1 files changed, 125 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/Reg2Mem.cpp b/lib/Transforms/Scalar/Reg2Mem.cpp
new file mode 100644
index 0000000..46b2952
--- /dev/null
+++ b/lib/Transforms/Scalar/Reg2Mem.cpp
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+//===- Reg2Mem.cpp - Convert registers to allocas -------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file demotes all registers to memory references.  It is intented to be
+// the inverse of PromoteMemoryToRegister.  By converting to loads, the only
+// values live accross basic blocks are allocas and loads before phi nodes.
+// It is intended that this should make CFG hacking much easier.
+// To make later hacking easier, the entry block is split into two, such that
+// all introduced allocas and nothing else are in the entry block.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "reg2mem"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Pass.h"
+#include "llvm/Function.h"
+#include "llvm/Module.h"
+#include "llvm/BasicBlock.h"
+#include "llvm/Instructions.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/CFG.h"
+#include <list>
+using namespace llvm;
+
+STATISTIC(NumRegsDemoted, "Number of registers demoted");
+STATISTIC(NumPhisDemoted, "Number of phi-nodes demoted");
+
+namespace {
+  struct VISIBILITY_HIDDEN RegToMem : public FunctionPass {
+    static char ID; // Pass identification, replacement for typeid
+    RegToMem() : FunctionPass(&ID) {}
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequiredID(BreakCriticalEdgesID);
+      AU.addPreservedID(BreakCriticalEdgesID);
+    }
+
+   bool valueEscapes(Instruction* i) {
+      BasicBlock* bb = i->getParent();
+      for (Value::use_iterator ii = i->use_begin(), ie = i->use_end();
+           ii != ie; ++ii)
+        if (cast<Instruction>(*ii)->getParent() != bb ||
+            isa<PHINode>(*ii))
+          return true;
+      return false;
+    }
+
+    virtual bool runOnFunction(Function &F) {
+      if (!F.isDeclaration()) {
+        // Insert all new allocas into entry block.
+        BasicBlock* BBEntry = &F.getEntryBlock();
+        assert(pred_begin(BBEntry) == pred_end(BBEntry) &&
+               "Entry block to function must not have predecessors!");
+
+        // Find first non-alloca instruction and create insertion point. This is
+        // safe if block is well-formed: it always have terminator, otherwise
+        // we'll get and assertion.
+        BasicBlock::iterator I = BBEntry->begin();
+        while (isa<AllocaInst>(I)) ++I;
+
+        CastInst *AllocaInsertionPoint =
+          CastInst::Create(Instruction::BitCast,
+                           Constant::getNullValue(Type::Int32Ty), Type::Int32Ty,
+                           "reg2mem alloca point", I);
+
+        // Find the escaped instructions. But don't create stack slots for
+        // allocas in entry block.
+        std::list<Instruction*> worklist;
+        for (Function::iterator ibb = F.begin(), ibe = F.end();
+             ibb != ibe; ++ibb)
+          for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
+               iib != iie; ++iib) {
+            if (!(isa<AllocaInst>(iib) && iib->getParent() == BBEntry) &&
+                valueEscapes(iib)) {
+              worklist.push_front(&*iib);
+            }
+          }
+
+        // Demote escaped instructions
+        NumRegsDemoted += worklist.size();
+        for (std::list<Instruction*>::iterator ilb = worklist.begin(), 
+               ile = worklist.end(); ilb != ile; ++ilb)
+          DemoteRegToStack(**ilb, false, AllocaInsertionPoint);
+
+        worklist.clear();
+
+        // Find all phi's
+        for (Function::iterator ibb = F.begin(), ibe = F.end();
+             ibb != ibe; ++ibb)
+          for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
+               iib != iie; ++iib)
+            if (isa<PHINode>(iib))
+              worklist.push_front(&*iib);
+
+        // Demote phi nodes
+        NumPhisDemoted += worklist.size();
+        for (std::list<Instruction*>::iterator ilb = worklist.begin(), 
+               ile = worklist.end(); ilb != ile; ++ilb)
+          DemotePHIToStack(cast<PHINode>(*ilb), AllocaInsertionPoint);
+
+        return true;
+      }
+      return false;
+    }
+  };
+}
+  
+char RegToMem::ID = 0;
+static RegisterPass<RegToMem>
+X("reg2mem", "Demote all values to stack slots");
+
+// createDemoteRegisterToMemory - Provide an entry point to create this pass.
+//
+const PassInfo *const llvm::DemoteRegisterToMemoryID = &X;
+FunctionPass *llvm::createDemoteRegisterToMemoryPass() {
+  return new RegToMem();
+}