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refine code for picking target sites to avoid unecessary moves

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This commit is contained in:
Joel Dice 2009-04-26 12:19:16 -06:00
parent 64b529c915
commit f80fb9b536
1 changed files with 23 additions and 16 deletions
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39
src/compiler.cpp
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@ -1089,7 +1089,11 @@ FrameResource::thaw(Context* c, Value* v)
class Target {
public:
static const unsigned Penalty = 10;
static const unsigned MinimumRegisterCost = 0;
static const unsigned MinimumFrameCost = 1;
static const unsigned StealPenalty = 2;
static const unsigned StealUniquePenalty = 4;
static const unsigned LowRegisterPenalty = 10;
static const unsigned Impossible = 20;
Target(): cost(Impossible) { }
@ -1118,9 +1122,9 @@ resourceCost(Context* c UNUSED, Value* v, Resource* r)
if (v and buddies(r->value, v)) {
return 0;
} else if (hasMoreThanOneSite(r->value)) {
return 2;
return Target::StealPenalty;
} else {
return 4;
return Target::StealUniquePenalty;
}
} else {
return 0;
@ -1135,7 +1139,7 @@ pickRegisterTarget(Context* c, Value* v, uint32_t mask, unsigned* cost)
for (int i = c->arch->registerCount() - 1; i >= 0; --i) {
if ((1 << i) & mask) {
RegisterResource* r = c->registerResources + i;
unsigned myCost = resourceCost(c, v, r);
unsigned myCost = resourceCost(c, v, r) + Target::MinimumRegisterCost;
if ((static_cast<uint32_t>(1) << i) == mask) {
*cost = myCost;
return i;
@ -1161,7 +1165,8 @@ pickRegisterTarget(Context* c, Value* v, uint32_t mask)
unsigned
frameCost(Context* c, Value* v, int frameIndex)
{
return resourceCost(c, v, c->frameResources + frameIndex) + 1;
return resourceCost(c, v, c->frameResources + frameIndex)
+ Target::MinimumFrameCost;
}
Target
@ -1173,7 +1178,7 @@ pickFrameTarget(Context* c, Value* v)
do {
if (p->home >= 0) {
Target mine(p->home, MemoryOperand, frameCost(c, v, p->home));
if (mine.cost == 1) {
if (mine.cost == Target::MinimumFrameCost) {
return mine;
} else if (mine.cost < best.cost) {
best = mine;
@ -1193,7 +1198,7 @@ pickAnyFrameTarget(Context* c, Value* v)
unsigned count = totalFrameSize(c);
for (unsigned i = 0; i < count; ++i) {
Target mine(i, MemoryOperand, frameCost(c, v, i));
if (mine.cost == 1) {
if (mine.cost == Target::MinimumFrameCost) {
return mine;
} else if (mine.cost < best.cost) {
best = mine;
@ -1212,7 +1217,7 @@ pickTarget(Context* c, Value* value, const SiteMask& mask,
mine.cost += registerPenalty;
if (mine.cost == 0) {
if (mine.cost == Target::MinimumRegisterCost) {
return mine;
} else if (mine.cost < best.cost) {
best = mine;
@ -1222,7 +1227,7 @@ pickTarget(Context* c, Value* value, const SiteMask& mask,
if ((mask.typeMask & (1 << MemoryOperand)) && mask.frameIndex >= 0) {
Target mine(mask.frameIndex, MemoryOperand,
frameCost(c, value, mask.frameIndex));
if (mine.cost == 0) {
if (mine.cost == Target::MinimumFrameCost) {
return mine;
} else if (mine.cost < best.cost) {
best = mine;
@ -1237,7 +1242,7 @@ pickTarget(Context* c, Read* read, bool intersectRead,
unsigned registerReserveCount)
{
unsigned registerPenalty = (c->availableRegisterCount > registerReserveCount
? 0 : Target::Penalty);
? 0 : Target::LowRegisterPenalty);
SiteMask mask;
read->intersect(&mask);
@ -1250,8 +1255,8 @@ pickTarget(Context* c, Read* read, bool intersectRead,
if (r) {
SiteMask intersection = mask;
if (r->intersect(&intersection)) {
best = pickTarget(c, read->value, mask, registerPenalty, best);
if (best.cost == 0) {
best = pickTarget(c, read->value, intersection, registerPenalty, best);
if (best.cost <= Target::MinimumFrameCost) {
return best;
}
}
@ -1259,7 +1264,7 @@ pickTarget(Context* c, Read* read, bool intersectRead,
}
best = pickTarget(c, read->value, mask, registerPenalty, best);
if (best.cost == 0) {
if (best.cost <= Target::MinimumFrameCost) {
return best;
}
@ -1271,7 +1276,7 @@ pickTarget(Context* c, Read* read, bool intersectRead,
mine.cost += registerPenalty;
if (mine.cost == 0) {
if (mine.cost == Target::MinimumRegisterCost) {
return mine;
} else if (mine.cost < best.cost) {
best = mine;
@ -1279,14 +1284,16 @@ pickTarget(Context* c, Read* read, bool intersectRead,
}
{ Target mine = pickFrameTarget(c, read->value);
if (mine.cost == 0) {
if (mine.cost == Target::MinimumFrameCost) {
return mine;
} else if (mine.cost < best.cost) {
best = mine;
}
}
if (best.cost > 3 and c->availableRegisterCount == 0) {
if (best.cost >= Target::StealUniquePenalty
and c->availableRegisterCount == 0)
{
// there are no free registers left, so moving from memory to
// memory isn't an option - try harder to find an available frame
// site: