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.
21 // 6/28/01 - Vikram Adve - Created
23 //---------------------------------------------------------------------------
25 #include "llvm/CodeGen/InstrForest.h"
26 #include "llvm/CodeGen/MachineCodeForInstruction.h"
27 #include "llvm/Method.h"
28 #include "llvm/iTerminators.h"
29 #include "llvm/iMemory.h"
30 #include "llvm/iPHINode.h"
31 #include "llvm/ConstantVals.h"
32 #include "llvm/BasicBlock.h"
33 #include "llvm/CodeGen/MachineInstr.h"
34 #include "Support/STLExtras.h"
39 //------------------------------------------------------------------------
40 // class InstrTreeNode
41 //------------------------------------------------------------------------
44 InstrTreeNode::dump(int dumpChildren, int indent) const
51 LeftChild->dump(dumpChildren, indent+1);
53 RightChild->dump(dumpChildren, indent+1);
58 InstructionNode::InstructionNode(Instruction* I)
59 : InstrTreeNode(NTInstructionNode, I)
61 opLabel = I->getOpcode();
63 // Distinguish special cases of some instructions such as Ret and Br
65 if (opLabel == Instruction::Ret && cast<ReturnInst>(I)->getReturnValue())
67 opLabel = RetValueOp; // ret(value) operation
69 else if (opLabel ==Instruction::Br && !cast<BranchInst>(I)->isUnconditional())
71 opLabel = BrCondOp; // br(cond) operation
73 else if (opLabel >= Instruction::SetEQ && opLabel <= Instruction::SetGT)
75 opLabel = SetCCOp; // common label for all SetCC ops
77 else if (opLabel == Instruction::Alloca && I->getNumOperands() > 0)
79 opLabel = AllocaN; // Alloca(ptr, N) operation
81 else if ((opLabel == Instruction::Load ||
82 opLabel == Instruction::GetElementPtr) &&
83 cast<MemAccessInst>(I)->hasIndices())
85 opLabel = opLabel + 100; // load/getElem with index vector
87 else if (opLabel == Instruction::And ||
88 opLabel == Instruction::Or ||
89 opLabel == Instruction::Xor ||
90 opLabel == Instruction::Not)
92 // Distinguish bitwise operators from logical operators!
93 if (I->getType() != Type::BoolTy)
94 opLabel = opLabel + 100; // bitwise operator
96 else if (opLabel == Instruction::Cast)
98 const Type *ITy = I->getType();
99 switch(ITy->getPrimitiveID())
101 case Type::BoolTyID: opLabel = ToBoolTy; break;
102 case Type::UByteTyID: opLabel = ToUByteTy; break;
103 case Type::SByteTyID: opLabel = ToSByteTy; break;
104 case Type::UShortTyID: opLabel = ToUShortTy; break;
105 case Type::ShortTyID: opLabel = ToShortTy; break;
106 case Type::UIntTyID: opLabel = ToUIntTy; break;
107 case Type::IntTyID: opLabel = ToIntTy; break;
108 case Type::ULongTyID: opLabel = ToULongTy; break;
109 case Type::LongTyID: opLabel = ToLongTy; break;
110 case Type::FloatTyID: opLabel = ToFloatTy; break;
111 case Type::DoubleTyID: opLabel = ToDoubleTy; break;
112 case Type::ArrayTyID: opLabel = ToArrayTy; break;
113 case Type::PointerTyID: opLabel = ToPointerTy; break;
115 // Just use `Cast' opcode otherwise. It's probably ignored.
123 InstructionNode::dumpNode(int indent) const
125 for (int i=0; i < indent; i++)
128 cerr << getInstruction()->getOpcodeName();
129 const MachineCodeForInstruction &mvec =
130 MachineCodeForInstruction::get(getInstruction());
133 cerr << "\tMachine Instructions: ";
135 for (unsigned int i=0; i < mvec.size(); ++i) {
137 if (i < mvec.size() - 1)
146 VRegListNode::dumpNode(int indent) const
148 for (int i=0; i < indent; i++)
151 cerr << "List" << "\n";
156 VRegNode::dumpNode(int indent) const
158 for (int i=0; i < indent; i++)
161 cerr << "VReg " << getValue() << "\t(type "
162 << (int) getValue()->getValueType() << ")" << "\n";
166 ConstantNode::dumpNode(int indent) const
168 for (int i=0; i < indent; i++)
171 cerr << "Constant " << getValue() << "\t(type "
172 << (int) getValue()->getValueType() << ")" << "\n";
176 LabelNode::dumpNode(int indent) const
178 for (int i=0; i < indent; i++)
181 cerr << "Label " << getValue() << "\n";
184 //------------------------------------------------------------------------
187 // A forest of instruction trees, usually for a single method.
188 //------------------------------------------------------------------------
190 InstrForest::InstrForest(Method *M)
192 for (Method::iterator MI = M->begin(), ME = M->end(); MI != ME; ++MI) {
193 BasicBlock *BB = *MI;
194 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
195 buildTreeForInstruction(*I);
199 InstrForest::~InstrForest()
201 for (std::hash_map<const Instruction*,InstructionNode*>::iterator I = begin();
207 InstrForest::dump() const
209 for (std::hash_set<InstructionNode*>::const_iterator I = treeRoots.begin();
210 I != treeRoots.end(); ++I)
211 (*I)->dump(/*dumpChildren*/ 1, /*indent*/ 0);
215 InstrForest::noteTreeNodeForInstr(Instruction *instr,
216 InstructionNode *treeNode)
218 assert(treeNode->getNodeType() == InstrTreeNode::NTInstructionNode);
219 (*this)[instr] = treeNode;
220 treeRoots.insert(treeNode); // mark node as root of a new tree
225 InstrForest::setLeftChild(InstrTreeNode *Par, InstrTreeNode *Chld)
227 Par->LeftChild = Chld;
229 if (Chld->getNodeType() == InstrTreeNode::NTInstructionNode)
230 treeRoots.erase((InstructionNode*)Chld); // no longer a tree root
234 InstrForest::setRightChild(InstrTreeNode *Par, InstrTreeNode *Chld)
236 Par->RightChild = Chld;
238 if (Chld->getNodeType() == InstrTreeNode::NTInstructionNode)
239 treeRoots.erase((InstructionNode*)Chld); // no longer a tree root
244 InstrForest::buildTreeForInstruction(Instruction *instr)
246 InstructionNode *treeNode = getTreeNodeForInstr(instr);
249 // treeNode has already been constructed for this instruction
250 assert(treeNode->getInstruction() == instr);
254 // Otherwise, create a new tree node for this instruction.
256 treeNode = new InstructionNode(instr);
257 noteTreeNodeForInstr(instr, treeNode);
259 if (instr->getOpcode() == Instruction::Call)
260 { // Operands of call instruction
264 // If the instruction has more than 2 instruction operands,
265 // then we need to create artificial list nodes to hold them.
266 // (Note that we only count operands that get tree nodes, and not
267 // others such as branch labels for a branch or switch instruction.)
269 // To do this efficiently, we'll walk all operands, build treeNodes
270 // for all appropriate operands and save them in an array. We then
271 // insert children at the end, creating list nodes where needed.
272 // As a performance optimization, allocate a child array only
273 // if a fixed array is too small.
276 const unsigned int MAX_CHILD = 8;
277 static InstrTreeNode *fixedChildArray[MAX_CHILD];
278 InstrTreeNode **childArray =
279 (instr->getNumOperands() > MAX_CHILD)
280 ? new (InstrTreeNode*)[instr->getNumOperands()] : fixedChildArray;
283 // Walk the operands of the instruction
285 for (Instruction::op_iterator O = instr->op_begin(); O!=instr->op_end(); ++O)
289 // Check if the operand is a data value, not an branch label, type,
290 // method or module. If the operand is an address type (i.e., label
291 // or method) that is used in an non-branching operation, e.g., `add'.
292 // that should be considered a data value.
294 // Check latter condition here just to simplify the next IF.
295 bool includeAddressOperand =
296 (isa<BasicBlock>(operand) || isa<Method>(operand))
297 && !instr->isTerminator();
299 if (includeAddressOperand || isa<Instruction>(operand) ||
300 isa<Constant>(operand) || isa<MethodArgument>(operand) ||
301 isa<GlobalVariable>(operand))
303 // This operand is a data value
305 // An instruction that computes the incoming value is added as a
306 // child of the current instruction if:
307 // the value has only a single use
308 // AND both instructions are in the same basic block.
309 // AND the current instruction is not a PHI (because the incoming
310 // value is conceptually in a predecessor block,
311 // even though it may be in the same static block)
313 // (Note that if the value has only a single use (viz., `instr'),
314 // the def of the value can be safely moved just before instr
315 // and therefore it is safe to combine these two instructions.)
317 // In all other cases, the virtual register holding the value
318 // is used directly, i.e., made a child of the instruction node.
320 InstrTreeNode* opTreeNode;
321 if (isa<Instruction>(operand) && operand->use_size() == 1 &&
322 cast<Instruction>(operand)->getParent() == instr->getParent() &&
323 !isa<PHINode>(instr) &&
324 instr->getOpcode() != Instruction::Call)
326 // Recursively create a treeNode for it.
327 opTreeNode = buildTreeForInstruction((Instruction*)operand);
329 else if (Constant *CPV = dyn_cast<Constant>(operand))
331 // Create a leaf node for a constant
332 opTreeNode = new ConstantNode(CPV);
336 // Create a leaf node for the virtual register
337 opTreeNode = new VRegNode(operand);
340 childArray[numChildren++] = opTreeNode;
344 //--------------------------------------------------------------------
345 // Add any selected operands as children in the tree.
346 // Certain instructions can have more than 2 in some instances (viz.,
347 // a CALL or a memory access -- LOAD, STORE, and GetElemPtr -- to an
348 // array or struct). Make the operands of every such instruction into
349 // a right-leaning binary tree with the operand nodes at the leaves
350 // and VRegList nodes as internal nodes.
351 //--------------------------------------------------------------------
353 InstrTreeNode *parent = treeNode;
357 unsigned instrOpcode = treeNode->getInstruction()->getOpcode();
358 assert(instrOpcode == Instruction::PHINode ||
359 instrOpcode == Instruction::Call ||
360 instrOpcode == Instruction::Load ||
361 instrOpcode == Instruction::Store ||
362 instrOpcode == Instruction::GetElementPtr);
365 // Insert the first child as a direct child
366 if (numChildren >= 1)
367 setLeftChild(parent, childArray[0]);
371 // Create a list node for children 2 .. N-1, if any
372 for (n = numChildren-1; n >= 2; n--)
374 // We have more than two children
375 InstrTreeNode *listNode = new VRegListNode();
376 setRightChild(parent, listNode);
377 setLeftChild(listNode, childArray[numChildren - n]);
381 // Now insert the last remaining child (if any).
382 if (numChildren >= 2)
385 setRightChild(parent, childArray[numChildren - 1]);
388 if (childArray != fixedChildArray)
389 delete [] childArray;