2 //***************************************************************************
7 // Machine-independent driver file for instruction selection.
8 // This file constructs a forest of BURG instruction trees and then
9 // uses the BURG-generated tree grammar (BURM) to find the optimal
10 // instruction sequences for a given machine.
13 // 7/02/01 - Vikram Adve - Created
14 //**************************************************************************/
17 #include "llvm/CodeGen/InstrSelection.h"
18 #include "llvm/CodeGen/InstrSelectionSupport.h"
19 #include "llvm/CodeGen/MachineInstr.h"
20 #include "llvm/CodeGen/InstrForest.h"
21 #include "llvm/CodeGen/MachineCodeForInstruction.h"
22 #include "llvm/CodeGen/MachineCodeForMethod.h"
23 #include "llvm/Target/MachineRegInfo.h"
24 #include "llvm/Target/TargetMachine.h"
25 #include "llvm/BasicBlock.h"
26 #include "llvm/Function.h"
27 #include "llvm/iPHINode.h"
28 #include "Support/CommandLine.h"
32 //******************** Internal Data Declarations ************************/
35 enum SelectDebugLevel_t {
37 Select_PrintMachineCode,
38 Select_DebugInstTrees,
39 Select_DebugBurgTrees,
42 // Enable Debug Options to be specified on the command line
43 cl::Enum<enum SelectDebugLevel_t> SelectDebugLevel("dselect", cl::NoFlags,
44 "enable instruction selection debugging information",
45 clEnumValN(Select_NoDebugInfo, "n", "disable debug output"),
46 clEnumValN(Select_PrintMachineCode, "y", "print generated machine code"),
47 clEnumValN(Select_DebugInstTrees, "i", "print debugging info for instruction selection "),
48 clEnumValN(Select_DebugBurgTrees, "b", "print burg trees"), 0);
51 //******************** Forward Function Declarations ***********************/
54 static bool SelectInstructionsForTree (InstrTreeNode* treeRoot,
56 TargetMachine &target);
58 static void PostprocessMachineCodeForTree(InstructionNode* instrNode,
61 TargetMachine &target);
63 static void InsertCode4AllPhisInMeth(Function *F, TargetMachine &target);
67 //******************* Externally Visible Functions *************************/
70 //---------------------------------------------------------------------------
71 // Entry point for instruction selection using BURG.
72 // Returns true if instruction selection failed, false otherwise.
73 //---------------------------------------------------------------------------
76 SelectInstructionsForMethod(Function *F, TargetMachine &target)
81 // Build the instruction trees to be given as inputs to BURG.
83 InstrForest instrForest(F);
85 if (SelectDebugLevel >= Select_DebugInstTrees)
87 cerr << "\n\n*** Input to instruction selection for function "
88 << F->getName() << "\n\n";
91 cerr << "\n\n*** Instruction trees for function "
92 << F->getName() << "\n\n";
97 // Invoke BURG instruction selection for each tree
99 for (InstrForest::const_root_iterator RI = instrForest.roots_begin();
100 RI != instrForest.roots_end(); ++RI)
102 InstructionNode* basicNode = *RI;
103 assert(basicNode->parent() == NULL && "A `root' node has a parent?");
105 // Invoke BURM to label each tree node with a state
106 burm_label(basicNode);
108 if (SelectDebugLevel >= Select_DebugBurgTrees)
110 printcover(basicNode, 1, 0);
111 cerr << "\nCover cost == " << treecost(basicNode, 1, 0) << "\n\n";
112 printMatches(basicNode);
115 // Then recursively walk the tree to select instructions
116 if (SelectInstructionsForTree(basicNode, /*goalnt*/1, target))
124 // Record instructions in the vector for each basic block
126 for (Function::iterator BI = F->begin(), BE = F->end(); BI != BE; ++BI)
128 MachineCodeForBasicBlock& bbMvec = (*BI)->getMachineInstrVec();
129 for (BasicBlock::iterator II = (*BI)->begin(); II != (*BI)->end(); ++II)
131 MachineCodeForInstruction &mvec =MachineCodeForInstruction::get(*II);
132 for (unsigned i=0; i < mvec.size(); i++)
133 bbMvec.push_back(mvec[i]);
137 // Insert phi elimination code -- added by Ruchira
138 InsertCode4AllPhisInMeth(F, target);
141 if (SelectDebugLevel >= Select_PrintMachineCode)
143 cerr << "\n*** Machine instructions after INSTRUCTION SELECTION\n";
144 MachineCodeForMethod::get(F).dump();
151 //*********************** Private Functions *****************************/
154 //-------------------------------------------------------------------------
155 // Thid method inserts a copy instruction to a predecessor BB as a result
156 // of phi elimination.
157 //-------------------------------------------------------------------------
160 InsertPhiElimInstructions(BasicBlock *BB, const vector<MachineInstr*>& CpVec)
162 Instruction *TermInst = (Instruction*)BB->getTerminator();
163 MachineCodeForInstruction &MC4Term =MachineCodeForInstruction::get(TermInst);
164 MachineInstr *FirstMIOfTerm = *( MC4Term.begin() );
166 assert( FirstMIOfTerm && "No Machine Instrs for terminator" );
168 // get an iterator to machine instructions in the BB
169 MachineCodeForBasicBlock& bbMvec = BB->getMachineInstrVec();
170 MachineCodeForBasicBlock::iterator MCIt = bbMvec.begin();
172 // find the position of first machine instruction generated by the
173 // terminator of this BB
174 for( ; (MCIt != bbMvec.end()) && (*MCIt != FirstMIOfTerm) ; ++MCIt )
176 assert( MCIt != bbMvec.end() && "Start inst of terminator not found");
178 // insert the copy instructions just before the first machine instruction
179 // generated for the terminator
180 bbMvec.insert(MCIt, CpVec.begin(), CpVec.end());
182 //cerr << "\nPhiElimination copy inst: " << *CopyInstVec[0];
186 //-------------------------------------------------------------------------
187 // This method inserts phi elimination code for all BBs in a method
188 //-------------------------------------------------------------------------
191 InsertCode4AllPhisInMeth(Function *F, TargetMachine &target)
193 // for all basic blocks in function
195 for (Function::iterator BI = F->begin(); BI != F->end(); ++BI) {
197 BasicBlock *BB = *BI;
198 const BasicBlock::InstListType &InstList = BB->getInstList();
199 BasicBlock::InstListType::const_iterator IIt = InstList.begin();
201 // for all instructions in the basic block
203 for( ; IIt != InstList.end(); ++IIt ) {
205 if (PHINode *PN = dyn_cast<PHINode>(*IIt)) {
206 // FIXME: This is probably wrong...
207 Value *PhiCpRes = new PHINode(PN->getType(), "PhiCp:");
209 // for each incoming value of the phi, insert phi elimination
211 for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) {
212 // insert the copy instruction to the predecessor BB
214 target.getRegInfo().cpValue2Value(PN->getIncomingValue(i),
217 vector<MachineInstr*> CpVec = FixConstantOperandsForInstr(PN, CpMI,
219 CpVec.push_back(CpMI);
221 InsertPhiElimInstructions(PN->getIncomingBlock(i), CpVec);
224 MachineInstr *CpMI2 =
225 target.getRegInfo().cpValue2Value(PhiCpRes, PN);
227 // get an iterator to machine instructions in the BB
228 MachineCodeForBasicBlock& bbMvec = BB->getMachineInstrVec();
230 bbMvec.insert( bbMvec.begin(), CpMI2);
232 else break; // since PHI nodes can only be at the top
234 } // for each Phi Instr in BB
235 } // for all BBs in function
239 //---------------------------------------------------------------------------
240 // Function PostprocessMachineCodeForTree
242 // Apply any final cleanups to machine code for the root of a subtree
243 // after selection for all its children has been completed.
244 //---------------------------------------------------------------------------
247 PostprocessMachineCodeForTree(InstructionNode* instrNode,
250 TargetMachine &target)
252 // Fix up any constant operands in the machine instructions to either
253 // use an immediate field or to load the constant into a register
254 // Walk backwards and use direct indexes to allow insertion before current
256 Instruction* vmInstr = instrNode->getInstruction();
257 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(vmInstr);
258 for (int i = (int) mvec.size()-1; i >= 0; i--)
260 std::vector<MachineInstr*> loadConstVec =
261 FixConstantOperandsForInstr(vmInstr, mvec[i], target);
263 if (loadConstVec.size() > 0)
264 mvec.insert(mvec.begin()+i, loadConstVec.begin(), loadConstVec.end());
268 //---------------------------------------------------------------------------
269 // Function SelectInstructionsForTree
271 // Recursively walk the tree to select instructions.
272 // Do this top-down so that child instructions can exploit decisions
273 // made at the child instructions.
275 // E.g., if br(setle(reg,const)) decides the constant is 0 and uses
276 // a branch-on-integer-register instruction, then the setle node
277 // can use that information to avoid generating the SUBcc instruction.
279 // Note that this cannot be done bottom-up because setle must do this
280 // only if it is a child of the branch (otherwise, the result of setle
281 // may be used by multiple instructions).
282 //---------------------------------------------------------------------------
285 SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt,
286 TargetMachine &target)
288 // Get the rule that matches this node.
290 int ruleForNode = burm_rule(treeRoot->state, goalnt);
292 if (ruleForNode == 0)
294 cerr << "Could not match instruction tree for instr selection\n";
299 // Get this rule's non-terminals and the corresponding child nodes (if any)
301 short *nts = burm_nts[ruleForNode];
303 // First, select instructions for the current node and rule.
304 // (If this is a list node, not an instruction, then skip this step).
305 // This function is specific to the target architecture.
307 if (treeRoot->opLabel != VRegListOp)
309 vector<MachineInstr*> minstrVec;
311 InstructionNode* instrNode = (InstructionNode*)treeRoot;
312 assert(instrNode->getNodeType() == InstrTreeNode::NTInstructionNode);
314 GetInstructionsByRule(instrNode, ruleForNode, nts, target, minstrVec);
316 MachineCodeForInstruction &mvec =
317 MachineCodeForInstruction::get(instrNode->getInstruction());
318 mvec.insert(mvec.end(), minstrVec.begin(), minstrVec.end());
321 // Then, recursively compile the child nodes, if any.
324 { // i.e., there is at least one kid
325 InstrTreeNode* kids[2];
326 int currentRule = ruleForNode;
327 burm_kids(treeRoot, currentRule, kids);
329 // First skip over any chain rules so that we don't visit
330 // the current node again.
332 while (ThisIsAChainRule(currentRule))
334 currentRule = burm_rule(treeRoot->state, nts[0]);
335 nts = burm_nts[currentRule];
336 burm_kids(treeRoot, currentRule, kids);
339 // Now we have the first non-chain rule so we have found
340 // the actual child nodes. Recursively compile them.
342 for (int i = 0; nts[i]; i++)
345 InstrTreeNode::InstrTreeNodeType nodeType = kids[i]->getNodeType();
346 if (nodeType == InstrTreeNode::NTVRegListNode ||
347 nodeType == InstrTreeNode::NTInstructionNode)
349 if (SelectInstructionsForTree(kids[i], nts[i], target))
350 return true; // failure
355 // Finally, do any postprocessing on this node after its children
356 // have been translated
358 if (treeRoot->opLabel != VRegListOp)
360 InstructionNode* instrNode = (InstructionNode*)treeRoot;
361 PostprocessMachineCodeForTree(instrNode, ruleForNode, nts, target);
364 return false; // success