diff options
Diffstat (limited to 'gcc/cselib.c')
| -rw-r--r-- | gcc/cselib.c | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/gcc/cselib.c b/gcc/cselib.c index 586b8cc..5a978c1 100644 --- a/gcc/cselib.c +++ b/gcc/cselib.c @@ -2502,6 +2502,7 @@ cselib_record_sets (rtx_insn *insn) rtx body = PATTERN (insn); rtx cond = 0; int n_sets_before_autoinc; + int n_strict_low_parts = 0; struct cselib_record_autoinc_data data; body = PATTERN (insn); @@ -2556,6 +2557,7 @@ cselib_record_sets (rtx_insn *insn) for (i = 0; i < n_sets; i++) { rtx dest = sets[i].dest; + rtx orig = dest; /* A STRICT_LOW_PART can be ignored; we'll record the equivalence for the low part after invalidating any knowledge about larger modes. */ @@ -2581,6 +2583,55 @@ cselib_record_sets (rtx_insn *insn) else sets[i].dest_addr_elt = 0; } + + /* Improve handling of STRICT_LOW_PART if the current value is known + to be const0_rtx, then the low bits will be set to dest and higher + bits will remain zero. Used in code like: + + {di:SI=0;clobber flags:CC;} + flags:CCNO=cmp(bx:SI,0) + strict_low_part(di:QI)=flags:CCNO<=0 + + where we can note both that di:QI=flags:CCNO<=0 and + also that because di:SI is known to be 0 and strict_low_part(di:QI) + preserves the upper bits that di:SI=zero_extend(flags:CCNO<=0). */ + scalar_int_mode mode; + if (dest != orig + && cselib_record_sets_hook + && REG_P (dest) + && HARD_REGISTER_P (dest) + && is_a <scalar_int_mode> (GET_MODE (dest), &mode) + && n_sets + n_strict_low_parts < MAX_SETS) + { + opt_scalar_int_mode wider_mode_iter; + FOR_EACH_WIDER_MODE (wider_mode_iter, mode) + { + scalar_int_mode wider_mode = wider_mode_iter.require (); + if (GET_MODE_PRECISION (wider_mode) > BITS_PER_WORD) + break; + + rtx reg = gen_lowpart (wider_mode, dest); + if (!REG_P (reg)) + break; + + cselib_val *v = cselib_lookup (reg, wider_mode, 0, VOIDmode); + if (!v) + continue; + + struct elt_loc_list *l; + for (l = v->locs; l; l = l->next) + if (l->loc == const0_rtx) + break; + + if (!l) + continue; + + sets[n_sets + n_strict_low_parts].dest = reg; + sets[n_sets + n_strict_low_parts].src = dest; + sets[n_sets + n_strict_low_parts++].src_elt = sets[i].src_elt; + break; + } + } } if (cselib_record_sets_hook) @@ -2625,6 +2676,20 @@ cselib_record_sets (rtx_insn *insn) || (MEM_P (dest) && cselib_record_memory)) cselib_record_set (dest, sets[i].src_elt, sets[i].dest_addr_elt); } + + /* And deal with STRICT_LOW_PART. */ + for (i = 0; i < n_strict_low_parts; i++) + { + if (! PRESERVED_VALUE_P (sets[n_sets + i].src_elt->val_rtx)) + continue; + machine_mode dest_mode = GET_MODE (sets[n_sets + i].dest); + cselib_val *v + = cselib_lookup (sets[n_sets + i].dest, dest_mode, 1, VOIDmode); + cselib_preserve_value (v); + rtx r = gen_rtx_ZERO_EXTEND (dest_mode, + sets[n_sets + i].src_elt->val_rtx); + cselib_add_permanent_equiv (v, r, insn); + } } /* Return true if INSN in the prologue initializes hard_frame_pointer_rtx. */ |