/*-----------------------------------------------------------------*/
static void
computeDFOrdering (eBBlock * ebbp, int *count)
{
ebbp->visited = 1;
/* for each successor that is not visited */
applyToSet (ebbp->succList, DFOrdering, count);
/* set the depth first number */
ebbp->dfnum = *count;
*count -= 1;
}
/*-----------------------------------------------------------------*/
void
computeDataFlow (eBBlock ** ebbs, int count)
{
int i;
int change = 1;
while (change)
{
change = 0;
/* for all blocks */
for (i = 0; i < count; i++)
{
set *pred;
set *oldOut;
int firstTime;
eBBlock *pBlock;
/* if this is the entry block then continue */
/* since entry block can never have any inExprs */
if (ebbs[i]->noPath)
continue;
/* get blocks that can come to this block */
pred = edgesTo (ebbs[i]);
/* make a copy of the outExpressions : to be */
/* used for iteration */
oldOut = setFromSet (ebbs[i]->outExprs);
setToNull ((void **) &ebbs[i]->inDefs);
/* indefitions are easy just merge them by union */
/* these are the definitions that can possibly */
/* reach this block */
firstTime = 1;
applyToSet (pred, mergeInDefs, ebbs[i], &firstTime);
/* if none of the edges coming to this block */
/* dominate this block then add the immediate dominator */
/* of this block to the list of predecessors */
for (pBlock = setFirstItem (pred); pBlock;
pBlock = setNextItem (pred))
{
if (bitVectBitValue (ebbs[i]->domVect, pBlock->bbnum))
break;
}
/* get the immediate dominator and put it there */
if (!pBlock)
{
eBBlock *idom = immedDom (ebbs, ebbs[i]);
if (idom)
addSetHead (&pred, idom);
}
/* figure out the incoming expressions */
/* this is a little more complex */
setToNull ((void **) &ebbs[i]->inExprs);
if (optimize.global_cse)
{
firstTime = 1;
applyToSet (pred, mergeInExprs, ebbs[i], &firstTime);
}
setToNull ((void **) &pred);
/* do cse with computeOnly flag set to TRUE */
/* this by far the quickest way of computing */
cseBBlock (ebbs[i], TRUE, ebbs, count);
/* if it change we will need to iterate */
change += !isSetsEqualWith (ebbs[i]->outExprs, oldOut, isCseDefEqual);
}
if (!change) /* iterate till no change */
break;
}
return;
}
/*-----------------------------------------------------------------*/
int
killDeadCode (eBBlock ** ebbs, int count)
{
int change = 1;
int gchange = 0;
int i = 0;
/* basic algorithm :- */
/* first the exclusion rules :- */
/* 1. if result is a global or volatile then skip */
/* 2. if assignment and result is a temp & isaddr then skip */
/* since this means array & pointer access, will be taken */
/* care of by alias analysis. */
/* 3. if the result is used in the remainder of the block skip */
/* 4. if this definition does not reach the end of the block */
/* i.e. the result is not present in the outExprs then KILL */
/* 5. if it reaches the end of block & is used by some success */
/* or then skip */
/* else KILL */
/* this whole process is carried on iteratively till no change */
while (1)
{
change = 0;
/* for all blocks do */
for (i = 0; i < count; i++)
{
iCode *ic;
/* for all instructions in the block do */
for (ic = ebbs[i]->sch; ic; ic = ic->next)
{
int kill, j;
kill = 0;
if (SKIP_IC (ic) ||
ic->op == IFX ||
ic->op == RETURN)
continue;
/* if the result is volatile then continue */
if (IC_RESULT (ic) && isOperandVolatile (IC_RESULT (ic), FALSE))
continue;
/* if the result is a temp & isaddr then skip */
if (IC_RESULT (ic) && POINTER_SET (ic))
continue;
/* if the result is used in the remainder of the */
/* block then skip */
if (usedInRemaining (IC_RESULT (ic), ic->next))
continue;
/* does this definition reach the end of the block
or the usage is zero then we can kill */
if (!bitVectBitValue (ebbs[i]->outDefs, ic->key))
kill = 1; /* if not we can kill it */
else
{
/* if this is a global variable or function parameter */
/* we cannot kill anyway */
if (isOperandGlobal (IC_RESULT (ic)) ||
(OP_SYMBOL (IC_RESULT (ic))->_isparm &&
!OP_SYMBOL (IC_RESULT (ic))->ismyparm))
continue;
/* if we are sure there are no usages */
if (bitVectIsZero (OP_USES (IC_RESULT (ic))))
{
kill = 1;
goto kill;
}
/* reset visited flag */
for (j = 0; j < count; ebbs[j++]->visited = 0);
/* find out if this definition is alive */
if (applyToSet (ebbs[i]->succList,
isDefAlive,
ic))
continue;
kill = 1;
}
kill:
/* kill this one if required */
if (kill)
{
change = 1;
gchange++;
/* eliminate this */
remiCodeFromeBBlock (ebbs[i], ic);
/* now delete from defUseSet */
deleteItemIf (&ebbs[i]->outExprs, ifDiCodeIsX, ic);
bitVectUnSetBit (ebbs[i]->outDefs, ic->key);
/* and defset of the block */
bitVectUnSetBit (ebbs[i]->defSet, ic->key);
/* for the left & right remove the usage */
if (IS_SYMOP (IC_LEFT (ic)))
bitVectUnSetBit (OP_USES (IC_LEFT (ic)), ic->key);
if (IS_SYMOP (IC_RIGHT (ic)))
bitVectUnSetBit (OP_USES (IC_RIGHT (ic)), ic->key);
}
} /* end of all instructions */
if (!ebbs[i]->sch && !ebbs[i]->noPath)
disconBBlock (ebbs[i], ebbs, count);
} /* end of for all blocks */
if (!change)
break;
} /* end of while(1) */
return gchange;
}
/*-----------------------------------------------------------------*/
static symbol *
createStackSpil (symbol * sym)
{
symbol *sloc = NULL;
struct dbuf_s dbuf;
D (D_ALLOC, ("createStackSpil: for sym %p %s\n", sym, sym->name));
/* first go try and find a free one that is already
existing on the stack */
if (applyToSet (_G.stackSpil, isFreeSTM8, &sloc, sym))
{
/* found a free one : just update & return */
sym->usl.spillLoc = sloc;
sym->stackSpil = 1;
sloc->isFree = 0;
addSetHead (&sloc->usl.itmpStack, sym);
D (D_ALLOC, ("createStackSpil: found existing\n"));
return sym;
}
/* could not then have to create one , this is the hard part
we need to allocate this on the stack : this is really a
hack!! but cannot think of anything better at this time */
dbuf_init (&dbuf, 128);
dbuf_printf (&dbuf, "sloc%d", _G.slocNum++);
sloc = newiTemp (dbuf_c_str (&dbuf));
dbuf_destroy (&dbuf);
/* set the type to the spilling symbol */
sloc->type = copyLinkChain (sym->type);
sloc->etype = getSpec (sloc->type);
SPEC_SCLS (sloc->etype) = S_AUTO;
SPEC_EXTR (sloc->etype) = 0;
SPEC_STAT (sloc->etype) = 0;
SPEC_VOLATILE (sloc->etype) = 0;
allocLocal (sloc);
sloc->isref = 1; /* to prevent compiler warning */
wassertl (currFunc, "Local variable used outside of function.");
/* if it is on the stack then update the stack */
if (IN_STACK (sloc->etype))
{
if (currFunc)
currFunc->stack += getSize (sloc->type);
_G.stackExtend += getSize (sloc->type);
}
else
{
_G.dataExtend += getSize (sloc->type);
}
/* add it to the stackSpil set */
addSetHead (&_G.stackSpil, sloc);
sym->usl.spillLoc = sloc;
sym->stackSpil = 1;
/* add it to the set of itempStack set
of the spill location */
addSetHead (&sloc->usl.itmpStack, sym);
D (D_ALLOC, ("createStackSpil: created new\n"));
return sym;
}
