Split mem2reg promotion into two parts: a function which does the work, and

a pass which wraps the function.  This allows other passes to use the functionality

llvm-svn: 5610

1 files changed, 59 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/Mem2Reg.cpp b/llvm/lib/Transforms/Scalar/Mem2Reg.cpp
new file mode 100644
index 00000000000..6fbb43f6c3f
--- /dev/null
+++ b/llvm/lib/Transforms/Scalar/Mem2Reg.cpp
@@ -0,0 +1,59 @@
+//===- Mem2Reg.cpp - The -mem2reg pass, a wrapper around the Utils lib ----===//
+//
+// 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/Analysis/Dominators.h"
+#include "llvm/iMemory.h"
+#include "llvm/Function.h"
+#include "Support/Statistic.h"
+
+namespace {
+  Statistic<> NumPromoted("mem2reg", "Number of alloca's promoted");
+
+  struct 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<DominanceFrontier>();
+      AU.setPreservesCFG();
+    }
+  };
+
+  RegisterOpt<PromotePass> X("mem2reg", "Promote Memory to Register");
+}  // end of anonymous namespace
+
+bool PromotePass::runOnFunction(Function &F) {
+  std::vector<AllocaInst*> Allocas;
+
+  BasicBlock &BB = F.getEntryNode();  // Get the entry node for the function
+
+  // 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))
+        Allocas.push_back(AI);
+
+  if (!Allocas.empty()) {
+    PromoteMemToReg(Allocas, getAnalysis<DominanceFrontier>());
+    NumPromoted += Allocas.size();
+    return true;
+  }
+  return false;
+}
+
+// createPromoteMemoryToRegister - Provide an entry point to create this pass.
+//
+Pass *createPromoteMemoryToRegister() {
+  return new PromotePass();
+}