/*****
* stm.cc
* Andy Hammerlindl 2002/8/30
*
* Statements are everything in the language that do something on their
* own.  Statements are different from declarations in that statements
* do not modify the environment.  Translation of a statement puts the
* stack code to run it into the instruction stream.
*****/

#include <fstream>
#include "errormsg.h"
#include "settings.h"
#include "coenv.h"
#include "exp.h"
#include "stm.h"

#include "symbol.h"
#include "opsymbols.h"

namespace absyntax {

using namespace trans;
using namespace types;

void stm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"stm",indent, getPos());
}


void emptyStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"emptyStm",indent, getPos());
}


void blockStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"blockStm",indent, getPos());

 base->prettyprint(out, indent+1);
}



void expStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"expStm",indent, getPos());

 body->prettyprint(out, indent+1);
}

void baseExpTrans(coenv &e, exp *expr)
{
 types::ty_kind kind = expr->trans(e)->kind;
 if (kind != types::ty_void)
   // Remove any value it puts on the stack.
   e.c.encodePop();
}

void expStm::trans(coenv &e) {
 baseExpTrans(e, body);
}

// For an object such as currentpicture, write 'picture currentpicture' to
// give some information.  Only do this when the object has a name.
void tryToWriteTypeOfExp(types::ty *t, exp *body)
{
 symbol name=body->getName();
 if (!name)
   return;

 overloaded *set = dynamic_cast<overloaded *>(t);
 if (set)
   for(ty_vector::iterator ot=set->sub.begin(); ot!=set->sub.end(); ++ot)
     tryToWriteTypeOfExp(*ot, body);
 else {
   cout << "<";
   t->printVar(cout, name);
   cout << ">" << endl;
 }
}

// From dec.cc:
varEntry *makeVarEntry(position pos, coenv &e, record *r, types::ty *t);

void storeExp(coenv &e, types::ty *t, exp *expr) {
 assert(t->kind != ty_error);
 assert(t->kind != ty_void);
 assert(t->kind != ty_overloaded);

 expr->transAsType(e, t);

 // Store the value in a new variable of the proper type.
 varEntry *v = makeVarEntry(expr->getPos(), e, 0, t);
 e.e.addVar(symbol::trans("operator answer"), v);
 v->getLocation()->encode(WRITE, expr->getPos(), e.c);
 e.c.encodePop();
}

void storeAndWriteExp(coenv &e, types::ty *t, exp *expr) {
 storeExp(e, t, expr);

 position pos=expr->getPos();
 baseExpTrans(e, new callExp(pos, new nameExp(pos, "write"),
                             new nameExp(pos, "operator answer")));
}

void tryToWriteExp(coenv &e, exp *expr)
{
 position pos=expr->getPos();
 types::ty *t=expr->cgetType(e);

 if(!t) return;

 // If the original expression is bad, just print the errors.
 // If it is a function which returns void, just call the function.
 if (t->kind == ty_error || t->kind == ty_void) {
   baseExpTrans(e, expr);
   return;
 }

 exp *callee=new nameExp(pos, symbol::trans("write"));
 exp *call=new callExp(pos, callee, expr);

 types::ty *ct=call->getType(e);
 if (ct->kind == ty_error || ct->kind == ty_overloaded) {
   if (t->kind == ty_overloaded) {
     // Translate the expr in order to print the ambiguity error first.
     expr->trans(e);
     em.sync(true);
     assert(em.errors());

     // Then, write out all of the types.
     tryToWriteTypeOfExp(t, expr);
   }
   else {
     // Write the type of the expression and, since it is unique, assign it to
     // 'operator answer' even though its value isn't printed.
     tryToWriteTypeOfExp(t, expr);
     storeExp(e, t, expr);
   }
 }
 else if (t->kind == ty_overloaded) {
   // If the exp is overloaded, but the act of writing makes it
   // unambiguous, add a suffix to the output to warn the user of this.
   exp *suffix=new nameExp(pos,
                           symbol::trans("overloadedMessage"));
   exp *callWithSuffix=new callExp(pos,
                                   callee, expr, suffix);

   if (callWithSuffix->getType(e)->kind != ty_error)
     baseExpTrans(e, callWithSuffix);
   else
     baseExpTrans(e, call);
 }
 else {
   // Interactive writing can proceed normally.
   storeAndWriteExp(e, t, expr);
 }
}

void expStm::interactiveTrans(coenv &e)
{
 // First check if it is the kind of expression that should be written.
 if (body->writtenToPrompt() &&
     settings::getSetting<bool>("interactiveWrite"))
   tryToWriteExp(e, body);
 else
   baseExpTrans(e, body);
}



void ifStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"ifStm",indent, getPos());

 test->prettyprint(out, indent+1);
 onTrue->prettyprint(out, indent+1);
 if (onFalse)
   onFalse->prettyprint(out, indent+1);
}

void ifStm::trans(coenv &e)
{
 label elseLabel = e.c.fwdLabel();
 label end = e.c.fwdLabel();

 test->transConditionalJump(e, false, elseLabel);

 onTrue->markTrans(e);

 if (onFalse) {
   // Encode the jump around the 'else' clause at the end of the 'if' clause
   e.c.useLabel(inst::jmp,end);

   e.c.defLabel(elseLabel);
   onFalse->markTrans(e);
 } else {
   e.c.defLabel(elseLabel);
 }


 e.c.defLabel(end);
}



void transLoopBody(coenv &e, stm *body) {
 // The semantics of the language are defined so that any variable declared
 // inside a loop are new variables for each iteration of the loop.  For
 // instance, the code
 //
 //     int f();
 //     for (int i = 0; i < 10; ++i) {
 //       int j=10*i;
 //       if (i == 5)
 //         f = new int() { return j; };
 //     }
 //     write(f());
 //
 // will write 50.  This is implemented by allocating a new frame for each
 // iteration.  However, this can have a big performance hit, so we first
 // translate the code without the frame, check if it needed the closure, and
 // rewrite the code if necessary.

 label start = e.c.defNewLabel();

 // Encode a no-op, in case we need to jump over the default implementation
 // to a special case.
 e.c.encode(inst::nop);

 body->markTrans(e);

 // Don't re-translate if there were errors.
 if (em.errors())
   return;

 if (e.c.usesClosureSinceLabel(start)){
   // Jump over the old section.
   label end = e.c.defNewLabel();
   e.c.encodePatch(start, end);

   // Let coder know that break and continue need to pop the frame.
   e.c.loopPushesFrame();

   e.c.encodePushFrame();
   body->markTrans(e);
   e.c.encodePopFrame();
 }
}

void whileStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"whileStm",indent, getPos());

 test->prettyprint(out, indent+1);
 body->prettyprint(out, indent+1);
}

void whileStm::trans(coenv &e)
{
 label end = e.c.fwdLabel();
 label start = e.c.defNewLabel();
 e.c.pushLoop(start, end);

 test->transConditionalJump(e, false, end);

 transLoopBody(e,body);

 e.c.useLabel(inst::jmp,start);
 e.c.defLabel(end);

 e.c.popLoop();
}



 void doStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"doStm",indent, getPos());

 body->prettyprint(out, indent+1);
 test->prettyprint(out, indent+1);
}

void doStm::trans(coenv &e)
{
 label testLabel = e.c.fwdLabel();
 label end = e.c.fwdLabel();
 e.c.pushLoop(testLabel, end);

 label start = e.c.defNewLabel();

 transLoopBody(e,body);

 e.c.defLabel(testLabel);

 test->transConditionalJump(e, true, start);

 e.c.defLabel(end);

 e.c.popLoop();
}

void forStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"forStm",indent, getPos());

 if (init) init->prettyprint(out, indent+1);
 if (test) test->prettyprint(out, indent+1);
 if (update) update->prettyprint(out, indent+1);
 body->prettyprint(out, indent+1);
}

void forStm::trans(coenv &e)
{
 // Any vardec in the initializer needs its own scope.
 e.e.beginScope();
 if (init)
   init->markTrans(e);

 label ctarget = e.c.fwdLabel();
 label end = e.c.fwdLabel();
 e.c.pushLoop(ctarget, end);

 label start = e.c.defNewLabel();
 if(test) {
   test->transConditionalJump(e, false, end);
 }

 transLoopBody(e,body);

 e.c.defLabel(ctarget);

 if (update)
   update->markTrans(e);
 e.c.useLabel(inst::jmp,start);

 e.c.defLabel(end);

 e.c.popLoop();

 e.e.endScope();
}



void extendedForStm::prettyprint(ostream &out, Int indent)
{
 prettyindent(out, indent);
 out << "extendedForStm: '" << var << "'\n";

 start->prettyprint(out, indent+1);
 set->prettyprint(out, indent+1);
 body->prettyprint(out, indent+1);
}

void extendedForStm::trans(coenv &e) {
 // Translate into the syntax:
 //
 // start[] a = set;
 // for (int i=0; i < a.length; ++i) {
 //   start var=a[i];
 //   body
 // }

 position pos=getPos();

 // Use gensyms for the variable names so as not to pollute the namespace.
 symbol a=symbol::gensym("a");
 symbol i=symbol::gensym("i");

 // Get the start type.  Handle type inference as a special case.
 types::ty *t = start->trans(e, true);
 if (t->kind == types::ty_inferred) {

   // First ensure the array expression is an unambiguous array.
   types::ty *at = set->cgetType(e);
   if (at->kind != ty_array) {
     em.error(set->getPos());
     em << "expression is not an array of inferable type";

     // On failure, don't bother trying to translate the loop.
     return;
   }

   // var a=set;
   tyEntryTy tet(pos, primInferred());
   decid dec1(pos, new decidstart(pos, a), set);
   vardec(pos, &tet, &dec1).trans(e);
 }
 else {
   // start[] a=set;
   arrayTy at(pos, start, new dimensions(pos));
   decid dec1(pos, new decidstart(pos, a), set);
   vardec(pos, &at, &dec1).trans(e);
 }

 // { start var=a[i]; body }
 block b(pos);
 decid dec2(pos,
            new decidstart(pos, var),
            new subscriptExp(pos, new nameExp(pos, a),
                             new nameExp(pos, i)));
 b.add(new vardec(pos, start, &dec2));
 b.add(body);

 // for (int i=0; i < a.length; ++i)
 //   <block>
 forStm(pos,
        new vardec(pos, new tyEntryTy(pos, primInt()),
                   new decid(pos,
                             new decidstart(pos, i),
                             new intExp(pos, 0))),
        new binaryExp(pos,
                      new nameExp(pos, i),
                      SYM_LT,
                      new nameExp(pos,
                                  new qualifiedName(pos,
                                                    new simpleName(pos, a),
                                                    symbol::trans("length")))),
        new expStm(pos, new prefixExp(pos, new nameExp(pos, i), SYM_PLUS)),
        new blockStm(pos, &b)).trans(e);
}




void breakStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"breakStm",indent, getPos());
}

void breakStm::trans(coenv &e)
{
 if (!e.c.encodeBreak()) {
   em.error(getPos());
   em << "break statement outside of a loop";
 }
}


void continueStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out,"continueStm",indent, getPos());
}

void continueStm::trans(coenv &e)
{
 if (!e.c.encodeContinue()) {
   em.error(getPos());
   em << "continue statement outside of a loop";
 }
}


void returnStm::prettyprint(ostream &out, Int indent)
{
 prettyname(out, "returnStm",indent, getPos());

 if (value)
   value->prettyprint(out, indent+1);
}

void returnStm::trans(coenv &e)
{
 types::ty *t = e.c.getReturnType();

 if (t->kind == ty_void) {
   if (value) {
     em.error(getPos());
     em << "function cannot return a value";
   }
   if (e.c.isRecord())
     e.c.encode(inst::pushclosure);
 }
 else {
   if (value) {
     value->transToType(e, t);
   }
   else {
     em.error(getPos());
     em << "function must return a value";
   }
 }

 // NOTE: Currently, a return statement in a module definition will end
 // the initializer.  Should this be allowed?
 e.c.encode(inst::ret);
}



void stmExpList::prettyprint(ostream &out, Int indent)
{
 prettyname(out, "stmExpList",indent, getPos());

 for (mem::list<stm *>::iterator p = stms.begin(); p != stms.end(); ++p)
   (*p)->prettyprint(out, indent+1);
}

void stmExpList::trans(coenv &e)
{
 for (mem::list<stm *>::iterator p = stms.begin(); p != stms.end(); ++p)
   (*p)->markTrans(e);
}


} // namespace absyntax

You are viewing proxied material from ftp.icm.edu.pl. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.