2 //***************************************************************************
9 // 7/02/01 - Vikram Adve - Created
10 //**************************************************************************/
13 #include "llvm/CodeGen/InstrSelection.h"
14 #include "llvm/CodeGen/MachineInstr.h"
15 #include "llvm/Support/CommandLine.h"
16 #include "llvm/Type.h"
17 #include "llvm/iMemory.h"
18 #include "llvm/Instruction.h"
19 #include "llvm/BasicBlock.h"
20 #include "llvm/Method.h"
22 static bool SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt,
23 TargetMachine &Target);
26 enum SelectDebugLevel_t {
28 Select_PrintMachineCode,
29 Select_DebugInstTrees,
30 Select_DebugBurgTrees,
33 // Enable Debug Options to be specified on the command line
34 cl::Enum<enum SelectDebugLevel_t> SelectDebugLevel("dselect", cl::NoFlags,
35 "enable instruction selection debugging information",
36 clEnumValN(Select_NoDebugInfo, "n", "disable debug output"),
37 clEnumValN(Select_PrintMachineCode, "y", "print generated machine code"),
38 clEnumValN(Select_DebugInstTrees, "i", "print instruction selection debug info"),
39 clEnumValN(Select_DebugBurgTrees, "b", "print burg trees"), 0);
43 //---------------------------------------------------------------------------
44 // Entry point for instruction selection using BURG.
45 // Returns true if instruction selection failed, false otherwise.
46 //---------------------------------------------------------------------------
48 bool SelectInstructionsForMethod(Method* method, TargetMachine &Target) {
52 // Build the instruction trees to be given as inputs to BURG.
54 InstrForest instrForest(method);
56 if (SelectDebugLevel >= Select_DebugInstTrees)
58 cout << "\n\n*** Instruction trees for method "
59 << (method->hasName()? method->getName() : "")
65 // Invoke BURG instruction selection for each tree
67 const hash_set<InstructionNode*> &treeRoots = instrForest.getRootSet();
68 for (hash_set<InstructionNode*>::const_iterator
69 treeRootIter = treeRoots.begin(); treeRootIter != treeRoots.end();
71 InstrTreeNode* basicNode = *treeRootIter;
73 // Invoke BURM to label each tree node with a state
74 burm_label(basicNode);
76 if (SelectDebugLevel >= Select_DebugBurgTrees) {
77 printcover(basicNode, 1, 0);
78 cerr << "\nCover cost == " << treecost(basicNode, 1, 0) << "\n\n";
79 printMatches(basicNode);
82 // Then recursively walk the tree to select instructions
83 if (SelectInstructionsForTree(basicNode, /*goalnt*/1, Target)) {
90 // Record instructions in the vector for each basic block
92 for (Method::iterator BI = method->begin(); BI != method->end(); ++BI) {
93 MachineCodeForBasicBlock& bbMvec = (*BI)->getMachineInstrVec();
94 for (BasicBlock::iterator II = (*BI)->begin(); II != (*BI)->end(); ++II) {
95 MachineCodeForVMInstr& mvec = (*II)->getMachineInstrVec();
96 for (unsigned i=0; i < mvec.size(); i++)
97 bbMvec.push_back(mvec[i]);
101 if (SelectDebugLevel >= Select_PrintMachineCode) {
102 cout << endl << "*** Machine instructions after INSTRUCTION SELECTION" << endl;
103 PrintMachineInstructions(method);
110 //---------------------------------------------------------------------------
111 // Function: FoldGetElemChain
114 // Fold a chain of GetElementPtr instructions into an equivalent
115 // (Pointer, IndexVector) pair. Returns the pointer Value, and
116 // stores the resulting IndexVector in argument chainIdxVec.
117 //---------------------------------------------------------------------------
120 FoldGetElemChain(const InstructionNode* getElemInstrNode,
121 vector<ConstPoolVal*>& chainIdxVec)
123 MemAccessInst* getElemInst = (MemAccessInst*)
124 getElemInstrNode->getInstruction();
126 // Initialize return values from the incoming instruction
127 Value* ptrVal = getElemInst->getPtrOperand();
128 chainIdxVec = getElemInst->getIndexVec(); // copies index vector values
130 // Now chase the chain of getElementInstr instructions, if any
131 InstrTreeNode* ptrChild = getElemInstrNode->leftChild();
132 while (ptrChild->getOpLabel() == Instruction::GetElementPtr ||
133 ptrChild->getOpLabel() == GetElemPtrIdx)
135 // Child is a GetElemPtr instruction
136 getElemInst = (MemAccessInst*)
137 ((InstructionNode*) ptrChild)->getInstruction();
138 const vector<ConstPoolVal*>& idxVec = getElemInst->getIndexVec();
140 // Get the pointer value out of ptrChild and *prepend* its index vector
141 ptrVal = getElemInst->getPtrOperand();
142 chainIdxVec.insert(chainIdxVec.begin(), idxVec.begin(), idxVec.end());
144 ptrChild = ptrChild->leftChild();
151 //*********************** Private Functions *****************************/
154 //---------------------------------------------------------------------------
155 // Function SelectInstructionsForTree
157 // Recursively walk the tree to select instructions.
158 // Do this top-down so that child instructions can exploit decisions
159 // made at the child instructions.
161 // E.g., if br(setle(reg,const)) decides the constant is 0 and uses
162 // a branch-on-integer-register instruction, then the setle node
163 // can use that information to avoid generating the SUBcc instruction.
165 // Note that this cannot be done bottom-up because setle must do this
166 // only if it is a child of the branch (otherwise, the result of setle
167 // may be used by multiple instructions).
168 //---------------------------------------------------------------------------
170 bool SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt,
171 TargetMachine &Target) {
172 // Use a static vector to avoid allocating a new one per VM instruction
173 static MachineInstr* minstrVec[MAX_INSTR_PER_VMINSTR];
175 // Get the rule that matches this node.
177 int ruleForNode = burm_rule(treeRoot->state, goalnt);
179 if (ruleForNode == 0) {
180 cerr << "Could not match instruction tree for instr selection" << endl;
184 // Get this rule's non-terminals and the corresponding child nodes (if any)
186 short *nts = burm_nts[ruleForNode];
189 // First, select instructions for the current node and rule.
190 // (If this is a list node, not an instruction, then skip this step).
191 // This function is specific to the target architecture.
193 if (treeRoot->opLabel != VRegListOp) {
194 InstructionNode* instrNode = (InstructionNode*)treeRoot;
195 assert(instrNode->getNodeType() == InstrTreeNode::NTInstructionNode);
197 unsigned N = GetInstructionsByRule(instrNode, ruleForNode, nts, Target,
199 assert(N <= MAX_INSTR_PER_VMINSTR);
200 for (unsigned i=0; i < N; i++) {
201 assert(minstrVec[i] != NULL);
202 instrNode->getInstruction()->addMachineInstruction(minstrVec[i]);
206 // Then, recursively compile the child nodes, if any.
208 if (nts[0]) { // i.e., there is at least one kid
209 InstrTreeNode* kids[2];
210 int currentRule = ruleForNode;
211 burm_kids(treeRoot, currentRule, kids);
213 // First skip over any chain rules so that we don't visit
214 // the current node again.
216 while (ThisIsAChainRule(currentRule)) {
217 currentRule = burm_rule(treeRoot->state, nts[0]);
218 nts = burm_nts[currentRule];
219 burm_kids(treeRoot, currentRule, kids);
222 // Now we have the first non-chain rule so we have found
223 // the actual child nodes. Recursively compile them.
225 for (int i = 0; nts[i]; i++) {
227 InstrTreeNode::InstrTreeNodeType nodeType = kids[i]->getNodeType();
228 if (nodeType == InstrTreeNode::NTVRegListNode ||
229 nodeType == InstrTreeNode::NTInstructionNode) {
230 if (SelectInstructionsForTree(kids[i], nts[i], Target))
231 return true; // failure
236 return false; // success