1 //===- InstrSelection.cpp - Machine Independent Inst Selection Driver -----===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Machine-independent driver file for instruction selection. This file
11 // constructs a forest of BURG instruction trees and then uses the
12 // BURG-generated tree grammar (BURM) to find the optimal instruction sequences
13 // for a given machine.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/CodeGen/InstrSelection.h"
18 #include "llvm/CodeGen/InstrSelectionSupport.h"
19 #include "llvm/CodeGen/InstrForest.h"
20 #include "llvm/CodeGen/MachineCodeForInstruction.h"
21 #include "llvm/CodeGen/MachineFunction.h"
22 #include "llvm/Target/TargetRegInfo.h"
23 #include "llvm/Target/TargetMachine.h"
24 #include "llvm/Function.h"
25 #include "llvm/iPHINode.h"
26 #include "llvm/Pass.h"
27 #include "Support/CommandLine.h"
28 #include "Support/LeakDetector.h"
31 std::vector<MachineInstr*>
32 FixConstantOperandsForInstr(Instruction* vmInstr, MachineInstr* minstr,
33 TargetMachine& target);
36 //===--------------------------------------------------------------------===//
37 // SelectDebugLevel - Allow command line control over debugging.
39 enum SelectDebugLevel_t {
41 Select_PrintMachineCode,
42 Select_DebugInstTrees,
43 Select_DebugBurgTrees,
46 // Enable Debug Options to be specified on the command line
47 cl::opt<SelectDebugLevel_t>
48 SelectDebugLevel("dselect", cl::Hidden,
49 cl::desc("enable instruction selection debug information"),
51 clEnumValN(Select_NoDebugInfo, "n", "disable debug output"),
52 clEnumValN(Select_PrintMachineCode, "y", "print generated machine code"),
53 clEnumValN(Select_DebugInstTrees, "i",
54 "print debugging info for instruction selection"),
55 clEnumValN(Select_DebugBurgTrees, "b", "print burg trees"),
59 //===--------------------------------------------------------------------===//
60 // InstructionSelection Pass
62 // This is the actual pass object that drives the instruction selection
65 class InstructionSelection : public FunctionPass {
66 TargetMachine &Target;
67 void InsertCodeForPhis(Function &F);
68 void InsertPhiElimInstructions(BasicBlock *BB,
69 const vector<MachineInstr*>& CpVec);
70 void SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt);
71 void PostprocessMachineCodeForTree(InstructionNode* instrNode,
72 int ruleForNode, short* nts);
74 InstructionSelection(TargetMachine &T) : Target(T) {}
76 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
80 bool runOnFunction(Function &F);
81 virtual const char *getPassName() const { return "Instruction Selection"; }
85 TmpInstruction::TmpInstruction(MachineCodeForInstruction& mcfi,
86 Value *s1, Value *s2, const std::string &name)
87 : Instruction(s1->getType(), Instruction::UserOp1, name)
91 Operands.push_back(Use(s1, this)); // s1 must be non-null
93 Operands.push_back(Use(s2, this));
96 // TmpInstructions should not be garbage checked.
97 LeakDetector::removeGarbageObject(this);
100 // Constructor that requires the type of the temporary to be specified.
101 // Both S1 and S2 may be NULL.(
102 TmpInstruction::TmpInstruction(MachineCodeForInstruction& mcfi,
103 const Type *Ty, Value *s1, Value* s2,
104 const std::string &name)
105 : Instruction(Ty, Instruction::UserOp1, name)
109 if (s1) { Operands.push_back(Use(s1, this)); }
110 if (s2) { Operands.push_back(Use(s2, this)); }
112 // TmpInstructions should not be garbage checked.
113 LeakDetector::removeGarbageObject(this);
117 bool InstructionSelection::runOnFunction(Function &F)
120 // Build the instruction trees to be given as inputs to BURG.
122 InstrForest instrForest(&F);
124 if (SelectDebugLevel >= Select_DebugInstTrees)
126 std::cerr << "\n\n*** Input to instruction selection for function "
127 << F.getName() << "\n\n" << F
128 << "\n\n*** Instruction trees for function "
129 << F.getName() << "\n\n";
134 // Invoke BURG instruction selection for each tree
136 for (InstrForest::const_root_iterator RI = instrForest.roots_begin();
137 RI != instrForest.roots_end(); ++RI)
139 InstructionNode* basicNode = *RI;
140 assert(basicNode->parent() == NULL && "A `root' node has a parent?");
142 // Invoke BURM to label each tree node with a state
143 burm_label(basicNode);
145 if (SelectDebugLevel >= Select_DebugBurgTrees)
147 printcover(basicNode, 1, 0);
148 std::cerr << "\nCover cost == " << treecost(basicNode, 1, 0) <<"\n\n";
149 printMatches(basicNode);
152 // Then recursively walk the tree to select instructions
153 SelectInstructionsForTree(basicNode, /*goalnt*/1);
157 // Create the MachineBasicBlock records and add all of the MachineInstrs
158 // defined in the MachineCodeForInstruction objects to also live in the
159 // MachineBasicBlock objects.
161 MachineFunction &MF = MachineFunction::get(&F);
162 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
163 MachineBasicBlock *MCBB = new MachineBasicBlock(BI);
164 MF.getBasicBlockList().push_back(MCBB);
166 for (BasicBlock::iterator II = BI->begin(); II != BI->end(); ++II) {
167 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(II);
168 MCBB->insert(MCBB->end(), mvec.begin(), mvec.end());
172 // Insert phi elimination code
173 InsertCodeForPhis(F);
175 if (SelectDebugLevel >= Select_PrintMachineCode)
177 std::cerr << "\n*** Machine instructions after INSTRUCTION SELECTION\n";
178 MachineFunction::get(&F).dump();
185 //-------------------------------------------------------------------------
186 // This method inserts phi elimination code for all BBs in a method
187 //-------------------------------------------------------------------------
190 InstructionSelection::InsertCodeForPhis(Function &F)
192 // for all basic blocks in function
194 MachineFunction &MF = MachineFunction::get(&F);
195 for (MachineFunction::iterator BB = MF.begin(); BB != MF.end(); ++BB) {
196 for (BasicBlock::const_iterator IIt = BB->getBasicBlock()->begin();
197 const PHINode *PN = dyn_cast<PHINode>(IIt); ++IIt) {
198 // FIXME: This is probably wrong...
199 Value *PhiCpRes = new PHINode(PN->getType(), "PhiCp:");
201 // The leak detector shouldn't track these nodes. They are not garbage,
202 // even though their parent field is never filled in.
204 LeakDetector::removeGarbageObject(PhiCpRes);
206 // for each incoming value of the phi, insert phi elimination
208 for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) {
209 // insert the copy instruction to the predecessor BB
210 vector<MachineInstr*> mvec, CpVec;
211 Target.getRegInfo().cpValue2Value(PN->getIncomingValue(i), PhiCpRes,
213 for (vector<MachineInstr*>::iterator MI=mvec.begin();
214 MI != mvec.end(); ++MI) {
215 vector<MachineInstr*> CpVec2 =
216 FixConstantOperandsForInstr(const_cast<PHINode*>(PN), *MI, Target);
217 CpVec2.push_back(*MI);
218 CpVec.insert(CpVec.end(), CpVec2.begin(), CpVec2.end());
221 InsertPhiElimInstructions(PN->getIncomingBlock(i), CpVec);
224 vector<MachineInstr*> mvec;
225 Target.getRegInfo().cpValue2Value(PhiCpRes, const_cast<PHINode*>(PN),
227 BB->insert(BB->begin(), mvec.begin(), mvec.end());
228 } // for each Phi Instr in BB
229 } // for all BBs in function
232 //-------------------------------------------------------------------------
233 // Thid method inserts a copy instruction to a predecessor BB as a result
234 // of phi elimination.
235 //-------------------------------------------------------------------------
238 InstructionSelection::InsertPhiElimInstructions(BasicBlock *BB,
239 const vector<MachineInstr*>& CpVec)
241 Instruction *TermInst = (Instruction*)BB->getTerminator();
242 MachineCodeForInstruction &MC4Term = MachineCodeForInstruction::get(TermInst);
243 MachineInstr *FirstMIOfTerm = MC4Term.front();
244 assert (FirstMIOfTerm && "No Machine Instrs for terminator");
246 MachineFunction &MF = MachineFunction::get(BB->getParent());
248 // FIXME: if PHI instructions existed in the machine code, this would be
250 MachineBasicBlock *MBB = 0;
251 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
252 if (I->getBasicBlock() == BB) {
257 // find the position of first machine instruction generated by the
258 // terminator of this BB
259 MachineBasicBlock::iterator MCIt =
260 std::find(MBB->begin(), MBB->end(), FirstMIOfTerm);
262 assert(MCIt != MBB->end() && "Start inst of terminator not found");
264 // insert the copy instructions just before the first machine instruction
265 // generated for the terminator
266 MBB->insert(MCIt, CpVec.begin(), CpVec.end());
270 //---------------------------------------------------------------------------
271 // Function SelectInstructionsForTree
273 // Recursively walk the tree to select instructions.
274 // Do this top-down so that child instructions can exploit decisions
275 // made at the child instructions.
277 // E.g., if br(setle(reg,const)) decides the constant is 0 and uses
278 // a branch-on-integer-register instruction, then the setle node
279 // can use that information to avoid generating the SUBcc instruction.
281 // Note that this cannot be done bottom-up because setle must do this
282 // only if it is a child of the branch (otherwise, the result of setle
283 // may be used by multiple instructions).
284 //---------------------------------------------------------------------------
287 InstructionSelection::SelectInstructionsForTree(InstrTreeNode* treeRoot,
290 // Get the rule that matches this node.
292 int ruleForNode = burm_rule(treeRoot->state, goalnt);
294 if (ruleForNode == 0) {
295 std::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 (unsigned i = 0; nts[i]; i++)
345 InstrTreeNode::InstrTreeNodeType nodeType = kids[i]->getNodeType();
346 if (nodeType == InstrTreeNode::NTVRegListNode ||
347 nodeType == InstrTreeNode::NTInstructionNode)
348 SelectInstructionsForTree(kids[i], nts[i]);
352 // Finally, do any post-processing on this node after its children
353 // have been translated
355 if (treeRoot->opLabel != VRegListOp)
356 PostprocessMachineCodeForTree((InstructionNode*)treeRoot, ruleForNode, nts);
359 //---------------------------------------------------------------------------
360 // Function PostprocessMachineCodeForTree
362 // Apply any final cleanups to machine code for the root of a subtree
363 // after selection for all its children has been completed.
366 InstructionSelection::PostprocessMachineCodeForTree(InstructionNode* instrNode,
370 // Fix up any constant operands in the machine instructions to either
371 // use an immediate field or to load the constant into a register
372 // Walk backwards and use direct indexes to allow insertion before current
374 Instruction* vmInstr = instrNode->getInstruction();
375 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(vmInstr);
376 for (unsigned i = mvec.size(); i != 0; --i)
378 vector<MachineInstr*> loadConstVec =
379 FixConstantOperandsForInstr(vmInstr, mvec[i-1], Target);
381 mvec.insert(mvec.begin()+i-1, loadConstVec.begin(), loadConstVec.end());
387 //===----------------------------------------------------------------------===//
388 // createInstructionSelectionPass - Public entrypoint for instruction selection
389 // and this file as a whole...
391 FunctionPass *createInstructionSelectionPass(TargetMachine &T) {
392 return new InstructionSelection(T);