Add some advice

llvm-svn: 29324

1 files changed, 91 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/Mem2Reg.cpp b/llvm/lib/Transforms/Utils/Mem2Reg.cpp
new file mode 100644
index 0000000..d1b2c50
--- /dev/null
+++ b/llvm/lib/Transforms/Utils/Mem2Reg.cpp
@@ -0,0 +1,91 @@
+//===- Mem2Reg.cpp - The -mem2reg pass, a wrapper around the Utils lib ----===//
+//
+//                     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 a simple pass wrapper around the PromoteMemToReg function call
+// exposed by the Utils library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/PromoteMemToReg.h"
+#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Instructions.h"
+#include "llvm/Function.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Visibility.h"
+using namespace llvm;
+
+namespace {
+  Statistic<> NumPromoted("mem2reg", "Number of alloca's promoted");
+
+  struct VISIBILITY_HIDDEN PromotePass : public FunctionPass {
+    // runOnFunction - To run this pass, first we calculate the alloca
+    // instructions that are safe for promotion, then we promote each one.
+    //
+    virtual bool runOnFunction(Function &F);
+
+    // getAnalysisUsage - We need dominance frontiers
+    //
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequired<DominatorTree>();
+      AU.addRequired<DominanceFrontier>();
+      AU.addRequired<TargetData>();
+      AU.setPreservesCFG();
+      // This is a cluster of orthogonal Transforms	
+      AU.addPreserved<UnifyFunctionExitNodes>();
+      AU.addPreservedID(LowerSelectID);
+      AU.addPreservedID(LowerSwitchID);
+      AU.addPreservedID(LowerInvokePassID);
+      AU.addPreservedID(LowerAllocationsID);
+    }
+  };
+
+  RegisterOpt<PromotePass> X("mem2reg", "Promote Memory to Register");
+}  // end of anonymous namespace
+
+bool PromotePass::runOnFunction(Function &F) {
+  std::vector<AllocaInst*> Allocas;
+  const TargetData &TD = getAnalysis<TargetData>();
+
+  BasicBlock &BB = F.getEntryBlock();  // Get the entry node for the function
+
+  bool Changed  = false;
+
+  DominatorTree     &DT = getAnalysis<DominatorTree>();
+  DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
+
+  while (1) {
+    Allocas.clear();
+
+    // Find allocas that are safe to promote, by looking at all instructions in
+    // the entry node
+    for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
+      if (AllocaInst *AI = dyn_cast<AllocaInst>(I))       // Is it an alloca?
+        if (isAllocaPromotable(AI, TD))
+          Allocas.push_back(AI);
+
+    if (Allocas.empty()) break;
+
+    PromoteMemToReg(Allocas, DT, DF, TD);
+    NumPromoted += Allocas.size();
+    Changed = true;
+  }
+
+  return Changed;
+}
+
+// Publically exposed interface to pass...
+const PassInfo *llvm::PromoteMemoryToRegisterID = X.getPassInfo();
+// createPromoteMemoryToRegister - Provide an entry point to create this pass.
+//
+FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
+  return new PromotePass();
+}