peep68.c

一个c compiler的source code

        if( ap1->mode != ap2->mode )
                return 0;
        switch( ap1->mode )
                {
                case am_areg:   case am_dreg:
                case am_ainc:   case am_adec:
                        return ap1->preg == ap2->preg;
								case am_baseindxaddr:
								case am_baseindxdata:
								case am_indx:
												if (ap1->preg != ap2->preg)
													return FALSE;
												if (ap1->sreg != ap2->sreg)
													return FALSE;
												return equalnode(ap1->offset,ap2->offset);
								case am_immed:
								case am_direct:
								case am_adirect:
								case am_pcindx:
												return equalnode(ap1->offset,ap2->offset);
                }
        return 0;
}

void peep_add(OCODE *ip)
/*
 *      peephole optimization for add instructions.
 *      makes quick immediates out of small constants.
 */
{       ENODE    *ep;
				if (ip->noopt)
					return;
				if (ip->oper2->mode == am_areg)
					ip->opcode = op_adda;
        if( ip->oper1->mode != am_immed )
                return;
        ep = ip->oper1->offset;
        if( ip->oper2->mode != am_areg )
                ip->opcode = op_addi;
        else
                {
                if( isshort(ep) )
                        ip->length = 2;
                }
        if( !(isintconst(ep->nodetype)))
                return;
        if( 1 <= ep->v.i && ep->v.i <= 8 )
                ip->opcode = op_addq;
        else if( -8 <= ep->v.i && ep->v.i <= -1 )
                {
                ip->opcode = op_subq;
                ep->v.i = -ep->v.i;
                }
}

void peep_sub(OCODE *ip)
/*
 *      peephole optimization for subtract instructions.
 *      makes quick immediates out of small constants.
 */
{       ENODE    *ep;
				if (ip->noopt)
					return;
				if (ip->oper2->mode == am_areg)
					ip->opcode = op_suba;
        if( ip->oper1->mode != am_immed )
                return;
        ep = ip->oper1->offset;
        if( ip->oper2->mode != am_areg )
                ip->opcode = op_subi;
        else
                {
                if( isshort(ep) )
                        ip->length = 2;
                }
        if(!isintconst( ep->nodetype) )
                return;
        if( 1 <= ep->v.i && ep->v.i <= 8 ) {
                ip->opcode = op_subq;
								if (ip->oper2->mode == am_areg && ip->length <=4 && ip->fwd->oper1->mode == am_ind && ip->oper2->preg == ip->fwd->oper1->preg) {
									int sz1 = ip->fwd->length;
									int sz2 = ep->v.i;
									if (sz1 < 0) sz1 = -sz1;
									if (sz2 < 0) sz2 = -sz2;
									if (sz2 == sz1) {
										ip->back->fwd = ip->fwd;
										ip->fwd->back = ip->back;
										ip->fwd->oper1->mode = am_adec;
									}
								}
				}
        else if( -8 <= ep->v.i && ep->v.i <= -1 )
                {
                ip->opcode = op_addq;
                ep->v.i = -ep->v.i;
                }
}
void     peep_cmp(OCODE *ip)
/*
 *      peephole optimization for compare instructions.
 *      changes compare #0 to tst and if previous instruction
 *      should have set the condition codes properly delete.
 *      return value is true if instruction was deleted.
 */
{       OCODE    *prev=0;
        ENODE    *ep;
				if (ip->noopt)
					return;
				if (ip->oper2->mode == am_areg)
					ip->opcode = op_cmpa;
        if( ip->oper1->mode == am_immed ) {
	        ep = ip->oper1->offset;
  	      if( ip->oper2->mode == am_areg )
    	            {
      	          if( isshort(ep) )
        	                ip->length = 2;
          	      return;
            	    }
	        ip->opcode = op_cmpi;
  	      if( isintconst(ep->nodetype) &&  ep->v.i == 0 ) {
						if (ip->fwd->opcode == op_bne || ip->fwd->opcode == op_beq ) {
			        ip->oper1 = ip->oper2;
  	  	  	  ip->oper2 = 0;
    	  	  	ip->opcode = op_tst;
		  	      prev = ip->back;
						}
					}
				}
    		if( prev == 0)
                return;
        if( (((prev->opcode == op_move || prev->opcode == op_moveq
							|| prev->opcode == op_add || prev->opcode == op_addi
							|| prev->opcode == op_sub || prev->opcode == op_subi
							|| prev->opcode == op_addq || prev->opcode == op_subq) &&
              equal_address(prev->oper1,ip->oper1)) &&
                prev->oper2->mode != am_areg) ||
                (prev->opcode != op_label &&
                equal_address(prev->oper2,ip->oper1)) )
                {
                prev->fwd = ip->fwd;
                if( prev->fwd != 0 )
                        prev->fwd->back = prev;
                }
}

void peep_muldiv(OCODE *ip, int op)
/*
 *      changes multiplies and divides by convienient values
 *      to shift operations. op should be either op_asl or
 *      op_asr (for divide).
 */
{       int     shcnt;
				if (ip->noopt)
					return;
        if( ip->oper1->mode != am_immed )
                return;
        if(!isintconst( ip->oper1->offset->nodetype ))
                return;
        shcnt = ip->oper1->offset->v.i;
/*      vax c doesn't do this type of switch well       */
        if( shcnt == 2) shcnt = 1;
        else if( shcnt == 4) shcnt = 2;
        else if( shcnt == 8) shcnt = 3;
        else if( shcnt == 16) shcnt = 4;
        else if( shcnt == 32) shcnt = 5;
        else if( shcnt == 64) shcnt = 6;
        else if( shcnt == 128) shcnt = 7;
        else if( shcnt == 256) shcnt = 8;
        else if( shcnt == 512) shcnt = 9;
        else if( shcnt == 1024) shcnt = 10;
        else if( shcnt == 2048) shcnt = 11;
        else if( shcnt == 4096) shcnt = 12;
        else if( shcnt == 8192) shcnt = 13;
        else if( shcnt == 16384) shcnt = 14;
        else return;
        ip->oper1->offset->v.i = shcnt;
        ip->opcode = op;
        ip->length = 4;
}

void peep_uctran(OCODE *ip)
/*
 *      peephole optimization for unconditional transfers.
 *      deletes instructions which have no path.
 *      applies to bra, jmp, and rts instructions.
 */
{       while( ip->fwd != 0 && ip->fwd->opcode != op_label )
                {
                ip->fwd = ip->fwd->fwd;
                if( ip->fwd != 0 )
                        ip->fwd->back = ip;
                }
}
void peep_label(OCODE *ip)
/*
 *		peephole optimization for labels
 *		deletes relbranches that jump to the next instruction
 */
{
			OCODE *curpos, *index;
			curpos = ip;

			if (!curpos->back)
				return;
			do {
				curpos = curpos->back;
			} while(curpos->opcode == op_label || curpos->opcode == op_line);
			while ((curpos->opcode == op_bra) || curpos->opcode == op_cmp
						|| curpos->opcode == op_cmpi || curpos->opcode == op_tst 
						|| (curpos->opcode == op_bne) || (curpos->opcode == op_beq) 
						|| (curpos->opcode == op_bge) || (curpos->opcode == op_ble) 
						|| (curpos->opcode == op_bgt) || (curpos->opcode == op_blt) 
						|| (curpos->opcode == op_bhs) || (curpos->opcode == op_bls) 
						|| (curpos->opcode == op_bhi) || (curpos->opcode == op_blo) ) {
				index = curpos->fwd;
				if (ip->noopt)
					return;
				if ((curpos->opcode == op_cmpi || curpos->opcode == op_cmp
								|| curpos->opcode == op_tst )) {
					if (curpos->fwd->opcode == op_label) {
						curpos->back->fwd = curpos->fwd;
						curpos->fwd->back = curpos->back;
						curpos = curpos->back;
					}
					else
						break;
				}
				else {
					do {
						if ((index->opcode == op_label) && (curpos->oper1->mode == am_direct) && ((int)index->oper1 == curpos->oper1->offset->v.i)) {
							curpos->back->fwd = curpos->fwd;
							curpos->fwd->back = curpos->back;
							curpos = curpos->back;
							break;
						}
						index = index->fwd;
					} while (index != ip->fwd);
					if (index == ip->fwd)
						break;
				}
				while(curpos->opcode == op_label || curpos->opcode == op_line)
					curpos = curpos->back;
			}
}

void opt3(void)
/*
 *      peephole optimizer. This routine calls the instruction
 *      specific optimization routines above for each instruction
 *      in the peep list.
 */
{       OCODE    *ip=peep_head;
        while( ip != 0 )
                {
								if (ip->opcode != op_line && ip->opcode != op_label && ip->opcode != op_slit) {
									if (ip->oper1 && ip->oper1->mode == am_indx && ip->oper1->offset->v.i == 0)
										ip->oper1->mode = am_ind;
									if (ip->oper2 && ip->oper2->mode == am_indx && ip->oper2->offset->v.i == 0)
										ip->oper2->mode = am_ind;
								}
                switch( ip->opcode )
                        {
                        case op_move:
                                peep_move(ip);
                                break;
                        case op_add:
                                peep_add(ip);
                                break;
                        case op_sub:
                                peep_sub(ip);
                                break;
												case op_tst:
																peep_tst(ip);
																break;
                        case op_cmp:
                                peep_cmp(ip);
                                break;
												case op_and:
																if (ip->oper1->mode == am_immed)
																	ip->opcode = op_andi;
																break;
												case op_or:
																if (ip->oper1->mode == am_immed)
																	ip->opcode = op_ori;
																break;
												case op_eor:
																if (ip->oper1->mode == am_immed)
																	ip->opcode = op_eori;
																break;
                        case op_muls:
                                peep_muldiv(ip,op_asl);
                                break;
												case op_label:
																peep_label(ip);
																break;
                        case op_bra:
                        case op_jmp:
                        case op_rts:
                                peep_uctran(ip);
                        }
                ip = ip->fwd;
                }
}