It's not necessary to do rounding for alloca operations when the requested
alignment is equal to the stack alignment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/GCSE.cpp b/lib/Transforms/Scalar/GCSE.cpp
new file mode 100644
index 0000000..93ed8c4
--- /dev/null
+++ b/lib/Transforms/Scalar/GCSE.cpp
@@ -0,0 +1,201 @@
+//===-- GCSE.cpp - SSA-based Global Common Subexpression Elimination ------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass is designed to be a very quick global transformation that
+// eliminates global common subexpressions from a function. It does this by
+// using an existing value numbering implementation to identify the common
+// subexpressions, eliminating them when possible.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "gcse"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Instructions.h"
+#include "llvm/Function.h"
+#include "llvm/Type.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/ValueNumbering.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Compiler.h"
+#include <algorithm>
+using namespace llvm;
+
+STATISTIC(NumInstRemoved, "Number of instructions removed");
+STATISTIC(NumLoadRemoved, "Number of loads removed");
+STATISTIC(NumCallRemoved, "Number of calls removed");
+STATISTIC(NumNonInsts , "Number of instructions removed due "
+ "to non-instruction values");
+STATISTIC(NumArgsRepl , "Number of function arguments replaced "
+ "with constant values");
+namespace {
+ struct VISIBILITY_HIDDEN GCSE : public FunctionPass {
+ static char ID; // Pass identification, replacement for typeid
+ GCSE() : FunctionPass((intptr_t)&ID) {}
+
+ virtual bool runOnFunction(Function &F);
+
+ private:
+ void ReplaceInstructionWith(Instruction *I, Value *V);
+
+ // This transformation requires dominator and immediate dominator info
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ AU.addRequired<DominatorTree>();
+ AU.addRequired<ValueNumbering>();
+ }
+ };
+
+ char GCSE::ID = 0;
+ RegisterPass<GCSE> X("gcse", "Global Common Subexpression Elimination");
+}
+
+// createGCSEPass - The public interface to this file...
+FunctionPass *llvm::createGCSEPass() { return new GCSE(); }
+
+// GCSE::runOnFunction - This is the main transformation entry point for a
+// function.
+//
+bool GCSE::runOnFunction(Function &F) {
+ bool Changed = false;
+
+ // Get pointers to the analysis results that we will be using...
+ DominatorTree &DT = getAnalysis<DominatorTree>();
+ ValueNumbering &VN = getAnalysis<ValueNumbering>();
+
+ std::vector<Value*> EqualValues;
+
+ // Check for value numbers of arguments. If the value numbering
+ // implementation can prove that an incoming argument is a constant or global
+ // value address, substitute it, making the argument dead.
+ for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;++AI)
+ if (!AI->use_empty()) {
+ VN.getEqualNumberNodes(AI, EqualValues);
+ if (!EqualValues.empty()) {
+ for (unsigned i = 0, e = EqualValues.size(); i != e; ++i)
+ if (isa<Constant>(EqualValues[i])) {
+ AI->replaceAllUsesWith(EqualValues[i]);
+ ++NumArgsRepl;
+ Changed = true;
+ break;
+ }
+ EqualValues.clear();
+ }
+ }
+
+ // Traverse the CFG of the function in dominator order, so that we see each
+ // instruction after we see its operands.
+ for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
+ E = df_end(DT.getRootNode()); DI != E; ++DI) {
+ BasicBlock *BB = DI->getBlock();
+
+ // Remember which instructions we've seen in this basic block as we scan.
+ std::set<Instruction*> BlockInsts;
+
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
+ Instruction *Inst = I++;
+
+ if (Constant *C = ConstantFoldInstruction(Inst)) {
+ ReplaceInstructionWith(Inst, C);
+ } else if (Inst->getType() != Type::VoidTy) {
+ // If this instruction computes a value, try to fold together common
+ // instructions that compute it.
+ //
+ VN.getEqualNumberNodes(Inst, EqualValues);
+
+ // If this instruction computes a value that is already computed
+ // elsewhere, try to recycle the old value.
+ if (!EqualValues.empty()) {
+ if (Inst == &*BB->begin())
+ I = BB->end();
+ else {
+ I = Inst; --I;
+ }
+
+ // First check to see if we were able to value number this instruction
+ // to a non-instruction value. If so, prefer that value over other
+ // instructions which may compute the same thing.
+ for (unsigned i = 0, e = EqualValues.size(); i != e; ++i)
+ if (!isa<Instruction>(EqualValues[i])) {
+ ++NumNonInsts; // Keep track of # of insts repl with values
+
+ // Change all users of Inst to use the replacement and remove it
+ // from the program.
+ ReplaceInstructionWith(Inst, EqualValues[i]);
+ Inst = 0;
+ EqualValues.clear(); // don't enter the next loop
+ break;
+ }
+
+ // If there were no non-instruction values that this instruction
+ // produces, find a dominating instruction that produces the same
+ // value. If we find one, use it's value instead of ours.
+ for (unsigned i = 0, e = EqualValues.size(); i != e; ++i) {
+ Instruction *OtherI = cast<Instruction>(EqualValues[i]);
+ bool Dominates = false;
+ if (OtherI->getParent() == BB)
+ Dominates = BlockInsts.count(OtherI);
+ else
+ Dominates = DT.dominates(OtherI->getParent(), BB);
+
+ if (Dominates) {
+ // Okay, we found an instruction with the same value as this one
+ // and that dominates this one. Replace this instruction with the
+ // specified one.
+ ReplaceInstructionWith(Inst, OtherI);
+ Inst = 0;
+ break;
+ }
+ }
+
+ EqualValues.clear();
+
+ if (Inst) {
+ I = Inst; ++I; // Deleted no instructions
+ } else if (I == BB->end()) { // Deleted first instruction
+ I = BB->begin();
+ } else { // Deleted inst in middle of block.
+ ++I;
+ }
+ }
+
+ if (Inst)
+ BlockInsts.insert(Inst);
+ }
+ }
+ }
+
+ // When the worklist is empty, return whether or not we changed anything...
+ return Changed;
+}
+
+
+void GCSE::ReplaceInstructionWith(Instruction *I, Value *V) {
+ if (isa<LoadInst>(I))
+ ++NumLoadRemoved; // Keep track of loads eliminated
+ if (isa<CallInst>(I))
+ ++NumCallRemoved; // Keep track of calls eliminated
+ ++NumInstRemoved; // Keep track of number of insts eliminated
+
+ // Update value numbering
+ getAnalysis<ValueNumbering>().deleteValue(I);
+
+ I->replaceAllUsesWith(V);
+
+ if (InvokeInst *II = dyn_cast<InvokeInst>(I)) {
+ // Removing an invoke instruction requires adding a branch to the normal
+ // destination and removing PHI node entries in the exception destination.
+ new BranchInst(II->getNormalDest(), II);
+ II->getUnwindDest()->removePredecessor(II->getParent());
+ }
+
+ // Erase the instruction from the program.
+ I->getParent()->getInstList().erase(I);
+}