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(NFC) Clean up dead code in FlowGraph.cpp
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Remove dead functions as well as unused arguments. Also remove code in CFG
construction that deal with break/while/cont/halt as vISA no longer supports
structured CF opcode. They may still be produced internally by the structurizer
on legacy platforms so we can't remove them entirely. This also does not apply
to if/endif which may still be generated by math macros; future work is to
replace them with goto/join.
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@Wei-Chen-Intel @igcbot
Wei-Chen-Intel authored and igcbot committed Aug 22, 2023
1 parent 0c3c95d commit 7751fb3
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Showing 2 changed files with 14 additions and 120 deletions.
125 changes: 12 additions & 113 deletions visa/FlowGraph.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -743,57 +743,20 @@ void FlowGraph::constructFlowGraph(INST_LIST &instlist) {
addUniquePredSuccEdges(curr_BB, next_BB);
}
} // if (i->opcode()
else if (i->opcode() == G4_if || i->opcode() == G4_while ||
i->opcode() == G4_else) {
else if (i->opcode() == G4_if) {
hasSIMDCF = true;
if (i->asCFInst()->getJip()->isLabel()) {
if (i->opcode() == G4_else || i->opcode() == G4_while) {
// for G4_while, jump no matter predicate
if (i->getPredicate()) {
addPredSuccEdges(curr_BB,
getLabelBB(labelMap, i->asCFInst()->getJip()));
} else if ((i->getPredicate() != NULL) ||
((i->getCondMod() != NULL) && (i->getSrc(0) != NULL) &&
(i->getSrc(1) != NULL))) {
addPredSuccEdges(curr_BB,
getLabelBB(labelMap, i->asCFInst()->getJip()));
}
}
if (i->opcode() == G4_while) {
// always do this since break jumps to while, otherwise code after
// while without predicate appears unreachable. add fall through
// edge if while is not the last instruction
if (next_BB) {
addPredSuccEdges(curr_BB, next_BB);
}
} else {
// always fall through
addPredSuccEdges(curr_BB, next_BB); // add fall through edge
}
} else if (i->opcode() == G4_break || i->opcode() == G4_cont ||
i->opcode() == G4_halt) {
// JIP and UIP must have been computed at this point
vISA_ASSERT(i->asCFInst()->getJip() != NULL &&
i->asCFInst()->getUip() != NULL,
"null JIP or UIP for break/cont instruction");
addPredSuccEdges(curr_BB,
getLabelBB(labelMap, i->asCFInst()->getJip()));

if (strcmp(i->asCFInst()->getJipLabelStr(),
i->asCFInst()->getUipLabelStr()) != 0)
addPredSuccEdges(curr_BB,
getLabelBB(labelMap, i->asCFInst()->getUip()));

//
// pred means conditional branch
//
if (i->getPredicate() != NULL) {
// add fall through edge
addPredSuccEdges(curr_BB, next_BB);
}
// always fall through
addPredSuccEdges(curr_BB, next_BB);
} else if (i->isReturn() || i->opcode() == G4_pseudo_exit) {
// does nothing for unconditional return;
// later phase will link the return and the return address
if (i->getPredicate() != NULL) {
if (i->getPredicate()) {
// add fall through edge
addPredSuccEdges(curr_BB, next_BB);
}
Expand Down Expand Up @@ -901,7 +864,7 @@ void FlowGraph::constructFlowGraph(INST_LIST &instlist) {
removeRedundantLabels();
pKernel->dumpToFile("after.PostStructurizerRedundantLabels");
} else {
processGoto(hasSIMDCF);
processGoto();
pKernel->dumpToFile("after.ProcessGoto");
}
}
Expand All @@ -912,9 +875,12 @@ void FlowGraph::constructFlowGraph(INST_LIST &instlist) {
reassignBlockIDs();
findBackEdges();

// TODO: I think this can be removed since vISA no longer has structured CF.
// For math intrinsics if/endif may still be generated, but they are present
// for IGC as well, which suggests this pass is not needed.
if (hasSIMDCF &&
pKernel->getInt32KernelAttr(Attributes::ATTR_Target) == VISA_CM) {
processSCF(funcInfoHashTable);
processSCF();
addSIMDEdges();
}

Expand Down Expand Up @@ -2144,51 +2110,6 @@ void FlowGraph::mergeFReturns() {
}
}

//
// Add a dummy BB for multiple-exit flow graph
// The criteria of a valid multiple-exit flow graph is:
// (1). equal or less than one BB w/o successor has non-EOT last instruction;
// (2). Other BBs w/o successor must end with EOT
//
void FlowGraph::linkDummyBB() {
//
// check the flow graph to find if it satify the criteria and record the exit
// BB
//
std::list<G4_BB *> exitBBs;
int nonEotExitBB = 0;
for (G4_BB *bb : BBs) {
if (bb->Succs.empty()) {
exitBBs.push_back(bb); // record exit BBs
G4_INST *last = bb->back();
if (last == NULL) {
vISA_ASSERT(false, "ERROR: Invalid flow graph with empty exit BB!");
}
if (!bb->isLastInstEOT()) {
nonEotExitBB++;
if (nonEotExitBB > 1) {
vISA_ASSERT(false, "ERROR: Invalid flow graph with more than one "
"exit BB not end with EOT!");
}
}
}
}

//
// create the dummy BB and link the exit BBs to it
//
if (nonEotExitBB == 1 && exitBBs.size() > 1) {
G4_BB *dumBB = createNewBB();
dumBB->markEmpty(builder, "DUMMY_LAST_BB");
BBs.push_back(dumBB);

for (G4_BB *bb : exitBBs) {
dumBB->Preds.push_back(bb);
bb->Succs.push_back(dumBB);
}
}
}

//
// Re-assign block ID so that we can use id to determine the ordering of two
// blocks in the code layout
Expand Down Expand Up @@ -2271,7 +2192,7 @@ struct StructuredCF {
* The simd control flow blocks must be well-structured
*
*/
void FlowGraph::processSCF(FuncInfoHashTable &FuncInfoMap) {
void FlowGraph::processSCF() {
std::stack<StructuredCF *> ifAndLoops;
std::vector<StructuredCF *> structuredSimdCF;

Expand Down Expand Up @@ -2853,28 +2774,6 @@ void FlowGraph::setPhysicalPredSucc() {
}
}

G4_Label *FlowGraph::insertEndif(G4_BB *bb, G4_ExecSize execSize,
bool createLabel) {
// endif is placed immediately after the label
G4_INST *endifInst = builder->createInternalCFInst(NULL, G4_endif, execSize,
NULL, NULL, InstOpt_NoOpt);
INST_LIST_ITER iter = bb->begin();
vISA_ASSERT(iter != bb->end(), "empty BB");
iter++;
bb->insertBefore(iter, endifInst);

// this block may be a target of multiple ifs, in which case we will need to
// insert one endif for each if. The innermost endif will use the BB label,
// while for the other endifs a new label will be created for each of them.
if (createLabel) {
G4_Label *label = builder->createLocalBlockLabel();
endifWithLabels.emplace(endifInst, label);
return label;
} else {
return bb->getLabel();
}
}

// This function set the JIP of the endif to the target instruction (either
// endif or while)
void FlowGraph::setJIPForEndif(G4_INST *endif, G4_INST *target,
Expand Down Expand Up @@ -2948,7 +2847,7 @@ void FlowGraph::convertGotoToJmpi(G4_INST *gotoInst) {
* well-formed vISA program should not have overlapped goto and structured CF
* instructions.
*/
void FlowGraph::processGoto(bool HasSIMDCF) {
void FlowGraph::processGoto() {
// For a given loop (StartBB, EndBB) (EndBB->StartBB is a backedge), this
// function return a BB in which an out-of-loop join will be inserted.
//
Expand Down
9 changes: 2 additions & 7 deletions visa/FlowGraph.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -395,8 +395,8 @@ class FlowGraph {
void mergeReturn(FuncInfoHashTable &funcInfoTable);
G4_BB *mergeSubRoutineReturn(G4_Label *subroutine);
void normalizeSubRoutineBB(FuncInfoHashTable &funcInfoTable);
void processGoto(bool HasSIMDCF);
void processSCF(FuncInfoHashTable &FuncInfoMap);
void processGoto();
void processSCF();
// Insert a join at the beginning of 'bb' with given 'execsize' and
// 'maskoffset'. If a join is already present, update that join to cover the
// given 'execsize' and 'maskoffset'.
Expand All @@ -405,7 +405,6 @@ class FlowGraph {

// functions for structure analysis
G4_Kernel *getKernel() const { return pKernel; }
G4_Label *insertEndif(G4_BB *bb, G4_ExecSize execSize, bool createLabel);
void setJIPForEndif(G4_INST *endif, G4_INST *target, G4_BB *targetBB);
void convertGotoToJmpi(G4_INST *gotoInst);
G4_BB *getSinglePredecessor(G4_BB *BB, G4_BB *ExcludedPred) const;
Expand Down Expand Up @@ -490,10 +489,6 @@ class FlowGraph {
//
void removeEmptyBlocks();
//
// Add a dummy BB for multiple-exit flow graph
//
void linkDummyBB();
//
// Re-assign block ID so that we can use id to determine the ordering of two
// blocks in the code layout
//
Expand Down

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