Teach InstructionSimplify to fold (A & B) & A -> A & B and (A | B) | A -> A | B.

Reassociate does this but it doesn't catch all cases (e.g. if the operands are i1).

llvm-svn: 113651

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 24cd3433a2c..b49b4d0c6ab 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -106,6 +106,16 @@ Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD) {
       (A == Op0 || B == Op0))
     return Op0;
   
+  // (A & B) & A -> A & B
+  if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
+      (A == Op1 || B == Op1))
+    return Op0;
+
+  // A & (A & B) -> A & B
+  if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
+      (A == Op0 || B == Op0))
+    return Op1;
+
   return 0;
 }
 
@@ -165,6 +175,16 @@ Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD) {
       (A == Op0 || B == Op0))
     return Op0;
   
+  // (A | B) | A -> A | B
+  if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
+      (A == Op1 || B == Op1))
+    return Op0;
+
+  // A | (A | B) -> A | B
+  if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
+      (A == Op0 || B == Op0))
+    return Op1;
+
   return 0;
 }