X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FInstruction.h;h=924b19554a807a529a84631d57ad43f656c07379;hb=b834a7b73ce0dcf8fbf8d8b0d62f69e4b78059ad;hp=856531c90685f8a82698fc0856ba2888c5be2ece;hpb=e30173ac3396510bd0bb26a66fd615ff9083436d;p=oota-llvm.git

diff --git a/include/llvm/Instruction.h b/include/llvm/Instruction.h
index 856531c9068..924b19554a8 100644
--- a/include/llvm/Instruction.h
+++ b/include/llvm/Instruction.h
@@ -20,6 +20,8 @@
 
 namespace llvm {
 
+class LLVMContext;
+
 template<typename ValueSubClass, typename ItemParentClass>
   class SymbolTableListTraits;
 
@@ -40,20 +42,12 @@ public:
   // Out of line virtual method, so the vtable, etc has a home.
   ~Instruction();
   
-  /// mayWriteToMemory - Return true if this instruction may modify memory.
-  ///
-  bool mayWriteToMemory() const;
-
-  /// mayReadFromMemory - Return true if this instruction may read memory.
-  ///
-  bool mayReadFromMemory() const;
-  
   /// clone() - Create a copy of 'this' instruction that is identical in all
   /// ways except the following:
   ///   * The instruction has no parent
   ///   * The instruction has no name
   ///
-  virtual Instruction *clone() const = 0;
+  virtual Instruction *clone(LLVMContext &Context) const = 0;
 
   /// isIdenticalTo - Return true if the specified instruction is exactly
   /// identical to the current one.  This means that all operands match and any
@@ -144,8 +138,7 @@ public:
     return getOpcode() == Shl || getOpcode() == LShr;
   }
 
-  /// isLogicalShift - Return true if this is a logical shift left or a logical
-  /// shift right.
+  /// isArithmeticShift - Return true if this is an arithmetic shift right.
   inline bool isArithmeticShift() const {
     return getOpcode() == AShr;
   }
@@ -175,12 +168,47 @@ public:
   bool isCommutative() const { return isCommutative(getOpcode()); }
   static bool isCommutative(unsigned op);
 
-  /// isTrapping - Return true if the instruction may trap.
+  /// mayWriteToMemory - Return true if this instruction may modify memory.
+  ///
+  bool mayWriteToMemory() const;
+
+  /// mayReadFromMemory - Return true if this instruction may read memory.
+  ///
+  bool mayReadFromMemory() const;
+
+  /// mayThrow - Return true if this instruction may throw an exception.
+  ///
+  bool mayThrow() const;
+
+  /// mayHaveSideEffects - Return true if the instruction may have side effects.
   ///
-  bool isTrapping() const {
-    return isTrapping(getOpcode());
+  /// 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();
   }
-  static bool isTrapping(unsigned op);
+
+  /// isSafeToSpeculativelyExecute - Return true if the instruction does not
+  /// have any effects besides calculating the result and does not have
+  /// 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 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:
   static inline bool classof(const Instruction *) { return true; }