2 //***************************************************************************
7 // Machine-independent driver file for instruction selection.
8 // This file constructs a forest of BURG instruction trees and then
9 // uses the BURG-generated tree grammar (BURM) to find the optimal
10 // instruction sequences for a given machine.
13 // 7/02/01 - Vikram Adve - Created
14 //**************************************************************************/
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/MachineCodeForMethod.h"
22 #include "llvm/Target/MachineRegInfo.h"
23 #include "llvm/Target/TargetMachine.h"
24 #include "llvm/BasicBlock.h"
25 #include "llvm/Function.h"
26 #include "llvm/iPHINode.h"
27 #include "Support/CommandLine.h"
32 //******************** Internal Data Declarations ************************/
35 enum SelectDebugLevel_t {
37 Select_PrintMachineCode,
38 Select_DebugInstTrees,
39 Select_DebugBurgTrees,
42 // Enable Debug Options to be specified on the command line
43 cl::Enum<enum SelectDebugLevel_t> SelectDebugLevel("dselect", cl::Hidden,
44 "enable instruction selection debugging information",
45 clEnumValN(Select_NoDebugInfo, "n", "disable debug output"),
46 clEnumValN(Select_PrintMachineCode, "y", "print generated machine code"),
47 clEnumValN(Select_DebugInstTrees, "i", "print debugging info for instruction selection "),
48 clEnumValN(Select_DebugBurgTrees, "b", "print burg trees"), 0);
51 //******************** Forward Function Declarations ***********************/
54 static bool SelectInstructionsForTree (InstrTreeNode* treeRoot,
56 TargetMachine &target);
58 static void PostprocessMachineCodeForTree(InstructionNode* instrNode,
61 TargetMachine &target);
63 static void InsertCode4AllPhisInMeth(Function *F, TargetMachine &target);
67 //******************* Externally Visible Functions *************************/
70 //---------------------------------------------------------------------------
71 // Entry point for instruction selection using BURG.
72 // Returns true if instruction selection failed, false otherwise.
73 //---------------------------------------------------------------------------
76 SelectInstructionsForMethod(Function *F, TargetMachine &target)
81 // Build the instruction trees to be given as inputs to BURG.
83 InstrForest instrForest(F);
85 if (SelectDebugLevel >= Select_DebugInstTrees)
87 cerr << "\n\n*** Input to instruction selection for function "
88 << F->getName() << "\n\n";
91 cerr << "\n\n*** Instruction trees for function "
92 << F->getName() << "\n\n";
97 // Invoke BURG instruction selection for each tree
99 for (InstrForest::const_root_iterator RI = instrForest.roots_begin();
100 RI != instrForest.roots_end(); ++RI)
102 InstructionNode* basicNode = *RI;
103 assert(basicNode->parent() == NULL && "A `root' node has a parent?");
105 // Invoke BURM to label each tree node with a state
106 burm_label(basicNode);
108 if (SelectDebugLevel >= Select_DebugBurgTrees)
110 printcover(basicNode, 1, 0);
111 cerr << "\nCover cost == " << treecost(basicNode, 1, 0) << "\n\n";
112 printMatches(basicNode);
115 // Then recursively walk the tree to select instructions
116 if (SelectInstructionsForTree(basicNode, /*goalnt*/1, target))
124 // Record instructions in the vector for each basic block
126 for (Function::iterator BI = F->begin(), BE = F->end(); BI != BE; ++BI)
127 for (BasicBlock::iterator II = BI->begin(); II != BI->end(); ++II) {
128 MachineCodeForInstruction &mvec =MachineCodeForInstruction::get(II);
129 for (unsigned i=0; i < mvec.size(); i++)
130 BI->getMachineInstrVec().push_back(mvec[i]);
133 // Insert phi elimination code -- added by Ruchira
134 InsertCode4AllPhisInMeth(F, target);
137 if (SelectDebugLevel >= Select_PrintMachineCode)
139 cerr << "\n*** Machine instructions after INSTRUCTION SELECTION\n";
140 MachineCodeForMethod::get(F).dump();
147 //*********************** Private Functions *****************************/
150 //-------------------------------------------------------------------------
151 // Thid method inserts a copy instruction to a predecessor BB as a result
152 // of phi elimination.
153 //-------------------------------------------------------------------------
156 InsertPhiElimInstructions(BasicBlock *BB, const std::vector<MachineInstr*>& CpVec)
158 Instruction *TermInst = (Instruction*)BB->getTerminator();
159 MachineCodeForInstruction &MC4Term =MachineCodeForInstruction::get(TermInst);
160 MachineInstr *FirstMIOfTerm = *( MC4Term.begin() );
162 assert( FirstMIOfTerm && "No Machine Instrs for terminator" );
164 // get an iterator to machine instructions in the BB
165 MachineCodeForBasicBlock& bbMvec = BB->getMachineInstrVec();
166 MachineCodeForBasicBlock::iterator MCIt = bbMvec.begin();
168 // find the position of first machine instruction generated by the
169 // terminator of this BB
170 for( ; (MCIt != bbMvec.end()) && (*MCIt != FirstMIOfTerm) ; ++MCIt )
172 assert( MCIt != bbMvec.end() && "Start inst of terminator not found");
174 // insert the copy instructions just before the first machine instruction
175 // generated for the terminator
176 bbMvec.insert(MCIt, CpVec.begin(), CpVec.end());
178 //cerr << "\nPhiElimination copy inst: " << *CopyInstVec[0];
182 //-------------------------------------------------------------------------
183 // This method inserts phi elimination code for all BBs in a method
184 //-------------------------------------------------------------------------
187 InsertCode4AllPhisInMeth(Function *F, TargetMachine &target)
189 // for all basic blocks in function
191 for (Function::iterator BB = F->begin(); BB != F->end(); ++BB) {
192 BasicBlock::InstListType &InstList = BB->getInstList();
193 for (BasicBlock::iterator IIt = InstList.begin();
194 PHINode *PN = dyn_cast<PHINode>(&*IIt); ++IIt) {
195 // FIXME: This is probably wrong...
196 Value *PhiCpRes = new PHINode(PN->getType(), "PhiCp:");
198 // for each incoming value of the phi, insert phi elimination
200 for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) {
201 // insert the copy instruction to the predecessor BB
202 vector<MachineInstr*> mvec, CpVec;
203 target.getRegInfo().cpValue2Value(PN->getIncomingValue(i), PhiCpRes,
205 for (vector<MachineInstr*>::iterator MI=mvec.begin();
206 MI != mvec.end(); ++MI) {
207 vector<MachineInstr*> CpVec2 =
208 FixConstantOperandsForInstr(PN, *MI, target);
209 CpVec2.push_back(*MI);
210 CpVec.insert(CpVec.end(), CpVec2.begin(), CpVec2.end());
213 InsertPhiElimInstructions(PN->getIncomingBlock(i), CpVec);
216 vector<MachineInstr*> mvec;
217 target.getRegInfo().cpValue2Value(PhiCpRes, PN, mvec);
219 // get an iterator to machine instructions in the BB
220 MachineCodeForBasicBlock& bbMvec = BB->getMachineInstrVec();
222 bbMvec.insert(bbMvec.begin(), mvec.begin(), mvec.end());
223 } // for each Phi Instr in BB
224 } // for all BBs in function
228 //---------------------------------------------------------------------------
229 // Function PostprocessMachineCodeForTree
231 // Apply any final cleanups to machine code for the root of a subtree
232 // after selection for all its children has been completed.
233 //---------------------------------------------------------------------------
236 PostprocessMachineCodeForTree(InstructionNode* instrNode,
239 TargetMachine &target)
241 // Fix up any constant operands in the machine instructions to either
242 // use an immediate field or to load the constant into a register
243 // Walk backwards and use direct indexes to allow insertion before current
245 Instruction* vmInstr = instrNode->getInstruction();
246 MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(vmInstr);
247 for (int i = (int) mvec.size()-1; i >= 0; i--)
249 std::vector<MachineInstr*> loadConstVec =
250 FixConstantOperandsForInstr(vmInstr, mvec[i], target);
252 if (loadConstVec.size() > 0)
253 mvec.insert(mvec.begin()+i, loadConstVec.begin(), loadConstVec.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 SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt,
275 TargetMachine &target)
277 // Get the rule that matches this node.
279 int ruleForNode = burm_rule(treeRoot->state, goalnt);
281 if (ruleForNode == 0)
283 cerr << "Could not match instruction tree for instr selection\n";
288 // Get this rule's non-terminals and the corresponding child nodes (if any)
290 short *nts = burm_nts[ruleForNode];
292 // First, select instructions for the current node and rule.
293 // (If this is a list node, not an instruction, then skip this step).
294 // This function is specific to the target architecture.
296 if (treeRoot->opLabel != VRegListOp)
298 std::vector<MachineInstr*> minstrVec;
300 InstructionNode* instrNode = (InstructionNode*)treeRoot;
301 assert(instrNode->getNodeType() == InstrTreeNode::NTInstructionNode);
303 GetInstructionsByRule(instrNode, ruleForNode, nts, target, minstrVec);
305 MachineCodeForInstruction &mvec =
306 MachineCodeForInstruction::get(instrNode->getInstruction());
307 mvec.insert(mvec.end(), minstrVec.begin(), minstrVec.end());
310 // Then, recursively compile the child nodes, if any.
313 { // i.e., there is at least one kid
314 InstrTreeNode* kids[2];
315 int currentRule = ruleForNode;
316 burm_kids(treeRoot, currentRule, kids);
318 // First skip over any chain rules so that we don't visit
319 // the current node again.
321 while (ThisIsAChainRule(currentRule))
323 currentRule = burm_rule(treeRoot->state, nts[0]);
324 nts = burm_nts[currentRule];
325 burm_kids(treeRoot, currentRule, kids);
328 // Now we have the first non-chain rule so we have found
329 // the actual child nodes. Recursively compile them.
331 for (int i = 0; nts[i]; i++)
334 InstrTreeNode::InstrTreeNodeType nodeType = kids[i]->getNodeType();
335 if (nodeType == InstrTreeNode::NTVRegListNode ||
336 nodeType == InstrTreeNode::NTInstructionNode)
338 if (SelectInstructionsForTree(kids[i], nts[i], target))
339 return true; // failure
344 // Finally, do any postprocessing on this node after its children
345 // have been translated
347 if (treeRoot->opLabel != VRegListOp)
349 InstructionNode* instrNode = (InstructionNode*)treeRoot;
350 PostprocessMachineCodeForTree(instrNode, ruleForNode, nts, target);
353 return false; // success