On 2019-06-21 9:40 a.m., Richard Sandiford wrote:
ira_setup_alts has its own code to calculate the start of the constraint string for each operand/alternative combination, but preprocess_constraints now provides that information in (almost) constant time for non-asm instructions. Using it here should speed up the common case at the cost of potentially slowing down the handling of asm statements.
The documentation says that '%' should be the very first constraint character. But I think there is a possibility that somebody can forget this and put a blank before '%' and effect of this would be very hard to find as still the correct code would be generated although the code might be slower. That was my thoughts why I processed all constraint string.
It is hard to for me to say what the probability of this can be. I guess it is tiny. So the patch is ok for me.
The real reason for doing this is that a later patch wants to use more of the operand_alternative information. 2019-06-21 Richard Sandiford <richard.sandif...@arm.com> gcc/ * ira.c (ira_setup_alts): Use preprocess_constraints to get the constraint string for each operand/alternative combo. Only handle '%' at the start of constraint strings, and look for it outside the main loop. Index: gcc/ira.c =================================================================== --- gcc/ira.c 2019-06-21 14:34:05.887715020 +0100 +++ gcc/ira.c 2019-06-21 14:34:09.455685354 +0100 @@ -1791,60 +1791,42 @@ setup_prohibited_mode_move_regs (void) alternative_mask ira_setup_alts (rtx_insn *insn) { - /* MAP nalt * nop -> start of constraints for given operand and - alternative. */ - static vec<const char *> insn_constraints; int nop, nalt; bool curr_swapped; const char *p; int commutative = -1;extract_insn (insn);+ preprocess_constraints (insn); alternative_mask preferred = get_preferred_alternatives (insn); alternative_mask alts = 0; - insn_constraints.release (); - insn_constraints.safe_grow_cleared (recog_data.n_operands - * recog_data.n_alternatives + 1); /* Check that the hard reg set is enough for holding all alternatives. It is hard to imagine the situation when the assertion is wrong. */ ira_assert (recog_data.n_alternatives <= (int) MAX (sizeof (HARD_REG_ELT_TYPE) * CHAR_BIT, FIRST_PSEUDO_REGISTER)); + for (nop = 0; nop < recog_data.n_operands; nop++) + if (recog_data.constraints[nop][0] == '%') + { + commutative = nop; + break; + } for (curr_swapped = false;; curr_swapped = true) { - /* Calculate some data common for all alternatives to speed up the - function. */ - for (nop = 0; nop < recog_data.n_operands; nop++) - { - for (nalt = 0, p = recog_data.constraints[nop]; - nalt < recog_data.n_alternatives; - nalt++) - { - insn_constraints[nop * recog_data.n_alternatives + nalt] = p; - while (*p && *p != ',') - { - /* We only support one commutative marker, the first - one. We already set commutative above. */ - if (*p == '%' && commutative < 0) - commutative = nop; - p++; - } - if (*p) - p++; - } - } for (nalt = 0; nalt < recog_data.n_alternatives; nalt++) { if (!TEST_BIT (preferred, nalt) || TEST_BIT (alts, nalt)) continue;+ const operand_alternative *op_alt+ = &recog_op_alt[nalt * recog_data.n_operands]; for (nop = 0; nop < recog_data.n_operands; nop++) { int c, len;rtx op = recog_data.operand[nop];- p = insn_constraints[nop * recog_data.n_alternatives + nalt]; + p = op_alt[nop].constraint; if (*p == 0 || *p == ',') continue;
