2 //---------------------------------------------------------------------------
7 // Convert SSA graph to instruction trees for instruction selection.
10 // The key goal is to group instructions into a single
11 // tree if one or more of them might be potentially combined into a single
12 // complex instruction in the target machine.
13 // Since this grouping is completely machine-independent, we do it as
14 // aggressive as possible to exploit any possible taret instructions.
15 // In particular, we group two instructions O and I if:
16 // (1) Instruction O computes an operand used by instruction I,
17 // and (2) O and I are part of the same basic block,
18 // and (3) O has only a single use, viz., I.
20 //---------------------------------------------------------------------------
22 #include "llvm/CodeGen/InstrForest.h"
23 #include "llvm/CodeGen/MachineCodeForInstruction.h"
24 #include "llvm/Function.h"
25 #include "llvm/iTerminators.h"
26 #include "llvm/iMemory.h"
27 #include "llvm/Constant.h"
28 #include "llvm/BasicBlock.h"
29 #include "llvm/CodeGen/MachineInstr.h"
30 #include "Support/STLExtras.h"
36 //------------------------------------------------------------------------
37 // class InstrTreeNode
38 //------------------------------------------------------------------------
41 InstrTreeNode::dump(int dumpChildren, int indent) const
48 LeftChild->dump(dumpChildren, indent+1);
50 RightChild->dump(dumpChildren, indent+1);
55 InstructionNode::InstructionNode(Instruction* I)
56 : InstrTreeNode(NTInstructionNode, I),
57 codeIsFoldedIntoParent(false)
59 opLabel = I->getOpcode();
61 // Distinguish special cases of some instructions such as Ret and Br
63 if (opLabel == Instruction::Ret && cast<ReturnInst>(I)->getReturnValue())
65 opLabel = RetValueOp; // ret(value) operation
67 else if (opLabel ==Instruction::Br && !cast<BranchInst>(I)->isUnconditional())
69 opLabel = BrCondOp; // br(cond) operation
71 else if (opLabel >= Instruction::SetEQ && opLabel <= Instruction::SetGT)
73 opLabel = SetCCOp; // common label for all SetCC ops
75 else if (opLabel == Instruction::Alloca && I->getNumOperands() > 0)
77 opLabel = AllocaN; // Alloca(ptr, N) operation
79 else if ((opLabel == Instruction::Load ||
80 opLabel == Instruction::GetElementPtr) &&
81 cast<MemAccessInst>(I)->hasIndices())
83 opLabel = opLabel + 100; // load/getElem with index vector
85 else if (opLabel == Instruction::And ||
86 opLabel == Instruction::Or ||
87 opLabel == Instruction::Xor ||
88 opLabel == Instruction::Not)
90 // Distinguish bitwise operators from logical operators!
91 if (I->getType() != Type::BoolTy)
92 opLabel = opLabel + 100; // bitwise operator
94 else if (opLabel == Instruction::Cast)
96 const Type *ITy = I->getType();
97 switch(ITy->getPrimitiveID())
99 case Type::BoolTyID: opLabel = ToBoolTy; break;
100 case Type::UByteTyID: opLabel = ToUByteTy; break;
101 case Type::SByteTyID: opLabel = ToSByteTy; break;
102 case Type::UShortTyID: opLabel = ToUShortTy; break;
103 case Type::ShortTyID: opLabel = ToShortTy; break;
104 case Type::UIntTyID: opLabel = ToUIntTy; break;
105 case Type::IntTyID: opLabel = ToIntTy; break;
106 case Type::ULongTyID: opLabel = ToULongTy; break;
107 case Type::LongTyID: opLabel = ToLongTy; break;
108 case Type::FloatTyID: opLabel = ToFloatTy; break;
109 case Type::DoubleTyID: opLabel = ToDoubleTy; break;
110 case Type::ArrayTyID: opLabel = ToArrayTy; break;
111 case Type::PointerTyID: opLabel = ToPointerTy; break;
113 // Just use `Cast' opcode otherwise. It's probably ignored.
121 InstructionNode::dumpNode(int indent) const
123 for (int i=0; i < indent; i++)
126 cerr << getInstruction()->getOpcodeName();
127 const MachineCodeForInstruction &mvec =
128 MachineCodeForInstruction::get(getInstruction());
131 cerr << "\tMachine Instructions: ";
133 for (unsigned int i=0; i < mvec.size(); ++i) {
135 if (i < mvec.size() - 1)
144 VRegListNode::dumpNode(int indent) const
146 for (int i=0; i < indent; i++)
149 cerr << "List" << "\n";
154 VRegNode::dumpNode(int indent) const
156 for (int i=0; i < indent; i++)
159 cerr << "VReg " << getValue() << "\t(type "
160 << (int) getValue()->getValueType() << ")" << "\n";
164 ConstantNode::dumpNode(int indent) const
166 for (int i=0; i < indent; i++)
169 cerr << "Constant " << getValue() << "\t(type "
170 << (int) getValue()->getValueType() << ")" << "\n";
174 LabelNode::dumpNode(int indent) const
176 for (int i=0; i < indent; i++)
179 cerr << "Label " << getValue() << "\n";
182 //------------------------------------------------------------------------
185 // A forest of instruction trees, usually for a single method.
186 //------------------------------------------------------------------------
188 InstrForest::InstrForest(Function *F)
190 for (Function::iterator FI = F->begin(), FE = F->end(); FI != FE; ++FI) {
191 BasicBlock *BB = *FI;
192 for_each(BB->begin(), BB->end(),
193 bind_obj(this, &InstrForest::buildTreeForInstruction));
197 InstrForest::~InstrForest()
199 for_each(treeRoots.begin(), treeRoots.end(), deleter<InstructionNode>);
203 InstrForest::dump() const
205 for (const_root_iterator I = roots_begin(); I != roots_end(); ++I)
206 (*I)->dump(/*dumpChildren*/ 1, /*indent*/ 0);
210 InstrForest::eraseRoot(InstructionNode* node)
212 for (RootSet::reverse_iterator RI=treeRoots.rbegin(), RE=treeRoots.rend();
215 treeRoots.erase(RI.base()-1);
219 InstrForest::noteTreeNodeForInstr(Instruction *instr,
220 InstructionNode *treeNode)
222 assert(treeNode->getNodeType() == InstrTreeNode::NTInstructionNode);
223 (*this)[instr] = treeNode;
224 treeRoots.push_back(treeNode); // mark node as root of a new tree
229 InstrForest::setLeftChild(InstrTreeNode *parent, InstrTreeNode *child)
231 parent->LeftChild = child;
232 child->Parent = parent;
233 if (child->getNodeType() == InstrTreeNode::NTInstructionNode)
234 eraseRoot((InstructionNode*) child); // no longer a tree root
238 InstrForest::setRightChild(InstrTreeNode *parent, InstrTreeNode *child)
240 parent->RightChild = child;
241 child->Parent = parent;
242 if (child->getNodeType() == InstrTreeNode::NTInstructionNode)
243 eraseRoot((InstructionNode*) child); // no longer a tree root
248 InstrForest::buildTreeForInstruction(Instruction *instr)
250 InstructionNode *treeNode = getTreeNodeForInstr(instr);
253 // treeNode has already been constructed for this instruction
254 assert(treeNode->getInstruction() == instr);
258 // Otherwise, create a new tree node for this instruction.
260 treeNode = new InstructionNode(instr);
261 noteTreeNodeForInstr(instr, treeNode);
263 if (instr->getOpcode() == Instruction::Call)
264 { // Operands of call instruction
268 // If the instruction has more than 2 instruction operands,
269 // then we need to create artificial list nodes to hold them.
270 // (Note that we only count operands that get tree nodes, and not
271 // others such as branch labels for a branch or switch instruction.)
273 // To do this efficiently, we'll walk all operands, build treeNodes
274 // for all appropriate operands and save them in an array. We then
275 // insert children at the end, creating list nodes where needed.
276 // As a performance optimization, allocate a child array only
277 // if a fixed array is too small.
280 InstrTreeNode **childArray =
281 (InstrTreeNode **)alloca(instr->getNumOperands()*sizeof(InstrTreeNode *));
284 // Walk the operands of the instruction
286 for (Instruction::op_iterator O = instr->op_begin(); O!=instr->op_end(); ++O)
290 // Check if the operand is a data value, not an branch label, type,
291 // method or module. If the operand is an address type (i.e., label
292 // or method) that is used in an non-branching operation, e.g., `add'.
293 // that should be considered a data value.
295 // Check latter condition here just to simplify the next IF.
296 bool includeAddressOperand =
297 (isa<BasicBlock>(operand) || isa<Function>(operand))
298 && !instr->isTerminator();
300 if (includeAddressOperand || isa<Instruction>(operand) ||
301 isa<Constant>(operand) || isa<Argument>(operand) ||
302 isa<GlobalVariable>(operand))
304 // This operand is a data value
306 // An instruction that computes the incoming value is added as a
307 // child of the current instruction if:
308 // the value has only a single use
309 // AND both instructions are in the same basic block.
310 // AND the current instruction is not a PHI (because the incoming
311 // value is conceptually in a predecessor block,
312 // even though it may be in the same static block)
314 // (Note that if the value has only a single use (viz., `instr'),
315 // the def of the value can be safely moved just before instr
316 // and therefore it is safe to combine these two instructions.)
318 // In all other cases, the virtual register holding the value
319 // is used directly, i.e., made a child of the instruction node.
321 InstrTreeNode* opTreeNode;
322 if (isa<Instruction>(operand) && operand->use_size() == 1 &&
323 cast<Instruction>(operand)->getParent() == instr->getParent() &&
324 instr->getOpcode() != Instruction::PHINode &&
325 instr->getOpcode() != Instruction::Call)
327 // Recursively create a treeNode for it.
328 opTreeNode = buildTreeForInstruction((Instruction*)operand);
330 else if (Constant *CPV = dyn_cast<Constant>(operand))
332 // Create a leaf node for a constant
333 opTreeNode = new ConstantNode(CPV);
337 // Create a leaf node for the virtual register
338 opTreeNode = new VRegNode(operand);
341 childArray[numChildren++] = opTreeNode;
345 //--------------------------------------------------------------------
346 // Add any selected operands as children in the tree.
347 // Certain instructions can have more than 2 in some instances (viz.,
348 // a CALL or a memory access -- LOAD, STORE, and GetElemPtr -- to an
349 // array or struct). Make the operands of every such instruction into
350 // a right-leaning binary tree with the operand nodes at the leaves
351 // and VRegList nodes as internal nodes.
352 //--------------------------------------------------------------------
354 InstrTreeNode *parent = treeNode;
358 unsigned instrOpcode = treeNode->getInstruction()->getOpcode();
359 assert(instrOpcode == Instruction::PHINode ||
360 instrOpcode == Instruction::Call ||
361 instrOpcode == Instruction::Load ||
362 instrOpcode == Instruction::Store ||
363 instrOpcode == Instruction::GetElementPtr);
366 // Insert the first child as a direct child
367 if (numChildren >= 1)
368 setLeftChild(parent, childArray[0]);
372 // Create a list node for children 2 .. N-1, if any
373 for (n = numChildren-1; n >= 2; n--)
375 // We have more than two children
376 InstrTreeNode *listNode = new VRegListNode();
377 setRightChild(parent, listNode);
378 setLeftChild(listNode, childArray[numChildren - n]);
382 // Now insert the last remaining child (if any).
383 if (numChildren >= 2)
386 setRightChild(parent, childArray[numChildren - 1]);