void find_comparison_dom_walker::before_dom_children (basic_block bb) { struct comparison *last_cmp; rtx_insn *insn, *next, *last_clobber; bool last_cmp_valid; bool need_purge = false; bitmap killed; killed = BITMAP_ALLOC (NULL); /* The last comparison that was made. Will be reset to NULL once the flags are clobbered. */ last_cmp = NULL; /* True iff the last comparison has not been clobbered, nor have its inputs. Used to eliminate duplicate compares. */ last_cmp_valid = false; /* The last insn that clobbered the flags, if that insn is of a form that may be valid for eliminating a following compare. To be reset to NULL once the flags are set otherwise. */ last_clobber = NULL; /* Propagate the last live comparison throughout the extended basic block. */ if (single_pred_p (bb)) { last_cmp = (struct comparison *) single_pred (bb)->aux; if (last_cmp) last_cmp_valid = last_cmp->inputs_valid; } for (insn = BB_HEAD (bb); insn; insn = next) { rtx src; next = (insn == BB_END (bb) ? NULL : NEXT_INSN (insn)); if (!NONDEBUG_INSN_P (insn)) continue; /* Compute the set of registers modified by this instruction. */ bitmap_clear (killed); df_simulate_find_defs (insn, killed); src = conforming_compare (insn); if (src) { rtx eh_note = NULL; if (cfun->can_throw_non_call_exceptions) eh_note = find_reg_note (insn, REG_EH_REGION, NULL); if (last_cmp_valid && can_eliminate_compare (src, eh_note, last_cmp)) { if (eh_note) need_purge = true; delete_insn (insn); continue; } last_cmp = XCNEW (struct comparison); last_cmp->insn = insn; last_cmp->prev_clobber = last_clobber; last_cmp->in_a = XEXP (src, 0); last_cmp->in_b = XEXP (src, 1); last_cmp->eh_note = eh_note; last_cmp->orig_mode = GET_MODE (src); all_compares.safe_push (last_cmp); /* It's unusual, but be prepared for comparison patterns that also clobber an input, or perhaps a scratch. */ last_clobber = NULL; last_cmp_valid = true; } /* Notice if this instruction kills the flags register. */ else if (bitmap_bit_p (killed, targetm.flags_regnum)) { /* See if this insn could be the "clobber" that eliminates a future comparison. */ last_clobber = (arithmetic_flags_clobber_p (insn) ? insn : NULL); /* In either case, the previous compare is no longer valid. */ last_cmp = NULL; last_cmp_valid = false; } /* Notice if this instruction uses the flags register. */ else if (last_cmp) find_flags_uses_in_insn (last_cmp, insn); /* Notice if any of the inputs to the comparison have changed. */ if (last_cmp_valid && (bitmap_bit_p (killed, REGNO (last_cmp->in_a)) || (REG_P (last_cmp->in_b) && bitmap_bit_p (killed, REGNO (last_cmp->in_b))))) last_cmp_valid = false; }
void find_comparison_dom_walker::before_dom_children (basic_block bb) { struct comparison *last_cmp; rtx insn, next, last_clobber; bool last_cmp_valid; bool need_purge = false; bitmap killed; killed = BITMAP_ALLOC (NULL); /* The last comparison that was made. Will be reset to NULL once the flags are clobbered. */ last_cmp = NULL; /* True iff the last comparison has not been clobbered, nor have its inputs. Used to eliminate duplicate compares. */ last_cmp_valid = false; /* The last insn that clobbered the flags, if that insn is of a form that may be valid for eliminating a following compare. To be reset to NULL once the flags are set otherwise. */ last_clobber = NULL; /* Propagate the last live comparison throughout the extended basic block. */ if (single_pred_p (bb)) { last_cmp = (struct comparison *) single_pred (bb)->aux; if (last_cmp) last_cmp_valid = last_cmp->inputs_valid; } for (insn = BB_HEAD (bb); insn; insn = next) { rtx src; next = (insn == BB_END (bb) ? NULL_RTX : NEXT_INSN (insn)); if (!NONDEBUG_INSN_P (insn)) continue; /* Compute the set of registers modified by this instruction. */ bitmap_clear (killed); df_simulate_find_defs (insn, killed); src = conforming_compare (insn); if (src) { enum machine_mode src_mode = GET_MODE (src); rtx eh_note = NULL; if (flag_non_call_exceptions) eh_note = find_reg_note (insn, REG_EH_REGION, NULL); if (!last_cmp_valid) goto dont_delete; /* Take care that it's in the same EH region. */ if (flag_non_call_exceptions && !rtx_equal_p (eh_note, last_cmp->eh_note)) goto dont_delete; /* Make sure the compare is redundant with the previous. */ if (!rtx_equal_p (last_cmp->in_a, XEXP (src, 0)) || !rtx_equal_p (last_cmp->in_b, XEXP (src, 1))) goto dont_delete; /* New mode must be compatible with the previous compare mode. */ { enum machine_mode new_mode = targetm.cc_modes_compatible (last_cmp->orig_mode, src_mode); if (new_mode == VOIDmode) goto dont_delete; if (new_mode != last_cmp->orig_mode) { rtx x, flags = gen_rtx_REG (src_mode, targetm.flags_regnum); /* Generate new comparison for substitution. */ x = gen_rtx_COMPARE (new_mode, XEXP (src, 0), XEXP (src, 1)); x = gen_rtx_SET (VOIDmode, flags, x); if (!validate_change (last_cmp->insn, &PATTERN (last_cmp->insn), x, false)) goto dont_delete; last_cmp->orig_mode = new_mode; } } /* All tests and substitutions succeeded! */ if (eh_note) need_purge = true; delete_insn (insn); continue; dont_delete: last_cmp = XCNEW (struct comparison); last_cmp->insn = insn; last_cmp->prev_clobber = last_clobber; last_cmp->in_a = XEXP (src, 0); last_cmp->in_b = XEXP (src, 1); last_cmp->eh_note = eh_note; last_cmp->orig_mode = src_mode; all_compares.safe_push (last_cmp); /* It's unusual, but be prepared for comparison patterns that also clobber an input, or perhaps a scratch. */ last_clobber = NULL; last_cmp_valid = true; } /* Notice if this instruction kills the flags register. */ else if (bitmap_bit_p (killed, targetm.flags_regnum)) { /* See if this insn could be the "clobber" that eliminates a future comparison. */ last_clobber = (arithmetic_flags_clobber_p (insn) ? insn : NULL); /* In either case, the previous compare is no longer valid. */ last_cmp = NULL; last_cmp_valid = false; continue; } /* Notice if this instruction uses the flags register. */ else if (last_cmp) find_flags_uses_in_insn (last_cmp, insn); /* Notice if any of the inputs to the comparison have changed. */ if (last_cmp_valid && (bitmap_bit_p (killed, REGNO (last_cmp->in_a)) || (REG_P (last_cmp->in_b) && bitmap_bit_p (killed, REGNO (last_cmp->in_b))))) last_cmp_valid = false; }