmode = GET_MODE_WIDER_MODE (tmode))
{
struct table_elt *larger_elt;
PUT_MODE (memory_extend_rtx, tmode);
larger_elt = lookup (memory_extend_rtx,
HASH (memory_extend_rtx, tmode), tmode);
if (larger_elt == 0)
continue;
for (larger_elt = larger_elt->first_same_value;
larger_elt; larger_elt = larger_elt->next_same_value)
if (GET_CODE (larger_elt->exp) == REG)
{
src_related = gen_lowpart_if_possible (mode,
larger_elt->exp);
break;
}
if (src_related)
break;
}
}
#endif /* LOAD_EXTEND_OP */
if (src == src_folded)
src_folded = 0;
@ -7916,6 +7968,13 @@ cse_main (f, nregs, after_loop, file)
reg_in_table = (int *) alloca (nregs * sizeof (int));
reg_tick = (int *) alloca (nregs * sizeof (int));
#ifdef LOAD_EXTEND_OP
/* Allocate scratch rtl here. cse_insn will fill in the memory reference
and change the code and mode as appropriate. */
memory_extend_rtx = gen_rtx (ZERO_EXTEND, VOIDmode, 0);
#endif
/* Discard all the free elements of the previous function
since they are allocated in the temporarily obstack. */
bzero (table, sizeof table);