When linearizing a multiplication, return at once if we see a factor of zero,

since then the entire expression must equal zero (similarly for other operations
with an absorbing element).  With this in place a bunch of reassociate code for
handling constants is dead since it is all taken care of when linearizing.  No
intended functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158398 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 1 deletions

diff --git a/include/llvm/Constants.h b/include/llvm/Constants.h
index a3f5b95dbc..fdd53823aa 100644
--- a/include/llvm/Constants.h
+++ b/include/llvm/Constants.h
@@ -919,9 +919,15 @@ public:
 
   /// getBinOpIdentity - Return the identity for the given binary operation,
   /// i.e. a constant C such that X op C = X and C op X = X for every X.  It
-  /// is an error to call this for an operation that doesn't have an identity.
+  /// returns null if the operator doesn't have an identity.
   static Constant *getBinOpIdentity(unsigned Opcode, Type *Ty);
 
+  /// getBinOpAbsorber - Return the absorbing element for the given binary
+  /// operation, i.e. a constant C such that X op C = C and C op X = C for
+  /// every X.  For example, this returns zero for integer multiplication.
+  /// It returns null if the operator doesn't have an absorbing element.
+  static Constant *getBinOpAbsorber(unsigned Opcode, Type *Ty);
+
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Constant);