1 //===- InstrSelection.cpp - Machine Independent Inst Selection Driver -----===//
3 // Machine-independent driver file for instruction selection. This file
4 // constructs a forest of BURG instruction trees and then uses the
5 // BURG-generated tree grammar (BURM) to find the optimal instruction sequences
6 // for a given machine.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/CodeGen/InstrSelection.h"
11 #include "llvm/CodeGen/InstrSelectionSupport.h"
12 #include "llvm/CodeGen/InstrForest.h"
13 #include "llvm/CodeGen/MachineCodeForInstruction.h"
14 #include "llvm/CodeGen/MachineFunction.h"
15 #include "llvm/Target/TargetRegInfo.h"
16 #include "llvm/Target/TargetMachine.h"
17 #include "llvm/Function.h"
18 #include "llvm/iPHINode.h"
19 #include "llvm/Pass.h"
20 #include "Support/CommandLine.h"
21 #include "Support/LeakDetector.h"
24 std::vector<MachineInstr*>
25 FixConstantOperandsForInstr(Instruction* vmInstr, MachineInstr* minstr,
26 TargetMachine& target);
29 //===--------------------------------------------------------------------===//
30 // SelectDebugLevel - Allow command line control over debugging.
32 enum SelectDebugLevel_t {
34 Select_PrintMachineCode,
35 Select_DebugInstTrees,
36 Select_DebugBurgTrees,
39 // Enable Debug Options to be specified on the command line
40 cl::opt<SelectDebugLevel_t>
41 SelectDebugLevel("dselect", cl::Hidden,
42 cl::desc("enable instruction selection debug information"),
44 clEnumValN(Select_NoDebugInfo, "n", "disable debug output"),
45 clEnumValN(Select_PrintMachineCode, "y", "print generated machine code"),
46 clEnumValN(Select_DebugInstTrees, "i",
47 "print debugging info for instruction selection"),
48 clEnumValN(Select_DebugBurgTrees, "b", "print burg trees"),
52 //===--------------------------------------------------------------------===//
53 // InstructionSelection Pass
55 // This is the actual pass object that drives the instruction selection
58 class InstructionSelection : public FunctionPass {
59 TargetMachine &Target;
60 void InsertCodeForPhis(Function &F);
61 void InsertPhiElimInstructions(BasicBlock *BB,
62 const vector<MachineInstr*>& CpVec);
63 void SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt);
64 void PostprocessMachineCodeForTree(InstructionNode* instrNode,
65 int ruleForNode, short* nts);
67 InstructionSelection(TargetMachine &T) : Target(T) {}
69 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
73 bool runOnFunction(Function &F);
74 virtual const char *getPassName() const { return "Instruction Selection"; }
78 TmpInstruction::TmpInstruction(MachineCodeForInstruction& mcfi,
79 Value *s1, Value *s2, const std::string &name)
80 : Instruction(s1->getType(), Instruction::UserOp1, name)
84 Operands.push_back(Use(s1, this)); // s1 must be non-null
86 Operands.push_back(Use(s2, this));
89 // TmpInstructions should not be garbage checked.
90 LeakDetector::removeGarbageObject(this);
93 // Constructor that requires the type of the temporary to be specified.
94 // Both S1 and S2 may be NULL.(
95 TmpInstruction::TmpInstruction(MachineCodeForInstruction& mcfi,
96 const Type *Ty, Value *s1, Value* s2,
97 const std::string &name)
98 : Instruction(Ty, Instruction::UserOp1, name)
102 if (s1) { Operands.push_back(Use(s1, this)); }
103 if (s2) { Operands.push_back(Use(s2, this)); }
105 // TmpInstructions should not be garbage checked.
106 LeakDetector::removeGarbageObject(this);
110 bool InstructionSelection::runOnFunction(Function &F)
113 // Build the instruction trees to be given as inputs to BURG.
115 InstrForest instrForest(&F);
117 if (SelectDebugLevel >= Select_DebugInstTrees)
119 std::cerr << "\n\n*** Input to instruction selection for function "
120 << F.getName() << "\n\n" << F
121 << "\n\n*** Instruction trees for function "
122 << F.getName() << "\n\n";
127 // Invoke BURG instruction selection for each tree
129 for (InstrForest::const_root_iterator RI = instrForest.roots_begin();
130 RI != instrForest.roots_end(); ++RI)
132 InstructionNode* basicNode = *RI;
133 assert(basicNode->parent() == NULL && "A `root' node has a parent?");
135 // Invoke BURM to label each tree node with a state
136 burm_label(basicNode);
138 if (SelectDebugLevel >= Select_DebugBurgTrees)
140 printcover(basicNode, 1, 0);
141 std::cerr << "\nCover cost == " << treecost(basicNode, 1, 0) <<"\n\n";
142 printMatches(basicNode);
145 // Then recursively walk the tree to select instructions
146 SelectInstructionsForTree(basicNode, /*goalnt*/1);
150 // Create the MachineBasicBlock records and add all of the MachineInstrs
151 // defined in the MachineCodeForInstruction objects to also live in the
152 // MachineBasicBlock objects.
154 MachineFunction &MF = MachineFunction::get(&F);
155 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
156 MachineBasicBlock *MCBB = new MachineBasicBlock(BI);
157 MF.getBasicBlockList().push_back(MCBB);
159 for (BasicBlock::iterator II = BI->begin(); II != BI->end(); ++II) {
160 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(II);
161 MCBB->insert(MCBB->end(), mvec.begin(), mvec.end());
165 // Insert phi elimination code
166 InsertCodeForPhis(F);
168 if (SelectDebugLevel >= Select_PrintMachineCode)
170 std::cerr << "\n*** Machine instructions after INSTRUCTION SELECTION\n";
171 MachineFunction::get(&F).dump();
178 //-------------------------------------------------------------------------
179 // This method inserts phi elimination code for all BBs in a method
180 //-------------------------------------------------------------------------
183 InstructionSelection::InsertCodeForPhis(Function &F)
185 // for all basic blocks in function
187 MachineFunction &MF = MachineFunction::get(&F);
188 for (MachineFunction::iterator BB = MF.begin(); BB != MF.end(); ++BB) {
189 for (BasicBlock::const_iterator IIt = BB->getBasicBlock()->begin();
190 const PHINode *PN = dyn_cast<PHINode>(IIt); ++IIt) {
191 // FIXME: This is probably wrong...
192 Value *PhiCpRes = new PHINode(PN->getType(), "PhiCp:");
194 // The leak detector shouldn't track these nodes. They are not garbage,
195 // even though their parent field is never filled in.
197 LeakDetector::removeGarbageObject(PhiCpRes);
199 // for each incoming value of the phi, insert phi elimination
201 for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) {
202 // insert the copy instruction to the predecessor BB
203 vector<MachineInstr*> mvec, CpVec;
204 Target.getRegInfo().cpValue2Value(PN->getIncomingValue(i), PhiCpRes,
206 for (vector<MachineInstr*>::iterator MI=mvec.begin();
207 MI != mvec.end(); ++MI) {
208 vector<MachineInstr*> CpVec2 =
209 FixConstantOperandsForInstr(const_cast<PHINode*>(PN), *MI, Target);
210 CpVec2.push_back(*MI);
211 CpVec.insert(CpVec.end(), CpVec2.begin(), CpVec2.end());
214 InsertPhiElimInstructions(PN->getIncomingBlock(i), CpVec);
217 vector<MachineInstr*> mvec;
218 Target.getRegInfo().cpValue2Value(PhiCpRes, const_cast<PHINode*>(PN),
220 BB->insert(BB->begin(), mvec.begin(), mvec.end());
221 } // for each Phi Instr in BB
222 } // for all BBs in function
225 //-------------------------------------------------------------------------
226 // Thid method inserts a copy instruction to a predecessor BB as a result
227 // of phi elimination.
228 //-------------------------------------------------------------------------
231 InstructionSelection::InsertPhiElimInstructions(BasicBlock *BB,
232 const vector<MachineInstr*>& CpVec)
234 Instruction *TermInst = (Instruction*)BB->getTerminator();
235 MachineCodeForInstruction &MC4Term = MachineCodeForInstruction::get(TermInst);
236 MachineInstr *FirstMIOfTerm = MC4Term.front();
237 assert (FirstMIOfTerm && "No Machine Instrs for terminator");
239 MachineFunction &MF = MachineFunction::get(BB->getParent());
241 // FIXME: if PHI instructions existed in the machine code, this would be
243 MachineBasicBlock *MBB = 0;
244 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
245 if (I->getBasicBlock() == BB) {
250 // find the position of first machine instruction generated by the
251 // terminator of this BB
252 MachineBasicBlock::iterator MCIt =
253 std::find(MBB->begin(), MBB->end(), FirstMIOfTerm);
255 assert(MCIt != MBB->end() && "Start inst of terminator not found");
257 // insert the copy instructions just before the first machine instruction
258 // generated for the terminator
259 MBB->insert(MCIt, CpVec.begin(), CpVec.end());
263 //---------------------------------------------------------------------------
264 // Function SelectInstructionsForTree
266 // Recursively walk the tree to select instructions.
267 // Do this top-down so that child instructions can exploit decisions
268 // made at the child instructions.
270 // E.g., if br(setle(reg,const)) decides the constant is 0 and uses
271 // a branch-on-integer-register instruction, then the setle node
272 // can use that information to avoid generating the SUBcc instruction.
274 // Note that this cannot be done bottom-up because setle must do this
275 // only if it is a child of the branch (otherwise, the result of setle
276 // may be used by multiple instructions).
277 //---------------------------------------------------------------------------
280 InstructionSelection::SelectInstructionsForTree(InstrTreeNode* treeRoot,
283 // Get the rule that matches this node.
285 int ruleForNode = burm_rule(treeRoot->state, goalnt);
287 if (ruleForNode == 0) {
288 std::cerr << "Could not match instruction tree for instr selection\n";
292 // Get this rule's non-terminals and the corresponding child nodes (if any)
294 short *nts = burm_nts[ruleForNode];
296 // First, select instructions for the current node and rule.
297 // (If this is a list node, not an instruction, then skip this step).
298 // This function is specific to the target architecture.
300 if (treeRoot->opLabel != VRegListOp)
302 vector<MachineInstr*> minstrVec;
304 InstructionNode* instrNode = (InstructionNode*)treeRoot;
305 assert(instrNode->getNodeType() == InstrTreeNode::NTInstructionNode);
307 GetInstructionsByRule(instrNode, ruleForNode, nts, Target, minstrVec);
309 MachineCodeForInstruction &mvec =
310 MachineCodeForInstruction::get(instrNode->getInstruction());
311 mvec.insert(mvec.end(), minstrVec.begin(), minstrVec.end());
314 // Then, recursively compile the child nodes, if any.
317 { // i.e., there is at least one kid
318 InstrTreeNode* kids[2];
319 int currentRule = ruleForNode;
320 burm_kids(treeRoot, currentRule, kids);
322 // First skip over any chain rules so that we don't visit
323 // the current node again.
325 while (ThisIsAChainRule(currentRule))
327 currentRule = burm_rule(treeRoot->state, nts[0]);
328 nts = burm_nts[currentRule];
329 burm_kids(treeRoot, currentRule, kids);
332 // Now we have the first non-chain rule so we have found
333 // the actual child nodes. Recursively compile them.
335 for (unsigned i = 0; nts[i]; i++)
338 InstrTreeNode::InstrTreeNodeType nodeType = kids[i]->getNodeType();
339 if (nodeType == InstrTreeNode::NTVRegListNode ||
340 nodeType == InstrTreeNode::NTInstructionNode)
341 SelectInstructionsForTree(kids[i], nts[i]);
345 // Finally, do any post-processing on this node after its children
346 // have been translated
348 if (treeRoot->opLabel != VRegListOp)
349 PostprocessMachineCodeForTree((InstructionNode*)treeRoot, ruleForNode, nts);
352 //---------------------------------------------------------------------------
353 // Function PostprocessMachineCodeForTree
355 // Apply any final cleanups to machine code for the root of a subtree
356 // after selection for all its children has been completed.
359 InstructionSelection::PostprocessMachineCodeForTree(InstructionNode* instrNode,
363 // Fix up any constant operands in the machine instructions to either
364 // use an immediate field or to load the constant into a register
365 // Walk backwards and use direct indexes to allow insertion before current
367 Instruction* vmInstr = instrNode->getInstruction();
368 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(vmInstr);
369 for (unsigned i = mvec.size(); i != 0; --i)
371 vector<MachineInstr*> loadConstVec =
372 FixConstantOperandsForInstr(vmInstr, mvec[i-1], Target);
374 mvec.insert(mvec.begin()+i-1, loadConstVec.begin(), loadConstVec.end());
380 //===----------------------------------------------------------------------===//
381 // createInstructionSelectionPass - Public entrypoint for instruction selection
382 // and this file as a whole...
384 FunctionPass *createInstructionSelectionPass(TargetMachine &T) {
385 return new InstructionSelection(T);