//===- InstrSelection.cpp - Machine Independant Inst Selection Driver -----===// // // Machine-independent driver file for instruction selection. This file // constructs a forest of BURG instruction trees and then uses the // BURG-generated tree grammar (BURM) to find the optimal instruction sequences // for a given machine. // //===----------------------------------------------------------------------===// #include "llvm/CodeGen/InstrSelection.h" #include "llvm/CodeGen/InstrSelectionSupport.h" #include "llvm/CodeGen/InstrForest.h" #include "llvm/CodeGen/MachineCodeForInstruction.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/Target/MachineRegInfo.h" #include "llvm/Target/TargetMachine.h" #include "llvm/Function.h" #include "llvm/iPHINode.h" #include "llvm/Pass.h" #include "Support/CommandLine.h" #include "Support/LeakDetector.h" using std::cerr; using std::vector; namespace { //===--------------------------------------------------------------------===// // SelectDebugLevel - Allow command line control over debugging. // enum SelectDebugLevel_t { Select_NoDebugInfo, Select_PrintMachineCode, Select_DebugInstTrees, Select_DebugBurgTrees, }; // Enable Debug Options to be specified on the command line cl::opt SelectDebugLevel("dselect", cl::Hidden, cl::desc("enable instruction selection debug information"), cl::values( clEnumValN(Select_NoDebugInfo, "n", "disable debug output"), clEnumValN(Select_PrintMachineCode, "y", "print generated machine code"), clEnumValN(Select_DebugInstTrees, "i", "print debugging info for instruction selection"), clEnumValN(Select_DebugBurgTrees, "b", "print burg trees"), 0)); //===--------------------------------------------------------------------===// // InstructionSelection Pass // // This is the actual pass object that drives the instruction selection // process. // class InstructionSelection : public FunctionPass { TargetMachine &Target; void InsertCodeForPhis(Function &F); void InsertPhiElimInstructions(BasicBlock *BB, const vector& CpVec); void SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt); void PostprocessMachineCodeForTree(InstructionNode* instrNode, int ruleForNode, short* nts); public: InstructionSelection(TargetMachine &T) : Target(T) {} virtual void getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesCFG(); } bool runOnFunction(Function &F); }; } // Register the pass... static RegisterLLC X("instselect", "Instruction Selection", createInstructionSelectionPass); TmpInstruction::TmpInstruction(Value *s1, Value *s2, const std::string &name) : Instruction(s1->getType(), Instruction::UserOp1, name) { Operands.push_back(Use(s1, this)); // s1 must be nonnull if (s2) { Operands.push_back(Use(s2, this)); } // TmpInstructions should not be garbage checked. LeakDetector::removeGarbageObject(this); } // Constructor that requires the type of the temporary to be specified. // Both S1 and S2 may be NULL.( TmpInstruction::TmpInstruction(const Type *Ty, Value *s1, Value* s2, const std::string &name) : Instruction(Ty, Instruction::UserOp1, name) { if (s1) { Operands.push_back(Use(s1, this)); } if (s2) { Operands.push_back(Use(s2, this)); } // TmpInstructions should not be garbage checked. LeakDetector::removeGarbageObject(this); } bool InstructionSelection::runOnFunction(Function &F) { // // Build the instruction trees to be given as inputs to BURG. // InstrForest instrForest(&F); if (SelectDebugLevel >= Select_DebugInstTrees) { cerr << "\n\n*** Input to instruction selection for function " << F.getName() << "\n\n" << F << "\n\n*** Instruction trees for function " << F.getName() << "\n\n"; instrForest.dump(); } // // Invoke BURG instruction selection for each tree // for (InstrForest::const_root_iterator RI = instrForest.roots_begin(); RI != instrForest.roots_end(); ++RI) { InstructionNode* basicNode = *RI; assert(basicNode->parent() == NULL && "A `root' node has a parent?"); // Invoke BURM to label each tree node with a state burm_label(basicNode); if (SelectDebugLevel >= Select_DebugBurgTrees) { printcover(basicNode, 1, 0); cerr << "\nCover cost == " << treecost(basicNode, 1, 0) << "\n\n"; printMatches(basicNode); } // Then recursively walk the tree to select instructions SelectInstructionsForTree(basicNode, /*goalnt*/1); } // // Create the MachineBasicBlock records and add all of the MachineInstrs // defined in the MachineCodeForInstruction objects to also live in the // MachineBasicBlock objects. // MachineFunction &MF = MachineFunction::get(&F); for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) { MachineBasicBlock *MCBB = new MachineBasicBlock(BI); MF.getBasicBlockList().push_back(MCBB); for (BasicBlock::iterator II = BI->begin(); II != BI->end(); ++II) { MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(II); MCBB->insert(MCBB->end(), mvec.begin(), mvec.end()); } } // Insert phi elimination code InsertCodeForPhis(F); if (SelectDebugLevel >= Select_PrintMachineCode) { cerr << "\n*** Machine instructions after INSTRUCTION SELECTION\n"; MachineFunction::get(&F).dump(); } return true; } //------------------------------------------------------------------------- // This method inserts phi elimination code for all BBs in a method //------------------------------------------------------------------------- void InstructionSelection::InsertCodeForPhis(Function &F) { // for all basic blocks in function // MachineFunction &MF = MachineFunction::get(&F); for (MachineFunction::iterator BB = MF.begin(); BB != MF.end(); ++BB) { for (BasicBlock::iterator IIt = BB->getBasicBlock()->begin(); PHINode *PN = dyn_cast(&*IIt); ++IIt) { // FIXME: This is probably wrong... Value *PhiCpRes = new PHINode(PN->getType(), "PhiCp:"); // The leak detector shouldn't track these nodes. They are not garbage, // even though their parent field is never filled in. // LeakDetector::removeGarbageObject(PhiCpRes); // for each incoming value of the phi, insert phi elimination // for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) { // insert the copy instruction to the predecessor BB vector mvec, CpVec; Target.getRegInfo().cpValue2Value(PN->getIncomingValue(i), PhiCpRes, mvec); for (vector::iterator MI=mvec.begin(); MI != mvec.end(); ++MI) { vector CpVec2 = FixConstantOperandsForInstr(PN, *MI, Target); CpVec2.push_back(*MI); CpVec.insert(CpVec.end(), CpVec2.begin(), CpVec2.end()); } InsertPhiElimInstructions(PN->getIncomingBlock(i), CpVec); } vector mvec; Target.getRegInfo().cpValue2Value(PhiCpRes, PN, mvec); BB->insert(BB->begin(), mvec.begin(), mvec.end()); } // for each Phi Instr in BB } // for all BBs in function } //------------------------------------------------------------------------- // Thid method inserts a copy instruction to a predecessor BB as a result // of phi elimination. //------------------------------------------------------------------------- void InstructionSelection::InsertPhiElimInstructions(BasicBlock *BB, const vector& CpVec) { Instruction *TermInst = (Instruction*)BB->getTerminator(); MachineCodeForInstruction &MC4Term = MachineCodeForInstruction::get(TermInst); MachineInstr *FirstMIOfTerm = MC4Term.front(); assert (FirstMIOfTerm && "No Machine Instrs for terminator"); MachineFunction &MF = MachineFunction::get(BB->getParent()); MachineBasicBlock *MBB; // FIXME: if PHI instructions existed in the machine code, this would be // unnecesary. for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) if (I->getBasicBlock() == BB) { MBB = I; break; } // find the position of first machine instruction generated by the // terminator of this BB MachineBasicBlock::iterator MCIt = std::find(MBB->begin(), MBB->end(), FirstMIOfTerm); assert(MCIt != MBB->end() && "Start inst of terminator not found"); // insert the copy instructions just before the first machine instruction // generated for the terminator MBB->insert(MCIt, CpVec.begin(), CpVec.end()); } //--------------------------------------------------------------------------- // Function SelectInstructionsForTree // // Recursively walk the tree to select instructions. // Do this top-down so that child instructions can exploit decisions // made at the child instructions. // // E.g., if br(setle(reg,const)) decides the constant is 0 and uses // a branch-on-integer-register instruction, then the setle node // can use that information to avoid generating the SUBcc instruction. // // Note that this cannot be done bottom-up because setle must do this // only if it is a child of the branch (otherwise, the result of setle // may be used by multiple instructions). //--------------------------------------------------------------------------- void InstructionSelection::SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt) { // Get the rule that matches this node. // int ruleForNode = burm_rule(treeRoot->state, goalnt); if (ruleForNode == 0) { cerr << "Could not match instruction tree for instr selection\n"; abort(); } // Get this rule's non-terminals and the corresponding child nodes (if any) // short *nts = burm_nts[ruleForNode]; // First, select instructions for the current node and rule. // (If this is a list node, not an instruction, then skip this step). // This function is specific to the target architecture. // if (treeRoot->opLabel != VRegListOp) { vector minstrVec; InstructionNode* instrNode = (InstructionNode*)treeRoot; assert(instrNode->getNodeType() == InstrTreeNode::NTInstructionNode); GetInstructionsByRule(instrNode, ruleForNode, nts, Target, minstrVec); MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(instrNode->getInstruction()); mvec.insert(mvec.end(), minstrVec.begin(), minstrVec.end()); } // Then, recursively compile the child nodes, if any. // if (nts[0]) { // i.e., there is at least one kid InstrTreeNode* kids[2]; int currentRule = ruleForNode; burm_kids(treeRoot, currentRule, kids); // First skip over any chain rules so that we don't visit // the current node again. // while (ThisIsAChainRule(currentRule)) { currentRule = burm_rule(treeRoot->state, nts[0]); nts = burm_nts[currentRule]; burm_kids(treeRoot, currentRule, kids); } // Now we have the first non-chain rule so we have found // the actual child nodes. Recursively compile them. // for (unsigned i = 0; nts[i]; i++) { assert(i < 2); InstrTreeNode::InstrTreeNodeType nodeType = kids[i]->getNodeType(); if (nodeType == InstrTreeNode::NTVRegListNode || nodeType == InstrTreeNode::NTInstructionNode) SelectInstructionsForTree(kids[i], nts[i]); } } // Finally, do any postprocessing on this node after its children // have been translated // if (treeRoot->opLabel != VRegListOp) PostprocessMachineCodeForTree((InstructionNode*)treeRoot, ruleForNode, nts); } //--------------------------------------------------------------------------- // Function PostprocessMachineCodeForTree // // Apply any final cleanups to machine code for the root of a subtree // after selection for all its children has been completed. // void InstructionSelection::PostprocessMachineCodeForTree(InstructionNode* instrNode, int ruleForNode, short* nts) { // Fix up any constant operands in the machine instructions to either // use an immediate field or to load the constant into a register // Walk backwards and use direct indexes to allow insertion before current // Instruction* vmInstr = instrNode->getInstruction(); MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(vmInstr); for (unsigned i = mvec.size(); i != 0; --i) { vector loadConstVec = FixConstantOperandsForInstr(vmInstr, mvec[i-1], Target); mvec.insert(mvec.begin()+i-1, loadConstVec.begin(), loadConstVec.end()); } } //===----------------------------------------------------------------------===// // createInstructionSelectionPass - Public entrypoint for instruction selection // and this file as a whole... // Pass *createInstructionSelectionPass(TargetMachine &T) { return new InstructionSelection(T); }