Implement (A&((~A)|B)) -> A&B transformation in the instruction combiner. This

takes care of all permutations of this pattern.

llvm-svn: 60290

2 files changed, 19 insertions, 10 deletions

diff --git a/llvm/lib/Target/README.txt b/llvm/lib/Target/README.txt
index b0d93f0264a..bf7c0b14475 100644
--- a/llvm/lib/Target/README.txt
+++ b/llvm/lib/Target/README.txt
@@ -1086,16 +1086,6 @@ produces better code on X86.
 
 //===---------------------------------------------------------------------===//
 
-From GCC Bug 33512:
-int f(int y, int x)
-{
- return x & ((~x) | y);
-}
-Should combine to x & y.  Currently not optimized with "clang
--emit-llvm-bc | opt -std-compile-opts".
-
-//===---------------------------------------------------------------------===//
-
 From GCC Bug 15784:
 #define abs(x) x>0?x:-x
 int f(int x, int y)
diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
index 8716e9a8a6c..ace3ff80d4f 100644
--- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -3993,6 +3993,7 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
         std::swap(Op0, Op1);
       }
     }
+
     if (Op1->hasOneUse() &&
         match(Op1, m_Xor(m_Value(A), m_Value(B)))) {
       if (B == Op0) {                                // B&(A^B) -> B&(B^A)
@@ -4005,6 +4006,24 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
         return BinaryOperator::CreateAnd(A, NotB);
       }
     }
+
+    // (A&((~A)|B)) -> A&B
+    if (match(Op0, m_Or(m_Not(m_Value(A)), m_Value(B)))) {
+      if (A == Op1)
+        return BinaryOperator::CreateAnd(A, B);
+    }
+    if (match(Op0, m_Or(m_Value(A), m_Not(m_Value(B))))) {
+      if (B == Op1)
+        return BinaryOperator::CreateAnd(A, B);
+    }
+    if (match(Op1, m_Or(m_Not(m_Value(A)), m_Value(B)))) {
+      if (A == Op0)
+        return BinaryOperator::CreateAnd(A, B);
+    }
+    if (match(Op1, m_Or(m_Value(A), m_Not(m_Value(B))))) {
+      if (B == Op0)
+        return BinaryOperator::CreateAnd(A, B);
+    }
   }
   
   if (ICmpInst *RHS = dyn_cast<ICmpInst>(Op1)) {