1 files changed, 116 insertions, 0 deletions
diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
new file mode 100644
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+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
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+//===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
+//
+//                     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 family of functions perform manipulations on basic blocks, and
+// instructions contained within basic blocks.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/Constant.h"
+#include "llvm/Type.h"
+#include <algorithm>
+using namespace llvm;
+
+/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
+/// with a value, then remove and delete the original instruction.
+///
+void llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL,
+                                BasicBlock::iterator &BI, Value *V) {
+  Instruction &I = *BI;
+  // Replaces all of the uses of the instruction with uses of the value
+  I.replaceAllUsesWith(V);
+
+  std::string OldName = I.getName();
+
+  // Delete the unnecessary instruction now...
+  BI = BIL.erase(BI);
+
+  // Make sure to propagate a name if there is one already.
+  if (!OldName.empty() && !V->hasName())
+    V->setName(OldName);
+}
+
+
+/// ReplaceInstWithInst - Replace the instruction specified by BI with the
+/// instruction specified by I.  The original instruction is deleted and BI is
+/// updated to point to the new instruction.
+///
+void llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL,
+                               BasicBlock::iterator &BI, Instruction *I) {
+  assert(I->getParent() == 0 &&
+         "ReplaceInstWithInst: Instruction already inserted into basic block!");
+
+  // Insert the new instruction into the basic block...
+  BasicBlock::iterator New = BIL.insert(BI, I);
+
+  // Replace all uses of the old instruction, and delete it.
+  ReplaceInstWithValue(BIL, BI, I);
+
+  // Move BI back to point to the newly inserted instruction
+  BI = New;
+}
+
+/// ReplaceInstWithInst - Replace the instruction specified by From with the
+/// instruction specified by To.
+///
+void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) {
+  BasicBlock::iterator BI(From);
+  ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
+}
+
+/// RemoveSuccessor - Change the specified terminator instruction such that its
+/// successor #SuccNum no longer exists.  Because this reduces the outgoing
+/// degree of the current basic block, the actual terminator instruction itself
+/// may have to be changed.  In the case where the last successor of the block is
+/// deleted, a return instruction is inserted in its place which can cause a
+/// surprising change in program behavior if it is not expected.
+///
+void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
+  assert(SuccNum < TI->getNumSuccessors() &&
+         "Trying to remove a nonexistant successor!");
+
+  // If our old successor block contains any PHI nodes, remove the entry in the
+  // PHI nodes that comes from this branch...
+  //
+  BasicBlock *BB = TI->getParent();
+  TI->getSuccessor(SuccNum)->removePredecessor(BB);
+
+  TerminatorInst *NewTI = 0;
+  switch (TI->getOpcode()) {
+  case Instruction::Br:
+    // If this is a conditional branch... convert to unconditional branch.
+    if (TI->getNumSuccessors() == 2) {
+      cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum));
+    } else {                    // Otherwise convert to a return instruction...
+      Value *RetVal = 0;
+
+      // Create a value to return... if the function doesn't return null...
+      if (BB->getParent()->getReturnType() != Type::VoidTy)
+        RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
+
+      // Create the return...
+      NewTI = new ReturnInst(RetVal);
+    }
+    break;
+
+  case Instruction::Invoke:    // Should convert to call
+  case Instruction::Switch:    // Should remove entry
+  default:
+  case Instruction::Ret:       // Cannot happen, has no successors!
+    assert(0 && "Unhandled terminator instruction type in RemoveSuccessor!");
+    abort();
+  }
+
+  if (NewTI)   // If it's a different instruction, replace.
+    ReplaceInstWithInst(TI, NewTI);
+}
+