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/Function.h"
19 #include "llvm/IntrinsicLowering.h"
20 #include "llvm/iPHINode.h"
21 #include "llvm/iOther.h"
22 #include "llvm/Pass.h"
23 #include "llvm/CodeGen/InstrForest.h"
24 #include "llvm/CodeGen/MachineCodeForInstruction.h"
25 #include "llvm/CodeGen/MachineFunction.h"
26 #include "llvm/Target/TargetMachine.h"
27 #include "../SparcV9RegInfo.h"
28 #include "Support/CommandLine.h"
29 #include "Support/LeakDetector.h"
32 std::vector<MachineInstr*>
33 FixConstantOperandsForInstr(Instruction *I, MachineInstr *MI,
38 //===--------------------------------------------------------------------===//
39 // SelectDebugLevel - Allow command line control over debugging.
41 enum SelectDebugLevel_t {
43 Select_PrintMachineCode,
44 Select_DebugInstTrees,
45 Select_DebugBurgTrees,
48 // Enable Debug Options to be specified on the command line
49 cl::opt<SelectDebugLevel_t>
50 SelectDebugLevel("dselect", cl::Hidden,
51 cl::desc("enable instruction selection debug information"),
53 clEnumValN(Select_NoDebugInfo, "n", "disable debug output"),
54 clEnumValN(Select_PrintMachineCode, "y", "print generated machine code"),
55 clEnumValN(Select_DebugInstTrees, "i",
56 "print debugging info for instruction selection"),
57 clEnumValN(Select_DebugBurgTrees, "b", "print burg trees"),
61 //===--------------------------------------------------------------------===//
62 // InstructionSelection Pass
64 // This is the actual pass object that drives the instruction selection
67 class InstructionSelection : public FunctionPass {
68 TargetMachine &Target;
69 void InsertCodeForPhis(Function &F);
70 void InsertPhiElimInstructions(BasicBlock *BB,
71 const std::vector<MachineInstr*>& CpVec);
72 void SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt);
73 void PostprocessMachineCodeForTree(InstructionNode* instrNode,
74 int ruleForNode, short* nts);
76 InstructionSelection(TargetMachine &TM) : Target(TM) {}
78 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
82 bool runOnFunction(Function &F);
83 virtual const char *getPassName() const { return "Instruction Selection"; }
87 TmpInstruction::TmpInstruction(MachineCodeForInstruction& mcfi,
88 Value *s1, Value *s2, const std::string &name)
89 : Instruction(s1->getType(), Instruction::UserOp1, name)
93 Operands.push_back(Use(s1, this)); // s1 must be non-null
95 Operands.push_back(Use(s2, this));
97 // TmpInstructions should not be garbage checked.
98 LeakDetector::removeGarbageObject(this);
101 // Constructor that requires the type of the temporary to be specified.
102 // Both S1 and S2 may be NULL.(
103 TmpInstruction::TmpInstruction(MachineCodeForInstruction& mcfi,
104 const Type *Ty, Value *s1, Value* s2,
105 const std::string &name)
106 : Instruction(Ty, Instruction::UserOp1, name)
111 Operands.push_back(Use(s1, this));
113 Operands.push_back(Use(s2, this));
115 // TmpInstructions should not be garbage checked.
116 LeakDetector::removeGarbageObject(this);
119 bool InstructionSelection::runOnFunction(Function &F) {
120 // First pass - Walk the function, lowering any calls to intrinsic functions
121 // which the instruction selector cannot handle.
122 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
123 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; )
124 if (CallInst *CI = dyn_cast<CallInst>(I++))
125 if (Function *F = CI->getCalledFunction())
126 switch (F->getIntrinsicID()) {
127 case Intrinsic::not_intrinsic:
128 case Intrinsic::vastart:
129 case Intrinsic::vacopy:
130 case Intrinsic::vaend:
131 // We directly implement these intrinsics. Note that this knowledge
132 // is incestuously entangled with the code in
133 // SparcInstrSelection.cpp and must be updated when it is updated.
134 // Since ALL of the code in this library is incestuously intertwined
135 // with it already and sparc specific, we will live with this.
138 // All other intrinsic calls we must lower.
139 Instruction *Before = CI->getPrev();
140 Target.getIntrinsicLowering().LowerIntrinsicCall(CI);
141 if (Before) { // Move iterator to instruction after call
148 // Build the instruction trees to be given as inputs to BURG.
149 InstrForest instrForest(&F);
150 if (SelectDebugLevel >= Select_DebugInstTrees) {
151 std::cerr << "\n\n*** Input to instruction selection for function "
152 << F.getName() << "\n\n" << F
153 << "\n\n*** Instruction trees for function "
154 << F.getName() << "\n\n";
158 // Invoke BURG instruction selection for each tree
159 for (InstrForest::const_root_iterator RI = instrForest.roots_begin();
160 RI != instrForest.roots_end(); ++RI) {
161 InstructionNode* basicNode = *RI;
162 assert(basicNode->parent() == NULL && "A `root' node has a parent?");
164 // Invoke BURM to label each tree node with a state
165 burm_label(basicNode);
166 if (SelectDebugLevel >= Select_DebugBurgTrees) {
167 printcover(basicNode, 1, 0);
168 std::cerr << "\nCover cost == " << treecost(basicNode, 1, 0) <<"\n\n";
169 printMatches(basicNode);
172 // Then recursively walk the tree to select instructions
173 SelectInstructionsForTree(basicNode, /*goalnt*/1);
176 // Create the MachineBasicBlock records and add all of the MachineInstrs
177 // defined in the MachineCodeForInstruction objects to also live in the
178 // MachineBasicBlock objects.
179 MachineFunction &MF = MachineFunction::get(&F);
180 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
181 MachineBasicBlock *MCBB = new MachineBasicBlock(BI);
182 MF.getBasicBlockList().push_back(MCBB);
184 for (BasicBlock::iterator II = BI->begin(); II != BI->end(); ++II) {
185 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(II);
186 MCBB->insert(MCBB->end(), mvec.begin(), mvec.end());
190 // Insert phi elimination code
191 InsertCodeForPhis(F);
193 if (SelectDebugLevel >= Select_PrintMachineCode) {
194 std::cerr << "\n*** Machine instructions after INSTRUCTION SELECTION\n";
195 MachineFunction::get(&F).dump();
201 /// InsertCodeForPhis - This method inserts Phi elimination code for
202 /// all Phi nodes in the given function. After this method is called,
203 /// the Phi nodes still exist in the LLVM code, but copies are added to the
206 void InstructionSelection::InsertCodeForPhis(Function &F) {
207 // Iterate over every Phi node PN in F:
208 MachineFunction &MF = MachineFunction::get(&F);
209 for (MachineFunction::iterator BB = MF.begin(); BB != MF.end(); ++BB) {
210 for (BasicBlock::const_iterator IIt = BB->getBasicBlock()->begin();
211 const PHINode *PN = dyn_cast<PHINode>(IIt); ++IIt) {
212 // Create a new temporary register to hold the result of the Phi copy.
213 // The leak detector shouldn't track these nodes. They are not garbage,
214 // even though their parent field is never filled in.
215 Value *PhiCpRes = new PHINode(PN->getType(), PN->getName() + ":PhiCp");
216 LeakDetector::removeGarbageObject(PhiCpRes);
218 // For each of PN's incoming values, insert a copy in the corresponding
219 // predecessor block.
220 MachineCodeForInstruction &MCforPN = MachineCodeForInstruction::get (PN);
221 for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) {
222 std::vector<MachineInstr*> mvec, CpVec;
223 Target.getRegInfo()->cpValue2Value(PN->getIncomingValue(i),
225 for (std::vector<MachineInstr*>::iterator MI=mvec.begin();
226 MI != mvec.end(); ++MI) {
227 std::vector<MachineInstr*> CpVec2 =
228 FixConstantOperandsForInstr(const_cast<PHINode*>(PN), *MI, Target);
229 CpVec2.push_back(*MI);
230 CpVec.insert(CpVec.end(), CpVec2.begin(), CpVec2.end());
232 // Insert the copy instructions into the predecessor BB.
233 InsertPhiElimInstructions(PN->getIncomingBlock(i), CpVec);
234 MCforPN.insert (MCforPN.end (), CpVec.begin (), CpVec.end ());
236 // Insert a copy instruction from PhiCpRes to PN.
237 std::vector<MachineInstr*> mvec;
238 Target.getRegInfo()->cpValue2Value(PhiCpRes, const_cast<PHINode*>(PN),
240 BB->insert(BB->begin(), mvec.begin(), mvec.end());
241 MCforPN.insert (MCforPN.end (), mvec.begin (), mvec.end ());
242 } // for each Phi Instr in BB
243 } // for all BBs in function
246 /// InsertPhiElimInstructions - Inserts the instructions in CpVec into the
247 /// MachineBasicBlock corresponding to BB, just before its terminator
248 /// instruction. This is used by InsertCodeForPhis() to insert copies, above.
251 InstructionSelection::InsertPhiElimInstructions(BasicBlock *BB,
252 const std::vector<MachineInstr*>& CpVec)
254 Instruction *TermInst = (Instruction*)BB->getTerminator();
255 MachineCodeForInstruction &MC4Term = MachineCodeForInstruction::get(TermInst);
256 MachineInstr *FirstMIOfTerm = MC4Term.front();
257 assert (FirstMIOfTerm && "No Machine Instrs for terminator");
259 MachineBasicBlock *MBB = FirstMIOfTerm->getParent();
260 assert(MBB && "Machine BB for predecessor's terminator not found");
261 MachineBasicBlock::iterator MCIt = 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) {
308 std::vector<MachineInstr*> minstrVec;
310 InstructionNode* instrNode = (InstructionNode*)treeRoot;
311 assert(instrNode->getNodeType() == InstrTreeNode::NTInstructionNode);
313 GetInstructionsByRule(instrNode, ruleForNode, nts, Target, minstrVec);
315 MachineCodeForInstruction &mvec =
316 MachineCodeForInstruction::get(instrNode->getInstruction());
317 mvec.insert(mvec.end(), minstrVec.begin(), minstrVec.end());
320 // Then, recursively compile the child nodes, if any.
323 // i.e., there is at least one kid
324 InstrTreeNode* kids[2];
325 int currentRule = ruleForNode;
326 burm_kids(treeRoot, currentRule, kids);
328 // First skip over any chain rules so that we don't visit
329 // the current node again.
331 while (ThisIsAChainRule(currentRule)) {
332 currentRule = burm_rule(treeRoot->state, nts[0]);
333 nts = burm_nts[currentRule];
334 burm_kids(treeRoot, currentRule, kids);
337 // Now we have the first non-chain rule so we have found
338 // the actual child nodes. Recursively compile them.
340 for (unsigned i = 0; nts[i]; i++) {
342 InstrTreeNode::InstrTreeNodeType nodeType = kids[i]->getNodeType();
343 if (nodeType == InstrTreeNode::NTVRegListNode ||
344 nodeType == InstrTreeNode::NTInstructionNode)
345 SelectInstructionsForTree(kids[i], nts[i]);
349 // Finally, do any post-processing on this node after its children
350 // have been translated
352 if (treeRoot->opLabel != VRegListOp)
353 PostprocessMachineCodeForTree((InstructionNode*)treeRoot, ruleForNode, nts);
356 //---------------------------------------------------------------------------
357 // Function PostprocessMachineCodeForTree
359 // Apply any final cleanups to machine code for the root of a subtree
360 // after selection for all its children has been completed.
363 InstructionSelection::PostprocessMachineCodeForTree(InstructionNode* instrNode,
367 // Fix up any constant operands in the machine instructions to either
368 // use an immediate field or to load the constant into a register
369 // Walk backwards and use direct indexes to allow insertion before current
371 Instruction* vmInstr = instrNode->getInstruction();
372 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(vmInstr);
373 for (unsigned i = mvec.size(); i != 0; --i) {
374 std::vector<MachineInstr*> loadConstVec =
375 FixConstantOperandsForInstr(vmInstr, mvec[i-1], Target);
377 mvec.insert(mvec.begin()+i-1, loadConstVec.begin(), loadConstVec.end());
382 //===----------------------------------------------------------------------===//
383 // createInstructionSelectionPass - Public entrypoint for instruction selection
384 // and this file as a whole...
386 FunctionPass *llvm::createInstructionSelectionPass(TargetMachine &TM) {
387 return new InstructionSelection(TM);