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Integrate functionality of the mem2reg pass directly into this pass to make
the combination more effective git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8471 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -3,29 +3,43 @@
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// This transformation implements the well known scalar replacement of
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// aggregates transformation. This xform breaks up alloca instructions of
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// aggregate type (structure or array) into individual alloca instructions for
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// each member (if possible).
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// each member (if possible). Then, if possible, it transforms the individual
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// alloca instructions into nice clean scalar SSA form.
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//
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// This combines a simple SRoA algorithm with the Mem2Reg algorithm because
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// often interact, especially for C++ programs. As such, iterating between
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// SRoA, then Mem2Reg until we run out of things to promote works well.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/Pass.h"
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#include "llvm/iMemory.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Constants.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Transforms/Utils/PromoteMemToReg.h"
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#include "Support/Debug.h"
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#include "Support/Statistic.h"
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#include "Support/StringExtras.h"
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namespace {
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Statistic<> NumReplaced("scalarrepl", "Number of alloca's broken up");
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Statistic<> NumPromoted("scalarrepl", "Number of alloca's promoted");
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struct SROA : public FunctionPass {
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bool runOnFunction(Function &F);
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bool performScalarRepl(Function &F);
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bool performPromotion(Function &F);
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// getAnalysisUsage - This pass does not require any passes, but we know it
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// will not alter the CFG, so say so.
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<DominanceFrontier>();
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AU.addRequired<TargetData>();
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AU.setPreservesCFG();
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}
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@ -43,11 +57,52 @@ namespace {
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Pass *createScalarReplAggregatesPass() { return new SROA(); }
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// runOnFunction - This algorithm is a simple worklist driven algorithm, which
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// runs on all of the malloc/alloca instructions in the function, removing them
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// if they are only used by getelementptr instructions.
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//
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bool SROA::runOnFunction(Function &F) {
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bool Changed = false, LocalChange;
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do {
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LocalChange = performScalarRepl(F);
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LocalChange |= performPromotion(F);
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Changed |= LocalChange;
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} while (LocalChange);
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return Changed;
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}
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bool SROA::performPromotion(Function &F) {
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std::vector<AllocaInst*> Allocas;
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const TargetData &TD = getAnalysis<TargetData>();
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BasicBlock &BB = F.getEntryNode(); // Get the entry node for the function
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bool Changed = false;
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while (1) {
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Allocas.clear();
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// Find allocas that are safe to promote, by looking at all instructions in
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// the entry node
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for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
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if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
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if (isAllocaPromotable(AI, TD))
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Allocas.push_back(AI);
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if (Allocas.empty()) break;
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PromoteMemToReg(Allocas, getAnalysis<DominanceFrontier>(), TD);
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NumPromoted += Allocas.size();
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Changed = true;
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}
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return Changed;
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}
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// performScalarRepl - This algorithm is a simple worklist driven algorithm,
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// which runs on all of the malloc/alloca instructions in the function, removing
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// them if they are only used by getelementptr instructions.
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//
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bool SROA::performScalarRepl(Function &F) {
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std::vector<AllocationInst*> WorkList;
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// Scan the entry basic block, adding any alloca's and mallocs to the worklist
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