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c0b9dc5be7
ilist of MachineInstr objects. This allows constant time removal and insertion of MachineInstr instances from anywhere in each MachineBasicBlock. It also allows for constant time splicing of MachineInstrs into or out of MachineBasicBlocks. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11340 91177308-0d34-0410-b5e6-96231b3b80d8
323 lines
13 KiB
C++
323 lines
13 KiB
C++
//===-- FunctionLiveVarInfo.cpp - Live Variable Analysis for a Function ---===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This is the interface to function level live variable information that is
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// provided by live variable analysis.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/FunctionLiveVarInfo.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Support/CFG.h"
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#include "Support/PostOrderIterator.h"
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#include "Support/SetOperations.h"
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#include "Support/CommandLine.h"
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#include "BBLiveVar.h"
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namespace llvm {
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static RegisterAnalysis<FunctionLiveVarInfo>
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X("livevar", "Live Variable Analysis");
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LiveVarDebugLevel_t DEBUG_LV;
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static cl::opt<LiveVarDebugLevel_t, true>
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DEBUG_LV_opt("dlivevar", cl::Hidden, cl::location(DEBUG_LV),
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cl::desc("enable live-variable debugging information"),
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cl::values(
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clEnumValN(LV_DEBUG_None , "n", "disable debug output"),
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clEnumValN(LV_DEBUG_Normal , "y", "enable debug output"),
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clEnumValN(LV_DEBUG_Instr, "i", "print live-var sets before/after "
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"every machine instrn"),
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clEnumValN(LV_DEBUG_Verbose, "v", "print def, use sets for every instrn also"),
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0));
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//-----------------------------------------------------------------------------
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// Accessor Functions
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//-----------------------------------------------------------------------------
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// gets OutSet of a BB
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const ValueSet &FunctionLiveVarInfo::getOutSetOfBB(const BasicBlock *BB) const {
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return BBLiveVarInfo.find(BB)->second->getOutSet();
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}
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ValueSet &FunctionLiveVarInfo::getOutSetOfBB(const BasicBlock *BB) {
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return BBLiveVarInfo[BB]->getOutSet();
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}
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// gets InSet of a BB
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const ValueSet &FunctionLiveVarInfo::getInSetOfBB(const BasicBlock *BB) const {
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return BBLiveVarInfo.find(BB)->second->getInSet();
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}
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ValueSet &FunctionLiveVarInfo::getInSetOfBB(const BasicBlock *BB) {
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return BBLiveVarInfo[BB]->getInSet();
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}
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//-----------------------------------------------------------------------------
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// Performs live var analysis for a function
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//-----------------------------------------------------------------------------
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bool FunctionLiveVarInfo::runOnFunction(Function &F) {
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M = &F;
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if (DEBUG_LV) std::cerr << "Analysing live variables ...\n";
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// create and initialize all the BBLiveVars of the CFG
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constructBBs(M);
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unsigned int iter=0;
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while (doSingleBackwardPass(M, iter++))
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; // Iterate until we are done.
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if (DEBUG_LV) std::cerr << "Live Variable Analysis complete!\n";
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return false;
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}
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//-----------------------------------------------------------------------------
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// constructs BBLiveVars and init Def and In sets
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//-----------------------------------------------------------------------------
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void FunctionLiveVarInfo::constructBBs(const Function *F) {
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unsigned POId = 0; // Reverse Depth-first Order ID
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std::map<const BasicBlock*, unsigned> PONumbering;
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for (po_iterator<const Function*> BBI = po_begin(M), BBE = po_end(M);
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BBI != BBE; ++BBI)
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PONumbering[*BBI] = POId++;
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MachineFunction &MF = MachineFunction::get(F);
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for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
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const BasicBlock &BB = *I->getBasicBlock(); // get the current BB
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if (DEBUG_LV) std::cerr << " For BB " << RAV(BB) << ":\n";
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BBLiveVar *LVBB;
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std::map<const BasicBlock*, unsigned>::iterator POI = PONumbering.find(&BB);
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if (POI != PONumbering.end()) {
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// create a new BBLiveVar
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LVBB = new BBLiveVar(BB, *I, POId);
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} else {
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// The PO iterator does not discover unreachable blocks, but the random
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// iterator later may access these blocks. We must make sure to
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// initialize unreachable blocks as well. However, LV info is not correct
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// for those blocks (they are not analyzed)
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//
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LVBB = new BBLiveVar(BB, *I, ++POId);
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}
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BBLiveVarInfo[&BB] = LVBB;
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if (DEBUG_LV)
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LVBB->printAllSets();
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}
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}
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//-----------------------------------------------------------------------------
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// do one backward pass over the CFG (for iterative analysis)
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//-----------------------------------------------------------------------------
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bool FunctionLiveVarInfo::doSingleBackwardPass(const Function *M,
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unsigned iter) {
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if (DEBUG_LV) std::cerr << "\n After Backward Pass " << iter << "...\n";
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bool NeedAnotherIteration = false;
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for (po_iterator<const Function*> BBI = po_begin(M), BBE = po_end(M);
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BBI != BBE; ++BBI) {
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BBLiveVar *LVBB = BBLiveVarInfo[*BBI];
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assert(LVBB && "BasicBlock information not set for block!");
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if (DEBUG_LV) std::cerr << " For BB " << (*BBI)->getName() << ":\n";
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// InSets are initialized to "GenSet". Recompute only if OutSet changed.
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if(LVBB->isOutSetChanged())
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LVBB->applyTransferFunc(); // apply the Tran Func to calc InSet
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// OutSets are initialized to EMPTY. Recompute on first iter or if InSet
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// changed.
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if (iter == 0 || LVBB->isInSetChanged()) // to calc Outsets of preds
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NeedAnotherIteration |= LVBB->applyFlowFunc(BBLiveVarInfo);
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if (DEBUG_LV) LVBB->printInOutSets();
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}
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// true if we need to reiterate over the CFG
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return NeedAnotherIteration;
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}
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void FunctionLiveVarInfo::releaseMemory() {
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// First remove all BBLiveVars created in constructBBs().
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if (M) {
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for (Function::const_iterator I = M->begin(), E = M->end(); I != E; ++I)
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delete BBLiveVarInfo[I];
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BBLiveVarInfo.clear();
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}
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M = 0;
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// Then delete all objects of type ValueSet created in calcLiveVarSetsForBB
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// and entered into MInst2LVSetBI and MInst2LVSetAI (these are caches
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// to return ValueSet's before/after a machine instruction quickly).
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// We do not need to free up ValueSets in MInst2LVSetAI because it holds
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// pointers to the same sets as in MInst2LVSetBI (for all instructions
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// except the last one in a BB) or in BBLiveVar (for the last instruction).
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//
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for (hash_map<const MachineInstr*, ValueSet*>::iterator
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MI = MInst2LVSetBI.begin(),
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ME = MInst2LVSetBI.end(); MI != ME; ++MI)
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delete MI->second; // delete all ValueSets in MInst2LVSetBI
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MInst2LVSetBI.clear();
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MInst2LVSetAI.clear();
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}
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//-----------------------------------------------------------------------------
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// Following functions will give the LiveVar info for any machine instr in
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// a function. It should be called after a call to analyze().
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//
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// These functions calculate live var info for all the machine instrs in a
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// BB when LVInfo for one inst is requested. Hence, this function is useful
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// when live var info is required for many (or all) instructions in a basic
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// block. Also, the arguments to this function does not require specific
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// iterators.
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//-----------------------------------------------------------------------------
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//-----------------------------------------------------------------------------
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// Gives live variable information before a machine instruction
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//-----------------------------------------------------------------------------
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const ValueSet &
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FunctionLiveVarInfo::getLiveVarSetBeforeMInst(const MachineInstr *MI,
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const BasicBlock *BB) {
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ValueSet* &LVSet = MInst2LVSetBI[MI]; // ref. to map entry
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if (LVSet == NULL && BB != NULL) { // if not found and BB provided
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calcLiveVarSetsForBB(BB); // calc LVSet for all instrs in BB
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assert(LVSet != NULL);
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}
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return *LVSet;
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}
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//-----------------------------------------------------------------------------
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// Gives live variable information after a machine instruction
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//-----------------------------------------------------------------------------
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const ValueSet &
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FunctionLiveVarInfo::getLiveVarSetAfterMInst(const MachineInstr *MI,
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const BasicBlock *BB) {
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ValueSet* &LVSet = MInst2LVSetAI[MI]; // ref. to map entry
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if (LVSet == NULL && BB != NULL) { // if not found and BB provided
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calcLiveVarSetsForBB(BB); // calc LVSet for all instrs in BB
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assert(LVSet != NULL);
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}
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return *LVSet;
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}
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// This function applies a machine instr to a live var set (accepts OutSet) and
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// makes necessary changes to it (produces InSet). Note that two for loops are
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// used to first kill all defs and then to add all uses. This is because there
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// can be instructions like Val = Val + 1 since we allow multiple defs to a
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// machine instruction operand.
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//
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static void applyTranferFuncForMInst(ValueSet &LVS, const MachineInstr *MInst) {
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for (MachineInstr::const_val_op_iterator OpI = MInst->begin(),
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OpE = MInst->end(); OpI != OpE; ++OpI) {
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if (OpI.isDef()) // kill if this operand is a def
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LVS.erase(*OpI); // this definition kills any uses
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}
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// do for implicit operands as well
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for (unsigned i=0; i < MInst->getNumImplicitRefs(); ++i) {
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if (MInst->getImplicitOp(i).isDef())
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LVS.erase(MInst->getImplicitRef(i));
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}
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for (MachineInstr::const_val_op_iterator OpI = MInst->begin(),
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OpE = MInst->end(); OpI != OpE; ++OpI) {
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if (!isa<BasicBlock>(*OpI)) // don't process labels
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// add only if this operand is a use
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if (OpI.isUse())
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LVS.insert(*OpI); // An operand is a use - so add to use set
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}
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// do for implicit operands as well
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for (unsigned i = 0, e = MInst->getNumImplicitRefs(); i != e; ++i)
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if (MInst->getImplicitOp(i).isUse())
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LVS.insert(MInst->getImplicitRef(i));
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}
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//-----------------------------------------------------------------------------
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// This method calculates the live variable information for all the
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// instructions in a basic block and enter the newly constructed live
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// variable sets into a the caches (MInst2LVSetAI, MInst2LVSetBI)
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//-----------------------------------------------------------------------------
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void FunctionLiveVarInfo::calcLiveVarSetsForBB(const BasicBlock *BB) {
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BBLiveVar *BBLV = BBLiveVarInfo[BB];
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assert(BBLV && "BBLiveVar annotation doesn't exist?");
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const MachineBasicBlock &MIVec = BBLV->getMachineBasicBlock();
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const MachineFunction &MF = MachineFunction::get(M);
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const TargetMachine &TM = MF.getTarget();
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if (DEBUG_LV >= LV_DEBUG_Instr)
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std::cerr << "\n======For BB " << BB->getName()
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<< ": Live var sets for instructions======\n";
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ValueSet *SetAI = &getOutSetOfBB(BB); // init SetAI with OutSet
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ValueSet CurSet(*SetAI); // CurSet now contains OutSet
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// iterate over all the machine instructions in BB
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for (MachineBasicBlock::const_reverse_iterator MII = MIVec.rbegin(),
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MIE = MIVec.rend(); MII != MIE; ++MII) {
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// MI is cur machine inst
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const MachineInstr *MI = &*MII;
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MInst2LVSetAI[MI] = SetAI; // record in After Inst map
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applyTranferFuncForMInst(CurSet, MI); // apply the transfer Func
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ValueSet *NewSet = new ValueSet(CurSet); // create a new set with a copy
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// of the set after T/F
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MInst2LVSetBI[MI] = NewSet; // record in Before Inst map
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// If the current machine instruction has delay slots, mark values
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// used by this instruction as live before and after each delay slot
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// instruction (After(MI) is the same as Before(MI+1) except for last MI).
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if (unsigned DS = TM.getInstrInfo().getNumDelaySlots(MI->getOpcode())) {
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MachineBasicBlock::const_iterator fwdMII = MII.base(); // ptr to *next* MI
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for (unsigned i = 0; i < DS; ++i, ++fwdMII) {
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assert(fwdMII != MIVec.end() && "Missing instruction in delay slot?");
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const MachineInstr* DelaySlotMI = fwdMII;
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if (! TM.getInstrInfo().isNop(DelaySlotMI->getOpcode())) {
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set_union(*MInst2LVSetBI[DelaySlotMI], *NewSet);
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if (i+1 == DS)
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set_union(*MInst2LVSetAI[DelaySlotMI], *NewSet);
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}
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}
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}
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if (DEBUG_LV >= LV_DEBUG_Instr) {
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std::cerr << "\nLive var sets before/after instruction " << *MI;
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std::cerr << " Before: "; printSet(*NewSet); std::cerr << "\n";
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std::cerr << " After : "; printSet(*SetAI); std::cerr << "\n";
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}
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// SetAI will be used in the next iteration
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SetAI = NewSet;
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}
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}
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} // End llvm namespace
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