Allow readonly functions to unwind exceptions. Teach

the optimizers about this.  For example, a readonly
function with no uses cannot be removed unless it is
also marked nounwind.

llvm-svn: 71071

1 files changed, 18 insertions, 8 deletions

diff --git a/llvm/include/llvm/Instruction.h b/llvm/include/llvm/Instruction.h
index 0a39b08461d..7d946e85a6d 100644
--- a/llvm/include/llvm/Instruction.h
+++ b/llvm/include/llvm/Instruction.h
@@ -40,14 +40,6 @@ 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
@@ -181,6 +173,24 @@ public:
   }
   static bool isTrapping(unsigned op);
 
+  /// 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 mayHaveSideEffects() const {
+    return mayWriteToMemory() || mayThrow();
+  }
+
   /// Methods for support type inquiry through isa, cast, and dyn_cast:
   static inline bool classof(const Instruction *) { return true; }
   static inline bool classof(const Value *V) {