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96b21c1054
computes a dependence graph for data dependences on memory locations using interprocedural Mod/Ref information. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4957 91177308-0d34-0410-b5e6-96231b3b80d8
493 lines
19 KiB
C++
493 lines
19 KiB
C++
//===- MemoryDepAnalysis.cpp - Compute dep graph for memory ops --*-C++-*--===//
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//
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// This file implements a pass (MemoryDepAnalysis) that computes memory-based
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// data dependences between instructions for each function in a module.
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// Memory-based dependences occur due to load and store operations, but
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// also the side-effects of call instructions.
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//
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// The result of this pass is a DependenceGraph for each function
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// representing the memory-based data dependences between instructions.
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/MemoryDepAnalysis.h"
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#include "llvm/Analysis/IPModRef.h"
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#include "llvm/Analysis/DataStructure.h"
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#include "llvm/Analysis/DSGraph.h"
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#include "llvm/Module.h"
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#include "llvm/Function.h"
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#include "llvm/iMemory.h"
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#include "llvm/iOther.h"
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#include "llvm/Support/InstVisitor.h"
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#include "llvm/Support/CFG.h"
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#include "Support/TarjanSCCIterator.h"
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#include "Support/Statistic.h"
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#include "Support/NonCopyable.h"
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#include "Support/STLExtras.h"
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#include "Support/hash_map"
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#include "Support/hash_set"
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#include <iostream>
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///--------------------------------------------------------------------------
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/// struct ModRefTable:
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///
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/// A data structure that tracks ModRefInfo for instructions:
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/// -- modRefMap is a map of Instruction* -> ModRefInfo for the instr.
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/// -- definers is a vector of instructions that define any node
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/// -- users is a vector of instructions that reference any node
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/// -- numUsersBeforeDef is a vector indicating that the number of users
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/// seen before definers[i] is numUsersBeforeDef[i].
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///
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/// numUsersBeforeDef[] effectively tells us the exact interleaving of
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/// definers and users within the ModRefTable.
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/// This is only maintained when constructing the table for one SCC, and
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/// not copied over from one table to another since it is no longer useful.
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///--------------------------------------------------------------------------
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struct ModRefTable
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{
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typedef hash_map<Instruction*, ModRefInfo> ModRefMap;
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typedef ModRefMap::const_iterator const_map_iterator;
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typedef ModRefMap:: iterator map_iterator;
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typedef std::vector<Instruction*>::const_iterator const_ref_iterator;
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typedef std::vector<Instruction*>:: iterator ref_iterator;
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ModRefMap modRefMap;
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std::vector<Instruction*> definers;
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std::vector<Instruction*> users;
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std::vector<unsigned> numUsersBeforeDef;
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// Iterators to enumerate all the defining instructions
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const_ref_iterator defsBegin() const { return definers.begin(); }
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ref_iterator defsBegin() { return definers.begin(); }
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const_ref_iterator defsEnd() const { return definers.end(); }
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ref_iterator defsEnd() { return definers.end(); }
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// Iterators to enumerate all the user instructions
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const_ref_iterator usersBegin() const { return users.begin(); }
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ref_iterator usersBegin() { return users.begin(); }
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const_ref_iterator usersEnd() const { return users.end(); }
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ref_iterator usersEnd() { return users.end(); }
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// Iterator identifying the last user that was seen *before* a
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// specified def. In particular, all users in the half-closed range
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// [ usersBegin(), usersBeforeDef_End(defPtr) )
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// were seen *before* the specified def. All users in the half-closed range
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// [ usersBeforeDef_End(defPtr), usersEnd() )
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// were seen *after* the specified def.
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//
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ref_iterator usersBeforeDef_End(const_ref_iterator defPtr) {
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unsigned defIndex = (unsigned) (defPtr - defsBegin());
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assert(defIndex < numUsersBeforeDef.size());
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assert(usersBegin() + numUsersBeforeDef[defIndex] <= usersEnd());
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return usersBegin() + numUsersBeforeDef[defIndex];
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}
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const_ref_iterator usersBeforeDef_End(const_ref_iterator defPtr) const {
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return const_cast<ModRefTable*>(this)->usersBeforeDef_End(defPtr);
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}
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//
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// Modifier methods
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//
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void AddDef(Instruction* D) {
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definers.push_back(D);
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numUsersBeforeDef.push_back(users.size());
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}
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void AddUse(Instruction* U) {
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users.push_back(U);
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}
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void Insert(const ModRefTable& fromTable) {
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modRefMap.insert(fromTable.modRefMap.begin(), fromTable.modRefMap.end());
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definers.insert(definers.end(),
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fromTable.definers.begin(), fromTable.definers.end());
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users.insert(users.end(),
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fromTable.users.begin(), fromTable.users.end());
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numUsersBeforeDef.clear(); /* fromTable.numUsersBeforeDef is ignored */
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}
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};
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///--------------------------------------------------------------------------
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/// class ModRefInfoBuilder:
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///
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/// A simple InstVisitor<> class that retrieves the Mod/Ref info for
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/// Load/Store/Call instructions and inserts this information in
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/// a ModRefTable. It also records all instructions that Mod any node
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/// and all that use any node.
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///--------------------------------------------------------------------------
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class ModRefInfoBuilder: public InstVisitor<ModRefInfoBuilder>,
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public NonCopyable
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{
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const DSGraph& funcGraph;
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const FunctionModRefInfo& funcModRef;
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ModRefTable& modRefTable;
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ModRefInfoBuilder(); // do not implement
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public:
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/*ctor*/ ModRefInfoBuilder(const DSGraph& _funcGraph,
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const FunctionModRefInfo& _funcModRef,
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ModRefTable& _modRefTable)
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: funcGraph(_funcGraph), funcModRef(_funcModRef), modRefTable(_modRefTable)
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{
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}
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// At a call instruction, retrieve the ModRefInfo using IPModRef results.
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// Add the call to the defs list if it modifies any nodes and to the uses
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// list if it refs any nodes.
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//
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void visitCallInst (CallInst& callInst) {
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ModRefInfo safeModRef(funcGraph.getGraphSize());
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const ModRefInfo* callModRef = funcModRef.getModRefInfo(callInst);
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if (callModRef == NULL)
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{ // call to external/unknown function: mark all nodes as Mod and Ref
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safeModRef.getModSet().set();
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safeModRef.getRefSet().set();
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callModRef = &safeModRef;
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}
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modRefTable.modRefMap.insert(std::make_pair(&callInst,
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ModRefInfo(*callModRef)));
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if (callModRef->getModSet().any())
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modRefTable.AddDef(&callInst);
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if (callModRef->getRefSet().any())
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modRefTable.AddUse(&callInst);
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}
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// At a store instruction, add to the mod set the single node pointed to
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// by the pointer argument of the store. Interestingly, if there is no
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// such node, that would be a null pointer reference!
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void visitStoreInst (StoreInst& storeInst) {
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const DSNodeHandle& ptrNode =
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funcGraph.getNodeForValue(storeInst.getPointerOperand());
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if (const DSNode* target = ptrNode.getNode())
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{
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unsigned nodeId = funcModRef.getNodeId(target);
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ModRefInfo& minfo =
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modRefTable.modRefMap.insert(
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std::make_pair(&storeInst,
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ModRefInfo(funcGraph.getGraphSize()))).first->second;
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minfo.setNodeIsMod(nodeId);
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modRefTable.AddDef(&storeInst);
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}
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else
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std::cerr << "Warning: Uninitialized pointer reference!\n";
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}
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// At a load instruction, add to the ref set the single node pointed to
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// by the pointer argument of the load. Interestingly, if there is no
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// such node, that would be a null pointer reference!
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void visitLoadInst (LoadInst& loadInst) {
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const DSNodeHandle& ptrNode =
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funcGraph.getNodeForValue(loadInst.getPointerOperand());
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if (const DSNode* target = ptrNode.getNode())
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{
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unsigned nodeId = funcModRef.getNodeId(target);
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ModRefInfo& minfo =
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modRefTable.modRefMap.insert(
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std::make_pair(&loadInst,
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ModRefInfo(funcGraph.getGraphSize()))).first->second;
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minfo.setNodeIsRef(nodeId);
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modRefTable.AddUse(&loadInst);
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}
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else
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std::cerr << "Warning: Uninitialized pointer reference!\n";
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}
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};
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//----------------------------------------------------------------------------
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// class MemoryDepAnalysis: A dep. graph for load/store/call instructions
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//----------------------------------------------------------------------------
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/// Basic dependence gathering algorithm, using TarjanSCCIterator on CFG:
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///
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/// for every SCC S in the CFG in PostOrder on the SCC DAG
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/// {
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/// for every basic block BB in S in *postorder*
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/// for every instruction I in BB in reverse
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/// Add (I, ModRef[I]) to ModRefCurrent
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/// if (Mod[I] != NULL)
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/// Add I to DefSetCurrent: { I \in S : Mod[I] != NULL }
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/// if (Ref[I] != NULL)
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/// Add I to UseSetCurrent: { I : Ref[I] != NULL }
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///
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/// for every def D in DefSetCurrent
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///
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/// // NOTE: D comes after itself iff S contains a loop
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/// if (HasLoop(S) && D & D)
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/// Add output-dep: D -> D2
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///
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/// for every def D2 *after* D in DefSetCurrent
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/// // NOTE: D2 comes before D in execution order
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/// if (D & D2)
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/// Add output-dep: D2 -> D
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/// if (HasLoop(S))
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/// Add output-dep: D -> D2
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///
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/// for every use U in UseSetCurrent that was seen *before* D
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/// // NOTE: U comes after D in execution order
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/// if (U & D)
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/// if (U != D || HasLoop(S))
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/// Add true-dep: D -> U
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/// if (HasLoop(S))
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/// Add anti-dep: U -> D
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///
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/// for every use U in UseSetCurrent that was seen *after* D
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/// // NOTE: U comes before D in execution order
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/// if (U & D)
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/// if (U != D || HasLoop(S))
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/// Add anti-dep: U -> D
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/// if (HasLoop(S))
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/// Add true-dep: D -> U
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///
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/// for every def Dnext in DefSetAfter
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/// // NOTE: Dnext comes after D in execution order
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/// if (Dnext & D)
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/// Add output-dep: D -> Dnext
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///
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/// for every use Unext in UseSetAfter
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/// // NOTE: Unext comes after D in execution order
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/// if (Unext & D)
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/// Add true-dep: D -> Unext
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///
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/// for every use U in UseSetCurrent
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/// for every def Dnext in DefSetAfter
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/// // NOTE: Dnext comes after U in execution order
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/// if (Dnext & D)
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/// Add anti-dep: U -> Dnext
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///
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/// Add ModRefCurrent to ModRefAfter: { (I, ModRef[I] ) }
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/// Add DefSetCurrent to DefSetAfter: { I : Mod[I] != NULL }
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/// Add UseSetCurrent to UseSetAfter: { I : Ref[I] != NULL }
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/// }
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///
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///
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void MemoryDepAnalysis::ProcessSCC(SCC<Function*>& S,
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ModRefTable& ModRefAfter)
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{
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ModRefTable ModRefCurrent;
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ModRefTable::ModRefMap& mapCurrent = ModRefCurrent.modRefMap;
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ModRefTable::ModRefMap& mapAfter = ModRefAfter.modRefMap;
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bool hasLoop = S.HasLoop();
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// Builder class fills out a ModRefTable one instruction at a time.
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// To use it, we just invoke it's visit function for each basic block:
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//
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// for each basic block BB in the SCC in *postorder*
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// for each instruction I in BB in *reverse*
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// ModRefInfoBuilder::visit(I)
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// : Add (I, ModRef[I]) to ModRefCurrent.modRefMap
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// : Add I to ModRefCurrent.definers if it defines any node
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// : Add I to ModRefCurrent.users if it uses any node
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//
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ModRefInfoBuilder builder(*funcGraph, *funcModRef, ModRefCurrent);
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for (SCC<Function*>::iterator BI=S.begin(), BE=S.end(); BI != BE; ++BI)
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// Note: BBs in the SCC<> created by TarjanSCCIterator are in postorder.
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for (BasicBlock::reverse_iterator II=(*BI)->rbegin(), IE=(*BI)->rend();
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II != IE; ++II)
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builder.visit(*II);
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/// for every def D in DefSetCurrent
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///
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for (ModRefTable::ref_iterator II=ModRefCurrent.defsBegin(),
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IE=ModRefCurrent.defsEnd(); II != IE; ++II)
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{
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/// // NOTE: D comes after itself iff S contains a loop
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/// if (HasLoop(S))
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/// Add output-dep: D -> D2
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if (hasLoop)
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funcDepGraph->AddSimpleDependence(**II, **II, OutputDependence);
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/// for every def D2 *after* D in DefSetCurrent
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/// // NOTE: D2 comes before D in execution order
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/// if (D2 & D)
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/// Add output-dep: D2 -> D
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/// if (HasLoop(S))
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/// Add output-dep: D -> D2
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for (ModRefTable::ref_iterator JI=II+1; JI != IE; ++JI)
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if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
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mapCurrent.find(*JI)->second.getModSet()))
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{
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funcDepGraph->AddSimpleDependence(**JI, **II, OutputDependence);
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if (hasLoop)
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funcDepGraph->AddSimpleDependence(**II, **JI, OutputDependence);
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}
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/// for every use U in UseSetCurrent that was seen *before* D
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/// // NOTE: U comes after D in execution order
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/// if (U & D)
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/// if (U != D || HasLoop(S))
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/// Add true-dep: U -> D
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/// if (HasLoop(S))
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/// Add anti-dep: D -> U
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ModRefTable::ref_iterator JI=ModRefCurrent.usersBegin();
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ModRefTable::ref_iterator JE = ModRefCurrent.usersBeforeDef_End(II);
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for ( ; JI != JE; ++JI)
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if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
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mapCurrent.find(*JI)->second.getRefSet()))
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{
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if (*II != *JI || hasLoop)
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funcDepGraph->AddSimpleDependence(**II, **JI, TrueDependence);
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if (hasLoop)
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funcDepGraph->AddSimpleDependence(**JI, **II, AntiDependence);
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}
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/// for every use U in UseSetCurrent that was seen *after* D
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/// // NOTE: U comes before D in execution order
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/// if (U & D)
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/// if (U != D || HasLoop(S))
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/// Add anti-dep: U -> D
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/// if (HasLoop(S))
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/// Add true-dep: D -> U
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for (/*continue JI*/ JE = ModRefCurrent.usersEnd(); JI != JE; ++JI)
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if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
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mapCurrent.find(*JI)->second.getRefSet()))
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{
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if (*II != *JI || hasLoop)
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funcDepGraph->AddSimpleDependence(**JI, **II, AntiDependence);
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if (hasLoop)
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funcDepGraph->AddSimpleDependence(**II, **JI, TrueDependence);
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}
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/// for every def Dnext in DefSetPrev
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/// // NOTE: Dnext comes after D in execution order
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/// if (Dnext & D)
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/// Add output-dep: D -> Dnext
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for (ModRefTable::ref_iterator JI=ModRefAfter.defsBegin(),
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JE=ModRefAfter.defsEnd(); JI != JE; ++JI)
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if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
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mapAfter.find(*JI)->second.getModSet()))
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funcDepGraph->AddSimpleDependence(**II, **JI, OutputDependence);
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/// for every use Unext in UseSetAfter
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/// // NOTE: Unext comes after D in execution order
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/// if (Unext & D)
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/// Add true-dep: D -> Unext
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for (ModRefTable::ref_iterator JI=ModRefAfter.usersBegin(),
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JE=ModRefAfter.usersEnd(); JI != JE; ++JI)
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if (!Disjoint(mapCurrent.find(*II)->second.getModSet(),
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mapAfter.find(*JI)->second.getRefSet()))
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funcDepGraph->AddSimpleDependence(**II, **JI, TrueDependence);
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}
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///
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/// for every use U in UseSetCurrent
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/// for every def Dnext in DefSetAfter
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/// // NOTE: Dnext comes after U in execution order
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/// if (Dnext & D)
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/// Add anti-dep: U -> Dnext
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for (ModRefTable::ref_iterator II=ModRefCurrent.usersBegin(),
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IE=ModRefCurrent.usersEnd(); II != IE; ++II)
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for (ModRefTable::ref_iterator JI=ModRefAfter.defsBegin(),
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JE=ModRefAfter.defsEnd(); JI != JE; ++JI)
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if (!Disjoint(mapCurrent.find(*II)->second.getRefSet(),
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mapAfter.find(*JI)->second.getModSet()))
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funcDepGraph->AddSimpleDependence(**II, **JI, AntiDependence);
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/// Add ModRefCurrent to ModRefAfter: { (I, ModRef[I] ) }
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/// Add DefSetCurrent to DefSetAfter: { I : Mod[I] != NULL }
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/// Add UseSetCurrent to UseSetAfter: { I : Ref[I] != NULL }
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ModRefAfter.Insert(ModRefCurrent);
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}
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/// Debugging support methods
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///
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void MemoryDepAnalysis::print(std::ostream &O) const
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{
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// TEMPORARY LOOP
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for (hash_map<Function*, DependenceGraph*>::const_iterator
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I = funcMap.begin(), E = funcMap.end(); I != E; ++I)
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{
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Function* func = I->first;
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DependenceGraph* depGraph = I->second;
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O << "\n================================================================\n";
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O << "DEPENDENCE GRAPH FOR MEMORY OPERATIONS IN FUNCTION " << func->getName();
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O << "\n================================================================\n\n";
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depGraph->print(*func, O);
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}
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}
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///
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/// Run the pass on a function
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///
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bool MemoryDepAnalysis::runOnFunction(Function& func)
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{
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assert(! func.isExternal());
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// Get the FunctionModRefInfo holding IPModRef results for this function.
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// Use the TD graph recorded within the FunctionModRefInfo object, which
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// may not be the same as the original TD graph computed by DS analysis.
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//
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funcModRef = &getAnalysis<IPModRef>().getFunctionModRefInfo(func);
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funcGraph = &funcModRef->getFuncGraph();
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// TEMPORARY: ptr to depGraph (later just becomes "this").
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assert(funcMap.find(&func) == funcMap.end() && "Analyzing function twice?");
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funcDepGraph = funcMap[&func] = new DependenceGraph();
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ModRefTable ModRefAfter;
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SCC<Function*>* nextSCC;
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for (TarjanSCC_iterator<Function*> tarjSCCiter = tarj_begin(&func);
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(nextSCC = *tarjSCCiter) != NULL; ++tarjSCCiter)
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ProcessSCC(*nextSCC, ModRefAfter);
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return true;
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}
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//-------------------------------------------------------------------------
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// TEMPORARY FUNCTIONS TO MAKE THIS A MODULE PASS ---
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// These functions will go away once this class becomes a FunctionPass.
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//
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// Driver function to compute dependence graphs for every function.
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// This is temporary and will go away once this is a FunctionPass.
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//
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bool MemoryDepAnalysis::run(Module& M)
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{
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for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI)
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if (! FI->isExternal())
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runOnFunction(*FI); // automatically inserts each depGraph into funcMap
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return true;
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}
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// Release all the dependence graphs in the map.
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|
void MemoryDepAnalysis::releaseMemory()
|
|
{
|
|
for (hash_map<Function*, DependenceGraph*>::const_iterator
|
|
I = funcMap.begin(), E = funcMap.end(); I != E; ++I)
|
|
delete I->second;
|
|
funcMap.clear();
|
|
|
|
// Clear pointers because the pass constructor will not be invoked again.
|
|
funcDepGraph = NULL;
|
|
funcGraph = NULL;
|
|
funcModRef = NULL;
|
|
}
|
|
|
|
MemoryDepAnalysis::~MemoryDepAnalysis()
|
|
{
|
|
releaseMemory();
|
|
}
|
|
|
|
//----END TEMPORARY FUNCTIONS----------------------------------------------
|
|
|
|
|
|
void MemoryDepAnalysis::dump() const
|
|
{
|
|
this->print(std::cerr);
|
|
}
|
|
|
|
static RegisterAnalysis<MemoryDepAnalysis>
|
|
Z("memdep", "Memory Dependence Analysis");
|
|
|