/*
* Copyright 2011 Christoph Bumiller
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include "nv50_ir.h"
#include "nv50_ir_target.h"
namespace nv50_ir {
// Converts nv50 IR generated from TGSI to SSA form.
// DominatorTree implements an algorithm for finding immediate dominators,
// as described by T. Lengauer & R. Tarjan.
class DominatorTree : public Graph
{
public:
DominatorTree(Graph *cfg);
~DominatorTree() { }
bool dominates(BasicBlock *, BasicBlock *);
void findDominanceFrontiers();
private:
void build();
void buildDFS(Node *);
void squash(int);
inline void link(int, int);
inline int eval(int);
void debugPrint();
Graph *cfg;
Node **vert;
int *data;
const int count;
#define SEMI(i) (data[(i) + 0 * count])
#define ANCESTOR(i) (data[(i) + 1 * count])
#define PARENT(i) (data[(i) + 2 * count])
#define LABEL(i) (data[(i) + 3 * count])
#define DOM(i) (data[(i) + 4 * count])
};
void DominatorTree::debugPrint()
{
for (int i = 0; i < count; ++i) {
INFO("SEMI(%i) = %i\n", i, SEMI(i));
INFO("ANCESTOR(%i) = %i\n", i, ANCESTOR(i));
INFO("PARENT(%i) = %i\n", i, PARENT(i));
INFO("LABEL(%i) = %i\n", i, LABEL(i));
INFO("DOM(%i) = %i\n", i, DOM(i));
}
}
DominatorTree::DominatorTree(Graph *cfgraph) : cfg(cfgraph),
count(cfg->getSize())
{
int i = 0;
vert = new Node * [count];
data = new int[5 * count];
for (IteratorRef it = cfg->iteratorDFS(true); !it->end(); it->next(), ++i) {
vert[i] = reinterpret_cast<Node *>(it->get());
vert[i]->tag = i;
LABEL(i) = i;
SEMI(i) = ANCESTOR(i) = -1;
}
build();
delete[] vert;
delete[] data;
}
void DominatorTree::buildDFS(Graph::Node *node)
{
SEMI(node->tag) = node->tag;
for (Graph::EdgeIterator ei = node->outgoing(); !ei.end(); ei.next()) {
if (SEMI(ei.getNode()->tag) < 0) {
buildDFS(ei.getNode());
PARENT(ei.getNode()->tag) = node->tag;
}
}
}
void DominatorTree::squash(int v)
{
if (ANCESTOR(ANCESTOR(v)) >= 0) {
squash(ANCESTOR(v));
if (SEMI(LABEL(ANCESTOR(v))) < SEMI(LABEL(v)))
LABEL(v) = LABEL(ANCESTOR(v));
ANCESTOR(v) = ANCESTOR(ANCESTOR(v));
}
}
int DominatorTree::eval(int v)
{
if (ANCESTOR(v) < 0)
return v;
squash(v);
return LABEL(v);
}
void DominatorTree::link(int v, int w)
{
ANCESTOR(w) = v;
}
void DominatorTree::build()
{
DLList *bucket = new DLList[count];
Node *nv, *nw;
int p, u, v, w;
buildDFS(cfg->getRoot());
for (w = count - 1; w >= 1; --w) {
nw = vert[w];
assert(nw->tag == w);
for (Graph::EdgeIterator ei = nw->incident(); !ei.end(); ei.next()) {
nv = ei.getNode();
v = nv->tag;
u = eval(v);
if (SEMI(u) < SEMI(w))
SEMI(w) = SEMI(u);
}
p = PARENT(w);
bucket[SEMI(w)].insert(nw);
link(p, w);
for (DLList::Iterator it = bucket[p].iterator(); !it.end(); it.erase()) {
v = reinterpret_cast<Node *>(it.get())->tag;
u = eval(v);
DOM(v) = (SEMI(u) < SEMI(v)) ? u : p;
}
}
for (w = 1; w < count; ++w) {
if (DOM(w) != SEMI(w))
DOM(w) = DOM(DOM(w));
}
DOM(0) = 0;
insert(&BasicBlock::get(cfg->getRoot())->dom);
do {
p = 0;
for (v = 1; v < count; ++v) {
nw = &BasicBlock::get(vert[DOM(v)])->dom;;
nv = &BasicBlock::get(vert[v])->dom;
if (nw->getGraph() && !nv->getGraph()) {
++p;
nw->attach(nv, Graph::Edge::TREE);
}
}
} while (p);
delete[] bucket;
}
#undef SEMI
#undef ANCESTOR
#undef PARENT
#undef LABEL
#undef DOM
void DominatorTree::findDominanceFrontiers()
{
BasicBlock *bb;
for (IteratorRef dtIt = iteratorDFS(false); !dtIt->end(); dtIt->next()) {
EdgeIterator succIt, chldIt;
bb = BasicBlock::get(reinterpret_cast<Node *>(dtIt->get()));
bb->getDF().clear();
for (succIt = bb->cfg.outgoing(); !succIt.end(); succIt.next()) {
BasicBlock *dfLocal = BasicBlock::get(succIt.getNode());
if (dfLocal->idom() != bb)
bb->getDF().insert(dfLocal);
}
for (chldIt = bb->dom.outgoing(); !chldIt.end(); chldIt.next()) {
BasicBlock *cb = BasicBlock::get(chldIt.getNode());
DLList::Iterator dfIt = cb->getDF().iterator();
for (; !dfIt.end(); dfIt.next()) {
BasicBlock *dfUp = BasicBlock::get(dfIt);
if (dfUp->idom() != bb)
bb->getDF().insert(dfUp);
}
}
}
}
// liveIn(bb) = usedBeforeAssigned(bb) U (liveOut(bb) - assigned(bb))
void
Function::buildLiveSetsPreSSA(BasicBlock *bb, const int seq)
{
Function *f = bb->getFunction();
BitSet usedBeforeAssigned(allLValues.getSize(), true);
BitSet assigned(allLValues.getSize(), true);
bb->liveSet.allocate(allLValues.getSize(), false);
int n = 0;
for (Graph::EdgeIterator ei = bb->cfg.outgoing(); !ei.end(); ei.next()) {
BasicBlock *out = BasicBlock::get(ei.getNode());
if (out == bb)
continue;
if (out->cfg.visit(seq))
buildLiveSetsPreSSA(out, seq);
if (!n++)
bb->liveSet = out->liveSet;
else
bb->liveSet |= out->liveSet;
}
if (!n && !bb->liveSet.marker)
bb->liveSet.fill(0);
bb->liveSet.marker = true;
for (Instruction *i = bb->getEntry(); i; i = i->next) {
for (int s = 0; i->srcExists(s); ++s)
if (i->getSrc(s)->asLValue() && !assigned.test(i->getSrc(s)->id))
usedBeforeAssigned.set(i->getSrc(s)->id);
for (int d = 0; i->defExists(d); ++d)
assigned.set(i->getDef(d)->id);
}
if (bb == BasicBlock::get(f->cfgExit)) {
for (std::deque<ValueRef>::iterator it = f->outs.begin();
it != f->outs.end(); ++it) {
if (!assigned.test(it->get()->id))
usedBeforeAssigned.set(it->get()->id);
}
}
bb->liveSet.andNot(assigned);
bb->liveSet |= usedBeforeAssigned;
}
void
Function::buildDefSetsPreSSA(BasicBlock *bb, const int seq)
{
bb->defSet.allocate(allLValues.getSize(), !bb->liveSet.marker);
bb->liveSet.marker = true;
for (Graph::EdgeIterator ei = bb->cfg.incident(); !ei.end(); ei.next()) {
BasicBlock *in = BasicBlock::get(ei.getNode());
if (in->cfg.visit(seq))
buildDefSetsPreSSA(in, seq);
bb->defSet |= in->defSet;
}
for (Instruction *i = bb->getEntry(); i; i = i->next) {
for (int d = 0; i->defExists(d); ++d)
bb->defSet.set(i->getDef(d)->id);
}
}
class RenamePass
{
public:
RenamePass(Function *);
~RenamePass();
bool run();
void search(BasicBlock *);
inline LValue *getStackTop(Value *);
LValue *mkUndefined(Value *);
private:
Stack *stack;
Function *func;
Program *prog;
};
bool
Program::convertToSSA()
{
for (ArrayList::Iterator fi = allFuncs.iterator(); !fi.end(); fi.next()) {
Function *fn = reinterpret_cast<Function *>(fi.get());
if (!fn->convertToSSA())
return false;
}
return true;
}
// XXX: add edge from entry to exit ?
// Efficiently Computing Static Single Assignment Form and
// the Control Dependence Graph,
// R. Cytron, J. Ferrante, B. K. Rosen, M. N. Wegman, F. K. Zadeck
bool
Function::convertToSSA()
{
// 0. calculate live in variables (for pruned SSA)
buildLiveSets();
// 1. create the dominator tree
domTree = new DominatorTree(&cfg);
reinterpret_cast<DominatorTree *>(domTree)->findDominanceFrontiers();
// 2. insert PHI functions
DLList workList;
LValue *lval;
BasicBlock *bb;
int var;
int iterCount = 0;
int *hasAlready = new int[allBBlocks.getSize() * 2];
int *work = &hasAlready[allBBlocks.getSize()];
memset(hasAlready, 0, allBBlocks.getSize() * 2 * sizeof(int));
// for each variable
for (var = 0; var < allLValues.getSize(); ++var) {
if (!allLValues.get(var))
continue;
lval = reinterpret_cast<Value *>(allLValues.get(var))->asLValue();
if (!lval || lval->defs.empty())
continue;
++iterCount;
// TODO: don't add phi functions for values that aren't used outside
// the BB they're defined in
// gather blocks with assignments to lval in workList
for (Value::DefIterator d = lval->defs.begin();
d != lval->defs.end(); ++d) {
bb = ((*d)->getInsn() ? (*d)->getInsn()->bb : NULL);
if (!bb)
continue; // instruction likely been removed but not XXX deleted
if (work[bb->getId()] == iterCount)
continue;
work[bb->getId()] = iterCount;
workList.insert(bb);
}
// for each block in workList, insert a phi for lval in the block's
// dominance frontier (if we haven't already done so)
for (DLList::Iterator wI = workList.iterator(); !wI.end(); wI.erase()) {
bb = BasicBlock::get(wI);
DLList::Iterator dfIter = bb->getDF().iterator();
for (; !dfIter.end(); dfIter.next()) {
Instruction *phi;
BasicBlock *dfBB = BasicBlock::get(dfIter);
if (hasAlready[dfBB->getId()] >= iterCount)
continue;
hasAlready[dfBB->getId()] = iterCount;
// pruned SSA: don't need a phi if the value is not live-in
if (!dfBB->liveSet.test(lval->id))
continue;
phi = new_Instruction(this, OP_PHI, typeOfSize(lval->reg.size));
dfBB->insertTail(phi);
phi->setDef(0, lval);
for (int s = 0; s < dfBB->cfg.incidentCount(); ++s)
phi->setSrc(s, lval);
if (work[dfBB->getId()] < iterCount) {
work[dfBB->getId()] = iterCount;
wI.insert(dfBB);
}
}
}
}
delete[] hasAlready;
RenamePass rename(this);
return rename.run();
}
RenamePass::RenamePass(Function *fn) : func(fn), prog(fn->getProgram())
{
stack = new Stack[func->allLValues.getSize()];
}
RenamePass::~RenamePass()
{
if (stack)
delete[] stack;
}
LValue *
RenamePass::getStackTop(Value *val)
{
if (!stack[val->id].getSize())
return 0;
return reinterpret_cast<LValue *>(stack[val->id].peek().u.p);
}
LValue *
RenamePass::mkUndefined(Value *val)
{
LValue *lval = val->asLValue();
assert(lval);
LValue *ud = new_LValue(func, lval);
Instruction *nop = new_Instruction(func, OP_NOP, typeOfSize(lval->reg.size));
nop->setDef(0, ud);
BasicBlock::get(func->cfg.getRoot())->insertHead(nop);
return ud;
}
bool RenamePass::run()
{
if (!stack)
return false;
search(BasicBlock::get(func->domTree->getRoot()));
return true;
}
// Go through BBs in dominance order, create new values for each definition,
// and replace all sources with their current new values.
//
// NOTE: The values generated for function inputs/outputs have no connection
// to their corresponding outputs/inputs in other functions. Only allocation
// of physical registers will establish this connection.
//
void RenamePass::search(BasicBlock *bb)
{
LValue *lval, *ssa;
int d, s;
const Target *targ = prog->getTarget();
// Put current definitions for function inputs values on the stack.
// They can be used before any redefinitions are pushed.
if (bb == BasicBlock::get(func->cfg.getRoot())) {
for (std::deque<ValueDef>::iterator it = func->ins.begin();
it != func->ins.end(); ++it) {
lval = it->get()->asLValue();
assert(lval);
ssa = new_LValue(func, targ->nativeFile(lval->reg.file));
ssa->reg.size = lval->reg.size;
ssa->reg.data.id = lval->reg.data.id;
it->setSSA(ssa);
stack[lval->id].push(ssa);
}
}
for (Instruction *stmt = bb->getFirst(); stmt; stmt = stmt->next) {
// PHI sources get definitions from the passes through the incident BBs,
// so skip them here.
if (stmt->op != OP_PHI) {
for (s = 0; stmt->srcExists(s); ++s) {
lval = stmt->getSrc(s)->asLValue();
if (!lval)
continue;
// Values on the stack created in previously visited blocks, and
// function inputs, will be valid because they dominate this one.
lval = getStackTop(lval);
if (!lval)
lval = mkUndefined(stmt->getSrc(s));
stmt->setSrc(s, lval);
}
}
for (d = 0; stmt->defExists(d); ++d) {
lval = stmt->def(d).get()->asLValue();
assert(lval);
stmt->def(d).setSSA(
new_LValue(func, targ->nativeFile(lval->reg.file)));
stmt->def(d).get()->reg.size = lval->reg.size;
stmt->def(d).get()->reg.data.id = lval->reg.data.id;
stack[lval->id].push(stmt->def(d).get());
}
}
// Update sources of PHI ops corresponding to this BB in outgoing BBs.
for (Graph::EdgeIterator ei = bb->cfg.outgoing(); !ei.end(); ei.next()) {
Instruction *phi;
int p = 0;
BasicBlock *sb = BasicBlock::get(ei.getNode());
// which predecessor of sb is bb ?
for (Graph::EdgeIterator ei = sb->cfg.incident(); !ei.end(); ei.next()) {
if (ei.getNode() == &bb->cfg)
break;
++p;
}
assert(p < sb->cfg.incidentCount());
for (phi = sb->getPhi(); phi && phi->op == OP_PHI; phi = phi->next) {
lval = getStackTop(phi->getSrc(p));
if (!lval)
lval = mkUndefined(phi->getSrc(p));
phi->setSrc(p, lval);
}
}
// Visit the BBs we dominate.
for (Graph::EdgeIterator ei = bb->dom.outgoing(); !ei.end(); ei.next())
search(BasicBlock::get(ei.getNode()));
// Update function outputs to the last definitions of their pre-SSA values.
// I hope they're unique, i.e. that we get PHIs for all of them ...
if (bb == BasicBlock::get(func->cfgExit)) {
for (std::deque<ValueRef>::iterator it = func->outs.begin();
it != func->outs.end(); ++it) {
lval = it->get()->asLValue();
if (!lval)
continue;
lval = getStackTop(lval);
if (!lval)
lval = mkUndefined(it->get());
it->set(lval);
}
}
// Pop the values we created in this block from the stack because we will
// return to blocks that we do not dominate.
for (Instruction *stmt = bb->getFirst(); stmt; stmt = stmt->next) {
if (stmt->op == OP_NOP)
continue;
for (d = 0; stmt->defExists(d); ++d)
stack[stmt->def(d).preSSA()->id].pop();
}
}
} // namespace nv50_ir