Add missing newlines at EOF (for clang++).

[oota-llvm.git] / include / llvm / Instruction.h

diff --git a/include/llvm/Instruction.h b/include/llvm/Instruction.h
index 1d1f0f42d12fcccfed1b58f2e0e27f224233a7d9..07b3231aa14ba2fd78782b54bf03175caded0817 100644 (file)
--- a/include/llvm/Instruction.h
+++ b/include/llvm/Instruction.h
@@ -38,6 +38,7 @@ protected:
               Instruction *InsertBefore = 0);
   Instruction(const Type *Ty, unsigned iType, Use *Ops, unsigned NumOps,
               BasicBlock *InsertAtEnd);
+  virtual Instruction *clone_impl() const = 0;
 public:
   // Out of line virtual method, so the vtable, etc has a home.
   ~Instruction();
@@ -47,13 +48,18 @@ public:
   ///   * The instruction has no parent
   ///   * The instruction has no name
   ///
-  virtual Instruction *clone(LLVMContext &Context) const = 0;
+  Instruction *clone() const;
 
   /// isIdenticalTo - Return true if the specified instruction is exactly
   /// identical to the current one.  This means that all operands match and any
   /// extra information (e.g. load is volatile) agree.
   bool isIdenticalTo(const Instruction *I) const;
 
+  /// isIdenticalToWhenDefined - This is like isIdenticalTo, except that it
+  /// ignores the SubclassOptionalData flags, which specify conditions
+  /// under which the instruction's result is undefined.
+  bool isIdenticalToWhenDefined(const Instruction *I) const;
+
   /// This function determines if the specified instruction executes the same
   /// operation as the current one. This means that the opcodes, type, operand
   /// types and any other factors affecting the operation must be the same. This
@@ -182,19 +188,32 @@ public:
 
   /// mayHaveSideEffects - Return true if the instruction may have side effects.
   ///
+  /// Note that this does not consider malloc and alloca to have side
+  /// effects because the newly allocated memory is completely invisible to
+  /// instructions which don't used the returned value.  For cases where this
+  /// matters, isSafeToSpeculativelyExecute may be more appropriate.
   bool mayHaveSideEffects() const {
     return mayWriteToMemory() || mayThrow();
   }
 
   /// isSafeToSpeculativelyExecute - Return true if the instruction does not
   /// have any effects besides calculating the result and does not have
-  /// undefined behavior. Unlike in mayHaveSideEffects(), allocating memory
-  /// is considered an effect.
+  /// undefined behavior.
+  ///
+  /// This method never returns true for an instruction that returns true for
+  /// mayHaveSideEffects; however, this method also does some other checks in
+  /// addition. It checks for undefined behavior, like dividing by zero or
+  /// loading from an invalid pointer (but not for undefined results, like a
+  /// shift with a shift amount larger than the width of the result). It checks
+  /// for malloc and alloca because speculatively executing them might cause a
+  /// memory leak. It also returns false for instructions related to control
+  /// flow, specifically terminators and PHI nodes.
   ///
   /// This method only looks at the instruction itself and its operands, so if
   /// this method returns true, it is safe to move the instruction as long as
-  /// the operands still dominate it.  However, care must be taken with
-  /// instructions which read memory.
+  /// the correct dominance relationships for the operands and users hold.
+  /// However, this method can return true for instructions that read memory;
+  /// for such instructions, moving them may change the resulting value.
   bool isSafeToSpeculativelyExecute() const;
 
   /// Methods for support type inquiry through isa, cast, and dyn_cast: