(A & sext(C)) | (B & ~sext(C) -> C ? A : B

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58351 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 39 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 8ec775b0c3..4ec36ad151 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -4337,6 +4337,25 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
         return BinaryOperator::CreateAnd(V1, Or);
       }
     }
+
+    // (A & sext(C0)) | (B & ~sext(C0) ->  C0 ? A : B
+    if (isa<SExtInst>(C) &&
+        cast<User>(C)->getOperand(0)->getType() == Type::Int1Ty) {
+      if (match(D, m_Not(m_Value(C))))
+        return SelectInst::Create(cast<User>(C)->getOperand(0), A, B);
+      // And commutes, try both ways.
+      if (match(B, m_Not(m_Value(C))))
+        return SelectInst::Create(cast<User>(C)->getOperand(0), A, D);
+    }
+    // Or commutes, try both ways.
+    if (isa<SExtInst>(D) &&
+        cast<User>(D)->getOperand(0)->getType() == Type::Int1Ty) {
+      if (match(C, m_Not(m_Value(D))))
+        return SelectInst::Create(cast<User>(D)->getOperand(0), A, B);
+      // And commutes, try both ways.
+      if (match(A, m_Not(m_Value(D))))
+        return SelectInst::Create(cast<User>(D)->getOperand(0), C, B);
+    }
   }
   
   // (X >> Z) | (Y >> Z)  -> (X|Y) >> Z  for all shifts.
diff --git a/test/Transforms/InstCombine/logical-select.ll b/test/Transforms/InstCombine/logical-select.ll
new file mode 100644
index 0000000000..6369badee6
--- /dev/null
+++ b/test/Transforms/InstCombine/logical-select.ll
@@ -0,0 +1,20 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep select | count 2
+
+define i32 @foo(i32 %a, i32 %b, i32 %c, i32 %d) nounwind {
+  %e = icmp slt i32 %a, %b
+  %f = sext i1 %e to i32
+  %g = and i32 %c, %f
+  %h = xor i32 %f, -1
+  %i = and i32 %d, %h
+  %j = or i32 %g, %i
+  ret i32 %j
+}
+define i32 @bar(i32 %a, i32 %b, i32 %c, i32 %d) nounwind {
+  %e = icmp slt i32 %a, %b
+  %f = sext i1 %e to i32
+  %g = and i32 %c, %f
+  %h = xor i32 %f, -1
+  %i = and i32 %d, %h
+  %j = or i32 %i, %g
+  ret i32 %j
+}