1 //===- InstrSelection.cpp - Machine Independant 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);
77 // Register the pass...
78 static RegisterLLC<InstructionSelection>
79 X("instselect", "Instruction Selection", createInstructionSelectionPass);
81 TmpInstruction::TmpInstruction(Value *s1, Value *s2, const std::string &name)
82 : Instruction(s1->getType(), Instruction::UserOp1, name) {
83 Operands.push_back(Use(s1, this)); // s1 must be nonnull
85 Operands.push_back(Use(s2, this));
88 // TmpInstructions should not be garbage checked.
89 LeakDetector::removeGarbageObject(this);
92 // Constructor that requires the type of the temporary to be specified.
93 // Both S1 and S2 may be NULL.(
94 TmpInstruction::TmpInstruction(const Type *Ty, Value *s1, Value* s2,
95 const std::string &name)
96 : Instruction(Ty, Instruction::UserOp1, name) {
97 if (s1) { Operands.push_back(Use(s1, this)); }
98 if (s2) { Operands.push_back(Use(s2, this)); }
100 // TmpInstructions should not be garbage checked.
101 LeakDetector::removeGarbageObject(this);
105 bool InstructionSelection::runOnFunction(Function &F)
108 // Build the instruction trees to be given as inputs to BURG.
110 InstrForest instrForest(&F);
112 if (SelectDebugLevel >= Select_DebugInstTrees)
114 std::cerr << "\n\n*** Input to instruction selection for function "
115 << F.getName() << "\n\n" << F
116 << "\n\n*** Instruction trees for function "
117 << F.getName() << "\n\n";
122 // Invoke BURG instruction selection for each tree
124 for (InstrForest::const_root_iterator RI = instrForest.roots_begin();
125 RI != instrForest.roots_end(); ++RI)
127 InstructionNode* basicNode = *RI;
128 assert(basicNode->parent() == NULL && "A `root' node has a parent?");
130 // Invoke BURM to label each tree node with a state
131 burm_label(basicNode);
133 if (SelectDebugLevel >= Select_DebugBurgTrees)
135 printcover(basicNode, 1, 0);
136 std::cerr << "\nCover cost == " << treecost(basicNode, 1, 0) <<"\n\n";
137 printMatches(basicNode);
140 // Then recursively walk the tree to select instructions
141 SelectInstructionsForTree(basicNode, /*goalnt*/1);
145 // Create the MachineBasicBlock records and add all of the MachineInstrs
146 // defined in the MachineCodeForInstruction objects to also live in the
147 // MachineBasicBlock objects.
149 MachineFunction &MF = MachineFunction::get(&F);
150 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
151 MachineBasicBlock *MCBB = new MachineBasicBlock(BI);
152 MF.getBasicBlockList().push_back(MCBB);
154 for (BasicBlock::iterator II = BI->begin(); II != BI->end(); ++II) {
155 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(II);
156 MCBB->insert(MCBB->end(), mvec.begin(), mvec.end());
160 // Insert phi elimination code
161 InsertCodeForPhis(F);
163 if (SelectDebugLevel >= Select_PrintMachineCode)
165 std::cerr << "\n*** Machine instructions after INSTRUCTION SELECTION\n";
166 MachineFunction::get(&F).dump();
173 //-------------------------------------------------------------------------
174 // This method inserts phi elimination code for all BBs in a method
175 //-------------------------------------------------------------------------
178 InstructionSelection::InsertCodeForPhis(Function &F)
180 // for all basic blocks in function
182 MachineFunction &MF = MachineFunction::get(&F);
183 for (MachineFunction::iterator BB = MF.begin(); BB != MF.end(); ++BB) {
184 for (BasicBlock::iterator IIt = BB->getBasicBlock()->begin();
185 PHINode *PN = dyn_cast<PHINode>(&*IIt); ++IIt) {
186 // FIXME: This is probably wrong...
187 Value *PhiCpRes = new PHINode(PN->getType(), "PhiCp:");
189 // The leak detector shouldn't track these nodes. They are not garbage,
190 // even though their parent field is never filled in.
192 LeakDetector::removeGarbageObject(PhiCpRes);
194 // for each incoming value of the phi, insert phi elimination
196 for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) {
197 // insert the copy instruction to the predecessor BB
198 vector<MachineInstr*> mvec, CpVec;
199 Target.getRegInfo().cpValue2Value(PN->getIncomingValue(i), PhiCpRes,
201 for (vector<MachineInstr*>::iterator MI=mvec.begin();
202 MI != mvec.end(); ++MI) {
203 vector<MachineInstr*> CpVec2 =
204 FixConstantOperandsForInstr(PN, *MI, Target);
205 CpVec2.push_back(*MI);
206 CpVec.insert(CpVec.end(), CpVec2.begin(), CpVec2.end());
209 InsertPhiElimInstructions(PN->getIncomingBlock(i), CpVec);
212 vector<MachineInstr*> mvec;
213 Target.getRegInfo().cpValue2Value(PhiCpRes, PN, mvec);
214 BB->insert(BB->begin(), mvec.begin(), mvec.end());
215 } // for each Phi Instr in BB
216 } // for all BBs in function
219 //-------------------------------------------------------------------------
220 // Thid method inserts a copy instruction to a predecessor BB as a result
221 // of phi elimination.
222 //-------------------------------------------------------------------------
225 InstructionSelection::InsertPhiElimInstructions(BasicBlock *BB,
226 const vector<MachineInstr*>& CpVec)
228 Instruction *TermInst = (Instruction*)BB->getTerminator();
229 MachineCodeForInstruction &MC4Term = MachineCodeForInstruction::get(TermInst);
230 MachineInstr *FirstMIOfTerm = MC4Term.front();
231 assert (FirstMIOfTerm && "No Machine Instrs for terminator");
233 MachineFunction &MF = MachineFunction::get(BB->getParent());
235 // FIXME: if PHI instructions existed in the machine code, this would be
237 MachineBasicBlock *MBB = 0;
238 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
239 if (I->getBasicBlock() == BB) {
244 // find the position of first machine instruction generated by the
245 // terminator of this BB
246 MachineBasicBlock::iterator MCIt =
247 std::find(MBB->begin(), MBB->end(), FirstMIOfTerm);
249 assert(MCIt != MBB->end() && "Start inst of terminator not found");
251 // insert the copy instructions just before the first machine instruction
252 // generated for the terminator
253 MBB->insert(MCIt, CpVec.begin(), CpVec.end());
257 //---------------------------------------------------------------------------
258 // Function SelectInstructionsForTree
260 // Recursively walk the tree to select instructions.
261 // Do this top-down so that child instructions can exploit decisions
262 // made at the child instructions.
264 // E.g., if br(setle(reg,const)) decides the constant is 0 and uses
265 // a branch-on-integer-register instruction, then the setle node
266 // can use that information to avoid generating the SUBcc instruction.
268 // Note that this cannot be done bottom-up because setle must do this
269 // only if it is a child of the branch (otherwise, the result of setle
270 // may be used by multiple instructions).
271 //---------------------------------------------------------------------------
274 InstructionSelection::SelectInstructionsForTree(InstrTreeNode* treeRoot,
277 // Get the rule that matches this node.
279 int ruleForNode = burm_rule(treeRoot->state, goalnt);
281 if (ruleForNode == 0) {
282 std::cerr << "Could not match instruction tree for instr selection\n";
286 // Get this rule's non-terminals and the corresponding child nodes (if any)
288 short *nts = burm_nts[ruleForNode];
290 // First, select instructions for the current node and rule.
291 // (If this is a list node, not an instruction, then skip this step).
292 // This function is specific to the target architecture.
294 if (treeRoot->opLabel != VRegListOp)
296 vector<MachineInstr*> minstrVec;
298 InstructionNode* instrNode = (InstructionNode*)treeRoot;
299 assert(instrNode->getNodeType() == InstrTreeNode::NTInstructionNode);
301 GetInstructionsByRule(instrNode, ruleForNode, nts, Target, minstrVec);
303 MachineCodeForInstruction &mvec =
304 MachineCodeForInstruction::get(instrNode->getInstruction());
305 mvec.insert(mvec.end(), minstrVec.begin(), minstrVec.end());
308 // Then, recursively compile the child nodes, if any.
311 { // i.e., there is at least one kid
312 InstrTreeNode* kids[2];
313 int currentRule = ruleForNode;
314 burm_kids(treeRoot, currentRule, kids);
316 // First skip over any chain rules so that we don't visit
317 // the current node again.
319 while (ThisIsAChainRule(currentRule))
321 currentRule = burm_rule(treeRoot->state, nts[0]);
322 nts = burm_nts[currentRule];
323 burm_kids(treeRoot, currentRule, kids);
326 // Now we have the first non-chain rule so we have found
327 // the actual child nodes. Recursively compile them.
329 for (unsigned i = 0; nts[i]; i++)
332 InstrTreeNode::InstrTreeNodeType nodeType = kids[i]->getNodeType();
333 if (nodeType == InstrTreeNode::NTVRegListNode ||
334 nodeType == InstrTreeNode::NTInstructionNode)
335 SelectInstructionsForTree(kids[i], nts[i]);
339 // Finally, do any postprocessing on this node after its children
340 // have been translated
342 if (treeRoot->opLabel != VRegListOp)
343 PostprocessMachineCodeForTree((InstructionNode*)treeRoot, ruleForNode, nts);
346 //---------------------------------------------------------------------------
347 // Function PostprocessMachineCodeForTree
349 // Apply any final cleanups to machine code for the root of a subtree
350 // after selection for all its children has been completed.
353 InstructionSelection::PostprocessMachineCodeForTree(InstructionNode* instrNode,
357 // Fix up any constant operands in the machine instructions to either
358 // use an immediate field or to load the constant into a register
359 // Walk backwards and use direct indexes to allow insertion before current
361 Instruction* vmInstr = instrNode->getInstruction();
362 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(vmInstr);
363 for (unsigned i = mvec.size(); i != 0; --i)
365 vector<MachineInstr*> loadConstVec =
366 FixConstantOperandsForInstr(vmInstr, mvec[i-1], Target);
368 mvec.insert(mvec.begin()+i-1, loadConstVec.begin(), loadConstVec.end());
374 //===----------------------------------------------------------------------===//
375 // createInstructionSelectionPass - Public entrypoint for instruction selection
376 // and this file as a whole...
378 Pass *createInstructionSelectionPass(TargetMachine &T) {
379 return new InstructionSelection(T);