1 //===-- InstrForest.cpp - Build instruction forest for inst selection -----===//
3 // The key goal is to group instructions into a single
4 // tree if one or more of them might be potentially combined into a single
5 // complex instruction in the target machine.
6 // Since this grouping is completely machine-independent, we do it as
7 // aggressive as possible to exploit any possible taret instructions.
8 // In particular, we group two instructions O and I if:
9 // (1) Instruction O computes an operand used by instruction I,
10 // and (2) O and I are part of the same basic block,
11 // and (3) O has only a single use, viz., I.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/CodeGen/InstrForest.h"
16 #include "llvm/CodeGen/MachineCodeForInstruction.h"
17 #include "llvm/Function.h"
18 #include "llvm/iTerminators.h"
19 #include "llvm/iMemory.h"
20 #include "llvm/Constant.h"
21 #include "llvm/Type.h"
22 #include "llvm/CodeGen/MachineInstr.h"
23 #include "Support/STLExtras.h"
27 //------------------------------------------------------------------------
28 // class InstrTreeNode
29 //------------------------------------------------------------------------
32 InstrTreeNode::dump(int dumpChildren, int indent) const
39 LeftChild->dump(dumpChildren, indent+1);
41 RightChild->dump(dumpChildren, indent+1);
46 InstructionNode::InstructionNode(Instruction* I)
47 : InstrTreeNode(NTInstructionNode, I),
48 codeIsFoldedIntoParent(false)
50 opLabel = I->getOpcode();
52 // Distinguish special cases of some instructions such as Ret and Br
54 if (opLabel == Instruction::Ret && cast<ReturnInst>(I)->getReturnValue())
56 opLabel = RetValueOp; // ret(value) operation
58 else if (opLabel ==Instruction::Br && !cast<BranchInst>(I)->isUnconditional())
60 opLabel = BrCondOp; // br(cond) operation
62 else if (opLabel >= Instruction::SetEQ && opLabel <= Instruction::SetGT)
64 opLabel = SetCCOp; // common label for all SetCC ops
66 else if (opLabel == Instruction::Alloca && I->getNumOperands() > 0)
68 opLabel = AllocaN; // Alloca(ptr, N) operation
70 else if ((opLabel == Instruction::Load ||
71 opLabel == Instruction::GetElementPtr) &&
72 cast<MemAccessInst>(I)->hasIndices())
74 opLabel = opLabel + 100; // load/getElem with index vector
76 else if (opLabel == Instruction::Xor &&
77 BinaryOperator::isNot(I))
79 opLabel = (I->getType() == Type::BoolTy)? NotOp // boolean Not operator
80 : BNotOp; // bitwise Not operator
82 else if (opLabel == Instruction::And ||
83 opLabel == Instruction::Or ||
84 opLabel == Instruction::Xor)
86 // Distinguish bitwise operators from logical operators!
87 if (I->getType() != Type::BoolTy)
88 opLabel = opLabel + 100; // bitwise operator
90 else if (opLabel == Instruction::Cast)
92 const Type *ITy = I->getType();
93 switch(ITy->getPrimitiveID())
95 case Type::BoolTyID: opLabel = ToBoolTy; break;
96 case Type::UByteTyID: opLabel = ToUByteTy; break;
97 case Type::SByteTyID: opLabel = ToSByteTy; break;
98 case Type::UShortTyID: opLabel = ToUShortTy; break;
99 case Type::ShortTyID: opLabel = ToShortTy; break;
100 case Type::UIntTyID: opLabel = ToUIntTy; break;
101 case Type::IntTyID: opLabel = ToIntTy; break;
102 case Type::ULongTyID: opLabel = ToULongTy; break;
103 case Type::LongTyID: opLabel = ToLongTy; break;
104 case Type::FloatTyID: opLabel = ToFloatTy; break;
105 case Type::DoubleTyID: opLabel = ToDoubleTy; break;
106 case Type::ArrayTyID: opLabel = ToArrayTy; break;
107 case Type::PointerTyID: opLabel = ToPointerTy; break;
109 // Just use `Cast' opcode otherwise. It's probably ignored.
117 InstructionNode::dumpNode(int indent) const
119 for (int i=0; i < indent; i++)
122 cerr << getInstruction()->getOpcodeName();
123 const MachineCodeForInstruction &mvec =
124 MachineCodeForInstruction::get(getInstruction());
127 cerr << "\tMachine Instructions: ";
129 for (unsigned i = 0; i < mvec.size(); ++i) {
131 if (i < mvec.size() - 1)
140 VRegListNode::dumpNode(int indent) const
142 for (int i=0; i < indent; i++)
145 cerr << "List" << "\n";
150 VRegNode::dumpNode(int indent) const
152 for (int i=0; i < indent; i++)
155 cerr << "VReg " << getValue() << "\t(type "
156 << (int) getValue()->getValueType() << ")" << "\n";
160 ConstantNode::dumpNode(int indent) const
162 for (int i=0; i < indent; i++)
165 cerr << "Constant " << getValue() << "\t(type "
166 << (int) getValue()->getValueType() << ")" << "\n";
170 LabelNode::dumpNode(int indent) const
172 for (int i=0; i < indent; i++)
175 cerr << "Label " << getValue() << "\n";
178 //------------------------------------------------------------------------
181 // A forest of instruction trees, usually for a single method.
182 //------------------------------------------------------------------------
184 InstrForest::InstrForest(Function *F)
186 for (Function::iterator BB = F->begin(), FE = F->end(); BB != FE; ++BB) {
187 for(BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
188 buildTreeForInstruction(I);
192 InstrForest::~InstrForest()
194 for_each(treeRoots.begin(), treeRoots.end(), deleter<InstructionNode>);
198 InstrForest::dump() const
200 for (const_root_iterator I = roots_begin(); I != roots_end(); ++I)
201 (*I)->dump(/*dumpChildren*/ 1, /*indent*/ 0);
205 InstrForest::eraseRoot(InstructionNode* node)
207 for (RootSet::reverse_iterator RI=treeRoots.rbegin(), RE=treeRoots.rend();
210 treeRoots.erase(RI.base()-1);
214 InstrForest::noteTreeNodeForInstr(Instruction *instr,
215 InstructionNode *treeNode)
217 assert(treeNode->getNodeType() == InstrTreeNode::NTInstructionNode);
218 (*this)[instr] = treeNode;
219 treeRoots.push_back(treeNode); // mark node as root of a new tree
224 InstrForest::setLeftChild(InstrTreeNode *parent, InstrTreeNode *child)
226 parent->LeftChild = child;
227 child->Parent = parent;
228 if (child->getNodeType() == InstrTreeNode::NTInstructionNode)
229 eraseRoot((InstructionNode*) child); // no longer a tree root
233 InstrForest::setRightChild(InstrTreeNode *parent, InstrTreeNode *child)
235 parent->RightChild = child;
236 child->Parent = parent;
237 if (child->getNodeType() == InstrTreeNode::NTInstructionNode)
238 eraseRoot((InstructionNode*) child); // no longer a tree root
243 InstrForest::buildTreeForInstruction(Instruction *instr)
245 InstructionNode *treeNode = getTreeNodeForInstr(instr);
248 // treeNode has already been constructed for this instruction
249 assert(treeNode->getInstruction() == instr);
253 // Otherwise, create a new tree node for this instruction.
255 treeNode = new InstructionNode(instr);
256 noteTreeNodeForInstr(instr, treeNode);
258 if (instr->getOpcode() == Instruction::Call)
259 { // Operands of call instruction
263 // If the instruction has more than 2 instruction operands,
264 // then we need to create artificial list nodes to hold them.
265 // (Note that we only count operands that get tree nodes, and not
266 // others such as branch labels for a branch or switch instruction.)
268 // To do this efficiently, we'll walk all operands, build treeNodes
269 // for all appropriate operands and save them in an array. We then
270 // insert children at the end, creating list nodes where needed.
271 // As a performance optimization, allocate a child array only
272 // if a fixed array is too small.
275 InstrTreeNode **childArray =
276 (InstrTreeNode **)alloca(instr->getNumOperands()*sizeof(InstrTreeNode *));
279 // Walk the operands of the instruction
281 for (Instruction::op_iterator O = instr->op_begin(); O!=instr->op_end(); ++O)
285 // Check if the operand is a data value, not an branch label, type,
286 // method or module. If the operand is an address type (i.e., label
287 // or method) that is used in an non-branching operation, e.g., `add'.
288 // that should be considered a data value.
290 // Check latter condition here just to simplify the next IF.
291 bool includeAddressOperand =
292 (isa<BasicBlock>(operand) || isa<Function>(operand))
293 && !instr->isTerminator();
295 if (includeAddressOperand || isa<Instruction>(operand) ||
296 isa<Constant>(operand) || isa<Argument>(operand) ||
297 isa<GlobalVariable>(operand))
299 // This operand is a data value
301 // An instruction that computes the incoming value is added as a
302 // child of the current instruction if:
303 // the value has only a single use
304 // AND both instructions are in the same basic block.
305 // AND the current instruction is not a PHI (because the incoming
306 // value is conceptually in a predecessor block,
307 // even though it may be in the same static block)
309 // (Note that if the value has only a single use (viz., `instr'),
310 // the def of the value can be safely moved just before instr
311 // and therefore it is safe to combine these two instructions.)
313 // In all other cases, the virtual register holding the value
314 // is used directly, i.e., made a child of the instruction node.
316 InstrTreeNode* opTreeNode;
317 if (isa<Instruction>(operand) && operand->use_size() == 1 &&
318 cast<Instruction>(operand)->getParent() == instr->getParent() &&
319 instr->getOpcode() != Instruction::PHINode &&
320 instr->getOpcode() != Instruction::Call)
322 // Recursively create a treeNode for it.
323 opTreeNode = buildTreeForInstruction((Instruction*)operand);
325 else if (Constant *CPV = dyn_cast<Constant>(operand))
327 // Create a leaf node for a constant
328 opTreeNode = new ConstantNode(CPV);
332 // Create a leaf node for the virtual register
333 opTreeNode = new VRegNode(operand);
336 childArray[numChildren++] = opTreeNode;
340 //--------------------------------------------------------------------
341 // Add any selected operands as children in the tree.
342 // Certain instructions can have more than 2 in some instances (viz.,
343 // a CALL or a memory access -- LOAD, STORE, and GetElemPtr -- to an
344 // array or struct). Make the operands of every such instruction into
345 // a right-leaning binary tree with the operand nodes at the leaves
346 // and VRegList nodes as internal nodes.
347 //--------------------------------------------------------------------
349 InstrTreeNode *parent = treeNode;
353 unsigned instrOpcode = treeNode->getInstruction()->getOpcode();
354 assert(instrOpcode == Instruction::PHINode ||
355 instrOpcode == Instruction::Call ||
356 instrOpcode == Instruction::Load ||
357 instrOpcode == Instruction::Store ||
358 instrOpcode == Instruction::GetElementPtr);
361 // Insert the first child as a direct child
362 if (numChildren >= 1)
363 setLeftChild(parent, childArray[0]);
367 // Create a list node for children 2 .. N-1, if any
368 for (n = numChildren-1; n >= 2; n--)
370 // We have more than two children
371 InstrTreeNode *listNode = new VRegListNode();
372 setRightChild(parent, listNode);
373 setLeftChild(listNode, childArray[numChildren - n]);
377 // Now insert the last remaining child (if any).
378 if (numChildren >= 2)
381 setRightChild(parent, childArray[numChildren - 1]);