1 files changed, 138 insertions, 0 deletions
diff --git a/tools/llvm-objdump/MCFunction.cpp b/tools/llvm-objdump/MCFunction.cpp
new file mode 100644
index 0000000..5c67f1b
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+++ b/tools/llvm-objdump/MCFunction.cpp
@@ -0,0 +1,138 @@
+//===-- MCFunction.cpp ----------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the algorithm to break down a region of machine code
+// into basic blocks and try to reconstruct a CFG from it.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MCFunction.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/MC/MCDisassembler.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCInstPrinter.h"
+#include "llvm/MC/MCInstrAnalysis.h"
+#include "llvm/MC/MCInstrDesc.h"
+#include "llvm/MC/MCInstrInfo.h"
+#include "llvm/Support/MemoryObject.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/system_error.h"
+#include <set>
+using namespace llvm;
+
+MCFunction
+MCFunction::createFunctionFromMC(StringRef Name, const MCDisassembler *DisAsm,
+                                 const MemoryObject &Region, uint64_t Start,
+                                 uint64_t End, const MCInstrAnalysis *Ana,
+                                 raw_ostream &DebugOut,
+                                 SmallVectorImpl<uint64_t> &Calls) {
+  std::vector<MCDecodedInst> Instructions;
+  std::set<uint64_t> Splits;
+  Splits.insert(Start);
+  uint64_t Size;
+
+  MCFunction f(Name);
+
+  {
+  DenseSet<uint64_t> VisitedInsts;
+  SmallVector<uint64_t, 16> WorkList;
+  WorkList.push_back(Start);
+  // Disassemble code and gather basic block split points.
+  while (!WorkList.empty()) {
+    uint64_t Index = WorkList.pop_back_val();
+    if (VisitedInsts.find(Index) != VisitedInsts.end())
+      continue; // Already visited this location.
+
+    for (;Index < End; Index += Size) {
+      VisitedInsts.insert(Index);
+
+      MCInst Inst;
+      if (DisAsm->getInstruction(Inst, Size, Region, Index, DebugOut, nulls())){
+        Instructions.push_back(MCDecodedInst(Index, Size, Inst));
+        if (Ana->isBranch(Inst)) {
+          uint64_t targ = Ana->evaluateBranch(Inst, Index, Size);
+          if (targ != -1ULL && targ == Index+Size)
+            continue; // Skip nop jumps.
+
+          // If we could determine the branch target, make a note to start a
+          // new basic block there and add the target to the worklist.
+          if (targ != -1ULL) {
+            Splits.insert(targ);
+            WorkList.push_back(targ);
+            WorkList.push_back(Index+Size);
+          }
+          Splits.insert(Index+Size);
+          break;
+        } else if (Ana->isReturn(Inst)) {
+          // Return instruction. This basic block ends here.
+          Splits.insert(Index+Size);
+          break;
+        } else if (Ana->isCall(Inst)) {
+          uint64_t targ = Ana->evaluateBranch(Inst, Index, Size);
+          // Add the call to the call list if the destination is known.
+          if (targ != -1ULL && targ != Index+Size)
+            Calls.push_back(targ);
+        }
+      } else {
+        errs().write_hex(Index) << ": warning: invalid instruction encoding\n";
+        if (Size == 0)
+          Size = 1; // skip illegible bytes
+      }
+    }
+  }
+  }
+
+  // Make sure the instruction list is sorted.
+  std::sort(Instructions.begin(), Instructions.end());
+
+  // Create basic blocks.
+  unsigned ii = 0, ie = Instructions.size();
+  for (std::set<uint64_t>::iterator spi = Splits.begin(),
+       spe = llvm::prior(Splits.end()); spi != spe; ++spi) {
+    MCBasicBlock BB;
+    uint64_t BlockEnd = *llvm::next(spi);
+    // Add instructions to the BB.
+    for (; ii != ie; ++ii) {
+      if (Instructions[ii].Address < *spi ||
+          Instructions[ii].Address >= BlockEnd)
+        break;
+      BB.addInst(Instructions[ii]);
+    }
+    f.addBlock(*spi, BB);
+  }
+
+  std::sort(f.Blocks.begin(), f.Blocks.end());
+
+  // Calculate successors of each block.
+  for (MCFunction::iterator i = f.begin(), e = f.end(); i != e; ++i) {
+    MCBasicBlock &BB = const_cast<MCBasicBlock&>(i->second);
+    if (BB.getInsts().empty()) continue;
+    const MCDecodedInst &Inst = BB.getInsts().back();
+
+    if (Ana->isBranch(Inst.Inst)) {
+      uint64_t targ = Ana->evaluateBranch(Inst.Inst, Inst.Address, Inst.Size);
+      if (targ == -1ULL) {
+        // Indirect branch. Bail and add all blocks of the function as a
+        // successor.
+        for (MCFunction::iterator i = f.begin(), e = f.end(); i != e; ++i)
+          BB.addSucc(i->first);
+      } else if (targ != Inst.Address+Inst.Size)
+        BB.addSucc(targ);
+      // Conditional branches can also fall through to the next block.
+      if (Ana->isConditionalBranch(Inst.Inst) && llvm::next(i) != e)
+        BB.addSucc(llvm::next(i)->first);
+    } else {
+      // No branch. Fall through to the next block.
+      if (!Ana->isReturn(Inst.Inst) && llvm::next(i) != e)
+        BB.addSucc(llvm::next(i)->first);
+    }
+  }
+
+  return f;
+}