opt.c

#include "9cc.h"

static void opt(IR *ir) {
    if (ir->op == IR_BPREL) {
        Var *var = ir->var;
        if (var->address_taken || var->ty->ty != INT) {
            return;
        }
        if (!var->promoted) {
            var->promoted = new_reg();
        }
        ir->op = IR_NOP;
        ir->r0->promoted = var->promoted;
        return;
    }

    if (ir->op == IR_LOAD) {
        if (!ir->r2->promoted) {
            return;
        }
        ir->op = IR_MOV;
        ir->r2 = ir->r2->promoted;
        return;
    }

    if (ir->op == IR_STORE) {
        if (!ir->r1->promoted) {
            return;
        }
        ir->op = IR_MOV;
        ir->r0 = ir->r1->promoted;
        ir->r1 = NULL;
        return;
    }
}

void optimize(Program *prog) {
    for (int i = 0; i < prog->funcs->len; i++) {
        Function *fn = prog->funcs->data[i];

        for (int i = 0; i < fn->bbs->len; i++) {
            BB *bb = fn->bbs->data[i];

            for (int i = 0; i < bb->ir->len; i++) {
                opt(bb->ir->data[i]);
            }
        }
    }
}