From 0928bc13137a7a44af1daaa4dfe50788fd89cbfd Mon Sep 17 00:00:00 2001
From: Robert Widmann <devteam.codafi@gmail.com>
Date: Wed, 29 Mar 2017 18:21:22 -0400
Subject: [PATCH] Model terminator instructions

---
 Sources/LLVM/BasicBlock.swift  |  7 +++++++
 Sources/LLVM/Instruction.swift | 27 +++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/Sources/LLVM/BasicBlock.swift b/Sources/LLVM/BasicBlock.swift
index 63ee2121..a00b87ed 100644
--- a/Sources/LLVM/BasicBlock.swift
+++ b/Sources/LLVM/BasicBlock.swift
@@ -40,6 +40,13 @@ public struct BasicBlock: IRValue {
     return Instruction(llvm: val)
   }
 
+  /// Returns the terminator instruction if this basic block is well formed or 
+  /// `nil` if it is not well formed.
+  public var terminator: TerminatorInstruction? {
+    guard let term = LLVMGetBasicBlockTerminator(llvm) else { return nil }
+    return TerminatorInstruction(llvm: term)
+  }
+
   /// Returns the parent function of this basic block, if it exists.
   public var parent: Function? {
     guard let functionRef = LLVMGetBasicBlockParent(llvm) else { return nil }
diff --git a/Sources/LLVM/Instruction.swift b/Sources/LLVM/Instruction.swift
index 0d6c7bc1..4dbf10ad 100644
--- a/Sources/LLVM/Instruction.swift
+++ b/Sources/LLVM/Instruction.swift
@@ -51,3 +51,30 @@ public struct Instruction: IRValue {
     }
   }
 }
+
+/// A `TerminatorInstruction` represents an instruction that terminates a 
+/// basic block.
+public struct TerminatorInstruction {
+  internal let llvm: LLVMValueRef
+
+  /// Creates a `TerminatorInstruction` from an `LLVMValueRef` object.
+  public init(llvm: LLVMValueRef) {
+    self.llvm = llvm
+  }
+
+  /// Retrieves the number of successors of this terminator instruction.
+  public var successorCount: Int {
+    return Int(LLVMGetNumSuccessors(llvm))
+  }
+
+  /// Returns the successor block at the specified index, if it exists.
+  public func getSuccessor(at idx: Int) -> BasicBlock? {
+    guard let succ = LLVMGetSuccessor(llvm, UInt32(idx)) else { return nil }
+    return BasicBlock(llvm: succ)
+  }
+
+  /// Updates the successor block at the specified index.
+  public func setSuccessor(at idx: Int, to bb: BasicBlock) {
+    LLVMSetSuccessor(llvm, UInt32(idx), bb.asLLVM())
+  }
+}