llvm-6502/lib/CodeGen/InstrSelection/InstrForest.cpp
2001-11-14 11:27:58 +00:00

386 lines
12 KiB
C++

// $Id$
//---------------------------------------------------------------------------
// File:
// InstrForest.cpp
//
// Purpose:
// Convert SSA graph to instruction trees for instruction selection.
//
// Strategy:
// The key goal is to group instructions into a single
// tree if one or more of them might be potentially combined into a single
// complex instruction in the target machine.
// Since this grouping is completely machine-independent, we do it as
// aggressive as possible to exploit any possible taret instructions.
// In particular, we group two instructions O and I if:
// (1) Instruction O computes an operand used by instruction I,
// and (2) O and I are part of the same basic block,
// and (3) O has only a single use, viz., I.
//
// History:
// 6/28/01 - Vikram Adve - Created
//
//---------------------------------------------------------------------------
#include "llvm/CodeGen/InstrForest.h"
#include "llvm/Method.h"
#include "llvm/iTerminators.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/ConstPoolVals.h"
#include "llvm/BasicBlock.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/Support/STLExtras.h"
//------------------------------------------------------------------------
// class InstrTreeNode
//------------------------------------------------------------------------
void
InstrTreeNode::dump(int dumpChildren, int indent) const
{
dumpNode(indent);
if (dumpChildren)
{
if (LeftChild)
LeftChild->dump(dumpChildren, indent+1);
if (RightChild)
RightChild->dump(dumpChildren, indent+1);
}
}
InstructionNode::InstructionNode(Instruction* I)
: InstrTreeNode(NTInstructionNode, I)
{
opLabel = I->getOpcode();
// Distinguish special cases of some instructions such as Ret and Br
//
if (opLabel == Instruction::Ret && cast<ReturnInst>(I)->getReturnValue())
{
opLabel = RetValueOp; // ret(value) operation
}
else if (opLabel ==Instruction::Br && !cast<BranchInst>(I)->isUnconditional())
{
opLabel = BrCondOp; // br(cond) operation
}
else if (opLabel >= Instruction::SetEQ && opLabel <= Instruction::SetGT)
{
opLabel = SetCCOp; // common label for all SetCC ops
}
else if (opLabel == Instruction::Alloca && I->getNumOperands() > 0)
{
opLabel = AllocaN; // Alloca(ptr, N) operation
}
else if ((opLabel == Instruction::Load ||
opLabel == Instruction::GetElementPtr) &&
cast<MemAccessInst>(I)->hasIndices())
{
opLabel = opLabel + 100; // load/getElem with index vector
}
else if (opLabel == Instruction::And ||
opLabel == Instruction::Or ||
opLabel == Instruction::Xor ||
opLabel == Instruction::Not)
{
// Distinguish bitwise operators from logical operators!
if (I->getType() != Type::BoolTy)
opLabel = opLabel + 100; // bitwise operator
}
else if (opLabel == Instruction::Cast)
{
const Type *ITy = I->getType();
switch(ITy->getPrimitiveID())
{
case Type::BoolTyID: opLabel = ToBoolTy; break;
case Type::UByteTyID: opLabel = ToUByteTy; break;
case Type::SByteTyID: opLabel = ToSByteTy; break;
case Type::UShortTyID: opLabel = ToUShortTy; break;
case Type::ShortTyID: opLabel = ToShortTy; break;
case Type::UIntTyID: opLabel = ToUIntTy; break;
case Type::IntTyID: opLabel = ToIntTy; break;
case Type::ULongTyID: opLabel = ToULongTy; break;
case Type::LongTyID: opLabel = ToLongTy; break;
case Type::FloatTyID: opLabel = ToFloatTy; break;
case Type::DoubleTyID: opLabel = ToDoubleTy; break;
case Type::ArrayTyID: opLabel = ToArrayTy; break;
case Type::PointerTyID: opLabel = ToPointerTy; break;
default:
// Just use `Cast' opcode otherwise. It's probably ignored.
break;
}
}
}
void
InstructionNode::dumpNode(int indent) const
{
for (int i=0; i < indent; i++)
cout << " ";
cout << getInstruction()->getOpcodeName();
const vector<MachineInstr*> &mvec = getInstruction()->getMachineInstrVec();
if (mvec.size() > 0)
cout << "\tMachine Instructions: ";
for (unsigned int i=0; i < mvec.size(); i++)
{
mvec[i]->dump(0);
if (i < mvec.size() - 1)
cout << "; ";
}
cout << endl;
}
void
VRegListNode::dumpNode(int indent) const
{
for (int i=0; i < indent; i++)
cout << " ";
cout << "List" << endl;
}
void
VRegNode::dumpNode(int indent) const
{
for (int i=0; i < indent; i++)
cout << " ";
cout << "VReg " << getValue() << "\t(type "
<< (int) getValue()->getValueType() << ")" << endl;
}
void
ConstantNode::dumpNode(int indent) const
{
for (int i=0; i < indent; i++)
cout << " ";
cout << "Constant " << getValue() << "\t(type "
<< (int) getValue()->getValueType() << ")" << endl;
}
void
LabelNode::dumpNode(int indent) const
{
for (int i=0; i < indent; i++)
cout << " ";
cout << "Label " << getValue() << endl;
}
//------------------------------------------------------------------------
// class InstrForest
//
// A forest of instruction trees, usually for a single method.
//------------------------------------------------------------------------
InstrForest::InstrForest(Method *M)
{
for (Method::inst_iterator I = M->inst_begin(); I != M->inst_end(); ++I)
this->buildTreeForInstruction(*I);
}
InstrForest::~InstrForest()
{
for (hash_map<const Instruction*, InstructionNode*>:: iterator I = begin();
I != end(); ++I)
delete (*I).second;
}
void
InstrForest::dump() const
{
for (hash_set<InstructionNode*>::const_iterator I = treeRoots.begin();
I != treeRoots.end(); ++I)
(*I)->dump(/*dumpChildren*/ 1, /*indent*/ 0);
}
inline void
InstrForest::noteTreeNodeForInstr(Instruction *instr,
InstructionNode *treeNode)
{
assert(treeNode->getNodeType() == InstrTreeNode::NTInstructionNode);
(*this)[instr] = treeNode;
treeRoots.insert(treeNode); // mark node as root of a new tree
}
inline void
InstrForest::setLeftChild(InstrTreeNode *Par, InstrTreeNode *Chld)
{
Par->LeftChild = Chld;
Chld->Parent = Par;
if (Chld->getNodeType() == InstrTreeNode::NTInstructionNode)
treeRoots.erase((InstructionNode*)Chld); // no longer a tree root
}
inline void
InstrForest::setRightChild(InstrTreeNode *Par, InstrTreeNode *Chld)
{
Par->RightChild = Chld;
Chld->Parent = Par;
if (Chld->getNodeType() == InstrTreeNode::NTInstructionNode)
treeRoots.erase((InstructionNode*)Chld); // no longer a tree root
}
InstructionNode*
InstrForest::buildTreeForInstruction(Instruction *instr)
{
InstructionNode *treeNode = getTreeNodeForInstr(instr);
if (treeNode)
{
// treeNode has already been constructed for this instruction
assert(treeNode->getInstruction() == instr);
return treeNode;
}
// Otherwise, create a new tree node for this instruction.
//
treeNode = new InstructionNode(instr);
noteTreeNodeForInstr(instr, treeNode);
if (instr->getOpcode() == Instruction::Call)
{ // Operands of call instruction
return treeNode;
}
// If the instruction has more than 2 instruction operands,
// then we need to create artificial list nodes to hold them.
// (Note that we only count operands that get tree nodes, and not
// others such as branch labels for a branch or switch instruction.)
//
// To do this efficiently, we'll walk all operands, build treeNodes
// for all appropriate operands and save them in an array. We then
// insert children at the end, creating list nodes where needed.
// As a performance optimization, allocate a child array only
// if a fixed array is too small.
//
int numChildren = 0;
const unsigned int MAX_CHILD = 8;
static InstrTreeNode *fixedChildArray[MAX_CHILD];
InstrTreeNode **childArray =
(instr->getNumOperands() > MAX_CHILD)
? new (InstrTreeNode*)[instr->getNumOperands()] : fixedChildArray;
//
// Walk the operands of the instruction
//
for (Instruction::op_iterator O = instr->op_begin(); O!=instr->op_end(); ++O)
{
Value* operand = *O;
// Check if the operand is a data value, not an branch label, type,
// method or module. If the operand is an address type (i.e., label
// or method) that is used in an non-branching operation, e.g., `add'.
// that should be considered a data value.
// Check latter condition here just to simplify the next IF.
bool includeAddressOperand =
(isa<BasicBlock>(operand) || isa<Method>(operand))
&& !instr->isTerminator();
if (includeAddressOperand || isa<Instruction>(operand) ||
isa<ConstPoolVal>(operand) || isa<MethodArgument>(operand) ||
isa<GlobalVariable>(operand))
{
// This operand is a data value
// An instruction that computes the incoming value is added as a
// child of the current instruction if:
// the value has only a single use
// AND both instructions are in the same basic block.
// AND the current instruction is not a PHI (because the incoming
// value is conceptually in a predecessor block,
// even though it may be in the same static block)
//
// (Note that if the value has only a single use (viz., `instr'),
// the def of the value can be safely moved just before instr
// and therefore it is safe to combine these two instructions.)
//
// In all other cases, the virtual register holding the value
// is used directly, i.e., made a child of the instruction node.
//
InstrTreeNode* opTreeNode;
if (isa<Instruction>(operand) && operand->use_size() == 1 &&
cast<Instruction>(operand)->getParent() == instr->getParent() &&
!isa<PHINode>(instr) &&
instr->getOpcode() != Instruction::Call)
{
// Recursively create a treeNode for it.
opTreeNode = buildTreeForInstruction((Instruction*)operand);
}
else if (ConstPoolVal *CPV = dyn_cast<ConstPoolVal>(operand))
{
// Create a leaf node for a constant
opTreeNode = new ConstantNode(CPV);
}
else
{
// Create a leaf node for the virtual register
opTreeNode = new VRegNode(operand);
}
childArray[numChildren++] = opTreeNode;
}
}
//--------------------------------------------------------------------
// Add any selected operands as children in the tree.
// Certain instructions can have more than 2 in some instances (viz.,
// a CALL or a memory access -- LOAD, STORE, and GetElemPtr -- to an
// array or struct). Make the operands of every such instruction into
// a right-leaning binary tree with the operand nodes at the leaves
// and VRegList nodes as internal nodes.
//--------------------------------------------------------------------
InstrTreeNode *parent = treeNode;
if (numChildren > 2)
{
unsigned instrOpcode = treeNode->getInstruction()->getOpcode();
assert(instrOpcode == Instruction::PHINode ||
instrOpcode == Instruction::Call ||
instrOpcode == Instruction::Load ||
instrOpcode == Instruction::Store ||
instrOpcode == Instruction::GetElementPtr);
}
// Insert the first child as a direct child
if (numChildren >= 1)
setLeftChild(parent, childArray[0]);
int n;
// Create a list node for children 2 .. N-1, if any
for (n = numChildren-1; n >= 2; n--)
{
// We have more than two children
InstrTreeNode *listNode = new VRegListNode();
setRightChild(parent, listNode);
setLeftChild(listNode, childArray[numChildren - n]);
parent = listNode;
}
// Now insert the last remaining child (if any).
if (numChildren >= 2)
{
assert(n == 1);
setRightChild(parent, childArray[numChildren - 1]);
}
if (childArray != fixedChildArray)
delete [] childArray;
return treeNode;
}