[InstSimpify] Add tests for simplify select with X & Y == -1 cond; NFC

Author: goldsteinn

llvm/test/Transforms/InstCombine/select.ll

@@ -4837,3 +4837,19 @@ define i32 @replace_and_cond_multiuse2(i1 %cond1, i1 %cond2) {
   %mux = select i1 %cond1, i32 %sel, i32 1
   ret i32 %mux
 }
+
+define i32 @src_simplify_2x_at_once_and(i32 %x, i32 %y) {
+; CHECK-LABEL: @src_simplify_2x_at_once_and(
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[AND0:%.*]] = icmp eq i32 [[AND]], -1
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[COND:%.*]] = select i1 [[AND0]], i32 0, i32 [[XOR]]
+; CHECK-NEXT:    ret i32 [[COND]]
+;
+  %and = and i32 %x, %y
+  %and0 = icmp eq i32 %and, -1
+  %sub = sub i32 %x, %y
+  %xor = xor i32 %x, %y
+  %cond = select i1 %and0, i32 %sub, i32 %xor
+  ret i32 %cond
+}