vendor/llvm/llvm-r72732

1 files changed, 89 insertions, 0 deletions

diff --git a/lib/Transforms/IPO/IndMemRemoval.cpp b/lib/Transforms/IPO/IndMemRemoval.cpp
new file mode 100644
index 0000000000000..b55dea2c759c3
--- /dev/null
+++ b/lib/Transforms/IPO/IndMemRemoval.cpp
@@ -0,0 +1,89 @@
+//===-- IndMemRemoval.cpp - Remove indirect allocations and frees ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass finds places where memory allocation functions may escape into
+// indirect land.  Some transforms are much easier (aka possible) only if free 
+// or malloc are not called indirectly.
+// Thus find places where the address of memory functions are taken and construct
+// bounce functions with direct calls of those functions.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "indmemrem"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Pass.h"
+#include "llvm/Module.h"
+#include "llvm/Instructions.h"
+#include "llvm/Type.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Compiler.h"
+using namespace llvm;
+
+STATISTIC(NumBounceSites, "Number of sites modified");
+STATISTIC(NumBounce     , "Number of bounce functions created");
+
+namespace {
+  class VISIBILITY_HIDDEN IndMemRemPass : public ModulePass {
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    IndMemRemPass() : ModulePass(&ID) {}
+
+    virtual bool runOnModule(Module &M);
+  };
+} // end anonymous namespace
+
+char IndMemRemPass::ID = 0;
+static RegisterPass<IndMemRemPass>
+X("indmemrem","Indirect Malloc and Free Removal");
+
+bool IndMemRemPass::runOnModule(Module &M) {
+  // In theory, all direct calls of malloc and free should be promoted
+  // to intrinsics.  Therefore, this goes through and finds where the
+  // address of free or malloc are taken and replaces those with bounce
+  // functions, ensuring that all malloc and free that might happen
+  // happen through intrinsics.
+  bool changed = false;
+  if (Function* F = M.getFunction("free")) {
+    if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
+      Function* FN = Function::Create(F->getFunctionType(),
+                                      GlobalValue::LinkOnceAnyLinkage,
+                                      "free_llvm_bounce", &M);
+      BasicBlock* bb = BasicBlock::Create("entry",FN);
+      Instruction* R = ReturnInst::Create(bb);
+      new FreeInst(FN->arg_begin(), R);
+      ++NumBounce;
+      NumBounceSites += F->getNumUses();
+      F->replaceAllUsesWith(FN);
+      changed = true;
+    }
+  }
+  if (Function* F = M.getFunction("malloc")) {
+    if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
+      Function* FN = Function::Create(F->getFunctionType(), 
+                                      GlobalValue::LinkOnceAnyLinkage,
+                                      "malloc_llvm_bounce", &M);
+      FN->setDoesNotAlias(0);
+      BasicBlock* bb = BasicBlock::Create("entry",FN);
+      Instruction* c = CastInst::CreateIntegerCast(
+          FN->arg_begin(), Type::Int32Ty, false, "c", bb);
+      Instruction* a = new MallocInst(Type::Int8Ty, c, "m", bb);
+      ReturnInst::Create(a, bb);
+      ++NumBounce;
+      NumBounceSites += F->getNumUses();
+      F->replaceAllUsesWith(FN);
+      changed = true;
+    }
+  }
+  return changed;
+}
+
+ModulePass *llvm::createIndMemRemPass() {
+  return new IndMemRemPass();
+}