2003-10-05 04:26:39 +00:00
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//===- PromoteMemoryToRegister.cpp - Convert allocas to registers ---------===//
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2002-02-12 17:16:22 +00:00
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//
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2003-10-05 04:26:39 +00:00
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// This file promote memory references to be register references. It promotes
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// alloca instructions which only have loads and stores as uses. An alloca is
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// transformed by using dominator frontiers to place PHI nodes, then traversing
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// the function in depth-first order to rewrite loads and stores as appropriate.
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// This is just the standard SSA construction algorithm.
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2002-02-12 17:16:22 +00:00
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//
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//===----------------------------------------------------------------------===//
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2003-02-22 23:57:48 +00:00
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#include "llvm/Transforms/Utils/PromoteMemToReg.h"
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2002-02-12 18:27:41 +00:00
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#include "llvm/Analysis/Dominators.h"
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2002-02-12 17:16:22 +00:00
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#include "llvm/iMemory.h"
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2002-04-09 18:37:46 +00:00
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#include "llvm/iPHINode.h"
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2002-04-07 20:49:59 +00:00
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#include "llvm/Function.h"
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2002-04-28 19:55:58 +00:00
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#include "llvm/Constant.h"
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2003-04-18 19:25:22 +00:00
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#include "llvm/Support/CFG.h"
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2003-04-10 19:41:13 +00:00
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#include "Support/StringExtras.h"
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2003-02-22 23:57:48 +00:00
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/// isAllocaPromotable - Return true if this alloca is legal for promotion.
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/// This is true if there are only loads and stores to the alloca...
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///
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2003-03-03 17:25:18 +00:00
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bool isAllocaPromotable(const AllocaInst *AI, const TargetData &TD) {
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// FIXME: If the memory unit is of pointer or integer type, we can permit
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// assignments to subsections of the memory unit.
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2003-02-22 23:57:48 +00:00
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// Only allow direct loads and stores...
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for (Value::use_const_iterator UI = AI->use_begin(), UE = AI->use_end();
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UI != UE; ++UI) // Loop over all of the uses of the alloca
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if (!isa<LoadInst>(*UI))
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if (const StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
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if (SI->getOperand(0) == AI)
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return false; // Don't allow a store of the AI, only INTO the AI.
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} else {
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return false; // Not a load or store?
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}
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return true;
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}
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2002-03-27 23:17:37 +00:00
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2002-03-27 23:28:40 +00:00
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namespace {
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2003-02-22 23:57:48 +00:00
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struct PromoteMem2Reg {
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2003-10-05 03:16:07 +00:00
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// Allocas - The alloca instructions being promoted
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const std::vector<AllocaInst*> &Allocas;
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2003-02-22 23:57:48 +00:00
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DominanceFrontier &DF;
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2003-03-03 17:25:18 +00:00
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const TargetData &TD;
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2002-10-01 22:38:41 +00:00
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2003-10-05 03:16:07 +00:00
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// AllocaLookup - Reverse mapping of Allocas
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std::map<AllocaInst*, unsigned> AllocaLookup;
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// VersionNumbers - Current version counters for each alloca
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std::vector<unsigned> VersionNumbers;
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2002-04-28 19:12:38 +00:00
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2003-10-05 01:52:53 +00:00
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// NewPhiNodes - The PhiNodes we're adding.
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std::map<BasicBlock*, std::vector<PHINode*> > NewPhiNodes;
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// Visited - The set of basic blocks the renamer has already visited.
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std::set<BasicBlock*> Visited;
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2002-03-27 23:17:37 +00:00
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2002-04-28 19:12:38 +00:00
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public:
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2003-03-03 17:25:18 +00:00
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PromoteMem2Reg(const std::vector<AllocaInst*> &A, DominanceFrontier &df,
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2003-10-05 01:52:53 +00:00
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const TargetData &td) : Allocas(A), DF(df), TD(td) {}
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2002-04-28 19:12:38 +00:00
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2003-02-22 23:57:48 +00:00
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void run();
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2002-04-28 19:12:38 +00:00
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private:
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2003-02-22 22:25:17 +00:00
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void RenamePass(BasicBlock *BB, BasicBlock *Pred,
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2003-10-05 01:52:53 +00:00
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std::vector<Value*> &IncVals);
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2002-04-28 19:12:38 +00:00
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bool QueuePhiNode(BasicBlock *BB, unsigned AllocaIdx);
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};
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2002-03-27 23:28:40 +00:00
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} // end of anonymous namespace
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2002-02-12 17:16:22 +00:00
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2003-02-22 23:57:48 +00:00
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void PromoteMem2Reg::run() {
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Function &F = *DF.getRoot()->getParent();
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2003-10-05 01:52:53 +00:00
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2003-04-10 19:41:13 +00:00
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VersionNumbers.resize(Allocas.size());
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2002-02-12 18:27:41 +00:00
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2003-10-05 03:16:07 +00:00
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for (unsigned i = 0; i != Allocas.size(); ++i) {
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AllocaInst *AI = Allocas[i];
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assert(isAllocaPromotable(AI, TD) &&
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2003-02-22 23:57:48 +00:00
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"Cannot promote non-promotable alloca!");
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assert(Allocas[i]->getParent()->getParent() == &F &&
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"All allocas should be in the same function, which is same as DF!");
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2003-10-05 02:37:36 +00:00
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// Calculate the set of write-locations for each alloca. This is analogous
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// to counting the number of 'redefinitions' of each variable.
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2003-10-05 03:39:10 +00:00
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std::vector<BasicBlock*> DefiningBlocks;
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2002-04-28 18:27:55 +00:00
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for (Value::use_iterator U =AI->use_begin(), E = AI->use_end(); U != E; ++U)
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2003-10-05 03:16:07 +00:00
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if (StoreInst *SI = dyn_cast<StoreInst>(cast<Instruction>(*U)))
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2002-04-28 18:27:55 +00:00
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// jot down the basic-block it came from
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2003-10-05 03:39:10 +00:00
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DefiningBlocks.push_back(SI->getParent());
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2003-10-05 03:16:07 +00:00
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AllocaLookup[Allocas[i]] = i;
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2003-10-05 02:37:36 +00:00
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2003-10-05 03:26:25 +00:00
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// PhiNodeBlocks - A list of blocks that phi nodes have been inserted for
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// this alloca.
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std::vector<BasicBlock*> PhiNodeBlocks;
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2003-10-05 02:37:36 +00:00
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// Compute the locations where PhiNodes need to be inserted. Look at the
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// dominance frontier of EACH basic-block we have a write in.
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//
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2003-10-05 03:39:10 +00:00
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while (!DefiningBlocks.empty()) {
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BasicBlock *BB = DefiningBlocks.back();
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DefiningBlocks.pop_back();
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2002-04-28 18:27:55 +00:00
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// Look up the DF for this write, add it to PhiNodes
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2003-10-05 03:39:10 +00:00
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DominanceFrontier::const_iterator it = DF.find(BB);
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2003-04-10 19:41:13 +00:00
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if (it != DF.end()) {
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const DominanceFrontier::DomSetType &S = it->second;
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for (DominanceFrontier::DomSetType::iterator P = S.begin(),PE = S.end();
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P != PE; ++P)
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2003-10-05 03:26:25 +00:00
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if (QueuePhiNode(*P, i))
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2003-10-05 03:39:10 +00:00
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DefiningBlocks.push_back(*P);
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2003-04-10 19:41:13 +00:00
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}
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2002-04-28 18:27:55 +00:00
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}
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}
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2002-04-28 18:39:46 +00:00
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// Set the incoming values for the basic block to be null values for all of
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// the alloca's. We do this in case there is a load of a value that has not
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// been stored yet. In this case, it will get this null value.
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//
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2003-02-22 22:25:17 +00:00
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std::vector<Value *> Values(Allocas.size());
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2002-04-28 18:39:46 +00:00
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for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
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2002-04-29 18:48:30 +00:00
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Values[i] = Constant::getNullValue(Allocas[i]->getAllocatedType());
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2002-04-28 18:39:46 +00:00
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2002-04-28 18:27:55 +00:00
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// Walks all basic blocks in the function performing the SSA rename algorithm
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// and inserting the phi nodes we marked as necessary
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//
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2003-10-05 01:52:53 +00:00
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RenamePass(F.begin(), 0, Values);
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2003-10-05 04:26:39 +00:00
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// The renamer uses the Visited set to avoid infinite loops. Clear it now.
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2003-10-05 01:52:53 +00:00
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Visited.clear();
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2002-04-28 18:27:55 +00:00
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2003-10-05 01:52:53 +00:00
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// Remove the allocas themselves from the function...
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for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
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Instruction *A = Allocas[i];
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2002-04-28 18:27:55 +00:00
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2003-10-05 01:52:53 +00:00
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// If there are any uses of the alloca instructions left, they must be in
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2003-04-10 19:41:13 +00:00
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// sections of dead code that were not processed on the dominance frontier.
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// Just delete the users now.
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//
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2003-10-05 01:52:53 +00:00
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if (!A->use_empty())
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A->replaceAllUsesWith(Constant::getNullValue(A->getType()));
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A->getParent()->getInstList().erase(A);
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2002-04-28 18:27:55 +00:00
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}
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2003-10-05 04:26:39 +00:00
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// At this point, the renamer has added entries to PHI nodes for all reachable
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// code. Unfortunately, there may be blocks which are not reachable, which
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// the renamer hasn't traversed. If this is the case, the PHI nodes may not
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// have incoming values for all predecessors. Loop over all PHI nodes we have
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// created, inserting null constants if they are missing any incoming values.
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//
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for (std::map<BasicBlock*, std::vector<PHINode *> >::iterator I =
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NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E; ++I) {
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std::vector<BasicBlock*> Preds(pred_begin(I->first), pred_end(I->first));
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std::vector<PHINode*> &PNs = I->second;
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assert(!PNs.empty() && "Empty PHI node list??");
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// Only do work here if there the PHI nodes are missing incoming values. We
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// know that all PHI nodes that were inserted in a block will have the same
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// number of incoming values, so we can just check any PHI node.
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PHINode *FirstPHI = PNs[0];
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if (Preds.size() != FirstPHI->getNumIncomingValues()) {
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// Ok, now we know that all of the PHI nodes are missing entries for some
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// basic blocks. Start by sorting the incoming predecessors for efficient
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// access.
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std::sort(Preds.begin(), Preds.end());
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// Now we loop through all BB's which have entries in FirstPHI and remove
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// them from the Preds list.
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for (unsigned i = 0, e = FirstPHI->getNumIncomingValues(); i != e; ++i) {
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// Do a log(n) search of teh Preds list for the entry we want.
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std::vector<BasicBlock*>::iterator EntIt =
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std::lower_bound(Preds.begin(), Preds.end(),
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FirstPHI->getIncomingBlock(i));
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assert(EntIt != Preds.end() && *EntIt == FirstPHI->getIncomingBlock(i)&&
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"PHI node has entry for a block which is not a predecessor!");
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// Remove the entry
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Preds.erase(EntIt);
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}
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// At this point, the blocks left in the preds list must have dummy
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// entries inserted into every PHI nodes for the block.
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for (unsigned i = 0, e = PNs.size(); i != e; ++i) {
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PHINode *PN = PNs[i];
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Value *NullVal = Constant::getNullValue(PN->getType());
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for (unsigned pred = 0, e = Preds.size(); pred != e; ++pred)
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PN->addIncoming(NullVal, Preds[pred]);
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}
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}
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}
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2002-04-28 18:27:55 +00:00
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}
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2002-03-27 23:17:37 +00:00
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2002-04-28 18:27:55 +00:00
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// QueuePhiNode - queues a phi-node to be added to a basic-block for a specific
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// Alloca returns true if there wasn't already a phi-node for that variable
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//
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2003-02-22 23:57:48 +00:00
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bool PromoteMem2Reg::QueuePhiNode(BasicBlock *BB, unsigned AllocaNo) {
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2002-04-28 18:27:55 +00:00
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// Look up the basic-block in question
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2003-02-22 22:25:17 +00:00
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std::vector<PHINode*> &BBPNs = NewPhiNodes[BB];
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2002-04-28 18:27:55 +00:00
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if (BBPNs.empty()) BBPNs.resize(Allocas.size());
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2002-03-27 23:17:37 +00:00
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2002-04-28 18:27:55 +00:00
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// If the BB already has a phi node added for the i'th alloca then we're done!
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2002-04-28 18:54:01 +00:00
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if (BBPNs[AllocaNo]) return false;
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2002-03-27 23:17:37 +00:00
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2002-09-10 22:38:47 +00:00
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// Create a PhiNode using the dereferenced type... and add the phi-node to the
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2003-04-18 19:25:22 +00:00
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// BasicBlock.
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2003-10-05 04:26:39 +00:00
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BBPNs[AllocaNo] = new PHINode(Allocas[AllocaNo]->getAllocatedType(),
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Allocas[AllocaNo]->getName() + "." +
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utostr(VersionNumbers[AllocaNo]++),
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BB->begin());
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2002-04-28 18:27:55 +00:00
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return true;
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}
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2002-03-27 23:17:37 +00:00
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2003-02-22 23:57:48 +00:00
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void PromoteMem2Reg::RenamePass(BasicBlock *BB, BasicBlock *Pred,
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2003-10-05 01:52:53 +00:00
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std::vector<Value*> &IncomingVals) {
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2003-10-05 03:45:44 +00:00
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2003-10-05 02:37:36 +00:00
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// If this BB needs a PHI node, update the PHI node for each variable we need
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// PHI nodes for.
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std::map<BasicBlock*, std::vector<PHINode *> >::iterator
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BBPNI = NewPhiNodes.find(BB);
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if (BBPNI != NewPhiNodes.end()) {
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std::vector<PHINode *> &BBPNs = BBPNI->second;
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for (unsigned k = 0; k != BBPNs.size(); ++k)
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if (PHINode *PN = BBPNs[k]) {
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2003-10-05 04:26:39 +00:00
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// Add this incoming value to the PHI node.
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PN->addIncoming(IncomingVals[k], Pred);
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// The currently active variable for this block is now the PHI.
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2003-10-05 02:37:36 +00:00
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IncomingVals[k] = PN;
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2003-04-25 00:54:58 +00:00
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}
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2003-10-05 02:37:36 +00:00
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}
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2002-03-27 23:17:37 +00:00
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2002-04-28 18:27:55 +00:00
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// don't revisit nodes
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2002-04-28 18:54:01 +00:00
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if (Visited.count(BB)) return;
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2002-04-28 18:27:55 +00:00
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// mark as visited
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2002-04-28 18:54:01 +00:00
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Visited.insert(BB);
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2002-03-27 23:17:37 +00:00
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2003-10-05 03:45:44 +00:00
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for (BasicBlock::iterator II = BB->begin(); !isa<TerminatorInst>(II); ) {
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2003-10-05 01:52:53 +00:00
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Instruction *I = II++; // get the instruction, increment iterator
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2002-03-27 23:17:37 +00:00
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2002-04-28 18:27:55 +00:00
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if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
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2003-02-22 22:25:17 +00:00
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if (AllocaInst *Src = dyn_cast<AllocaInst>(LI->getPointerOperand())) {
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2003-10-05 03:16:07 +00:00
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std::map<AllocaInst*, unsigned>::iterator AI = AllocaLookup.find(Src);
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2002-04-28 18:54:01 +00:00
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if (AI != AllocaLookup.end()) {
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Value *V = IncomingVals[AI->second];
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2002-03-27 23:17:37 +00:00
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2002-04-28 18:27:55 +00:00
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// walk the use list of this load and replace all uses with r
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LI->replaceAllUsesWith(V);
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2003-10-05 01:52:53 +00:00
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BB->getInstList().erase(LI);
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2002-04-28 18:27:55 +00:00
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}
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}
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} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
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2003-02-22 22:25:17 +00:00
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// Delete this instruction and mark the name as the current holder of the
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2002-04-28 18:27:55 +00:00
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// value
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2003-02-22 22:25:17 +00:00
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|
|
if (AllocaInst *Dest = dyn_cast<AllocaInst>(SI->getPointerOperand())) {
|
2003-10-05 03:16:07 +00:00
|
|
|
std::map<AllocaInst *, unsigned>::iterator ai = AllocaLookup.find(Dest);
|
2002-04-28 18:27:55 +00:00
|
|
|
if (ai != AllocaLookup.end()) {
|
|
|
|
// what value were we writing?
|
2002-04-28 18:54:01 +00:00
|
|
|
IncomingVals[ai->second] = SI->getOperand(0);
|
2003-10-05 01:52:53 +00:00
|
|
|
BB->getInstList().erase(SI);
|
2002-04-28 18:27:55 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
2003-10-05 03:45:44 +00:00
|
|
|
|
|
|
|
// Recurse to our successors
|
|
|
|
TerminatorInst *TI = BB->getTerminator();
|
|
|
|
for (unsigned i = 0; i != TI->getNumSuccessors(); i++) {
|
|
|
|
std::vector<Value*> OutgoingVals(IncomingVals);
|
|
|
|
RenamePass(TI->getSuccessor(i), BB, OutgoingVals);
|
|
|
|
}
|
2002-02-12 17:16:22 +00:00
|
|
|
}
|
2002-03-27 23:28:40 +00:00
|
|
|
|
2003-02-22 23:57:48 +00:00
|
|
|
/// PromoteMemToReg - Promote the specified list of alloca instructions into
|
|
|
|
/// scalar registers, inserting PHI nodes as appropriate. This function makes
|
|
|
|
/// use of DominanceFrontier information. This function does not modify the CFG
|
|
|
|
/// of the function at all. All allocas must be from the same function.
|
|
|
|
///
|
|
|
|
void PromoteMemToReg(const std::vector<AllocaInst*> &Allocas,
|
2003-03-03 17:25:18 +00:00
|
|
|
DominanceFrontier &DF, const TargetData &TD) {
|
2003-10-05 01:52:53 +00:00
|
|
|
// If there is nothing to do, bail out...
|
|
|
|
if (Allocas.empty()) return;
|
2003-03-03 17:25:18 +00:00
|
|
|
PromoteMem2Reg(Allocas, DF, TD).run();
|
2002-03-27 23:28:40 +00:00
|
|
|
}
|