C++: Support __builtin_shuffle builtin

While here write gcc instead of GNU, which is more accurate.

cpp/ql/lib/semmle/code/cpp/exprs/BuiltInOperations.qll

@@ -121,7 +121,7 @@ class BuiltInNoOp extends BuiltInOperation, @noopexpr {
 /**
  * A C/C++ `__builtin_offsetof` built-in operation (used by some implementations
  * of `offsetof`).  The operation retains its semantics even in the presence
- * of an overloaded `operator &`).  This is a GNU/Clang extension.
+ * of an overloaded `operator &`).  This is a gcc/clang extension.
  * ```
  * struct S {
  *   int a, b;
@@ -494,6 +494,23 @@ class BuiltInOperationBuiltInShuffleVector extends BuiltInOperation, @builtinshu
   override string getAPrimaryQlClass() { result = "BuiltInOperationBuiltInShuffleVector" }
 }
 
+/**
+ * A gcc `__builtin_shuffle` expression.
+ *
+ * It outputs a permutation of elements from one or two input vectors.
+ * Please see https://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html
+ * for more information.
+ * ```
+ * // Concatenate every other element of 4-element vectors V1 and V2.
+ * V3 = __builtin_shufflevector(V1, V2, {0, 2, 4, 6});
+ * ```
+ */
+class BuiltInOperationBuiltInShuffle extends BuiltInOperation, @builtinshuffle {
+  override string toString() { result = "__builtin_shuffle" }
+
+  override string getAPrimaryQlClass() { result = "BuiltInOperationBuiltInShuffle" }
+}
+
 /**
  * A clang `__builtin_convertvector` expression.
  *
@@ -946,7 +963,7 @@ class BuiltInOperationIsFinal extends BuiltInOperation, @isfinalexpr {
 }
 
 /**
- * The `__builtin_choose_expr` expression.  This is a GNU/Clang extension.
+ * The `__builtin_choose_expr` expression.  This is a gcc/clang extension.
  *
  * The expression functions similarly to the ternary `?:` operator, except
  * that it is evaluated at compile-time.

cpp/ql/lib/semmlecode.cpp.dbscheme

@@ -1654,6 +1654,7 @@ case @expr.kind of
 | 331 = @isaggregate
 | 332 = @hasuniqueobjectrepresentations
 | 333 = @builtinbitcast
+| 334 = @builtinshuffle
 ;
 
 @var_args_expr = @vastartexpr
@@ -1719,6 +1720,7 @@ case @expr.kind of
             | @isaggregate
             | @hasuniqueobjectrepresentations
             | @builtinbitcast
+            | @builtinshuffle
             ;
 
 new_allocated_type(

cpp/ql/test/library-tests/vector_types/builtin_ops.expected

@@ -1,2 +1,4 @@
+| vector_types2.cpp:10:15:10:42 | __builtin_shuffle |
+| vector_types2.cpp:11:15:11:45 | __builtin_shuffle |
 | vector_types.cpp:31:13:31:49 | __builtin_shufflevector |
 | vector_types.cpp:58:10:58:52 | __builtin_convertvector |

cpp/ql/test/library-tests/vector_types/variables.expected

@@ -13,6 +13,12 @@
 | file://:0:0:0:0 | gp_offset | gp_offset | file://:0:0:0:0 | unsigned int | 4 |
 | file://:0:0:0:0 | overflow_arg_area | overflow_arg_area | file://:0:0:0:0 | void * | 8 |
 | file://:0:0:0:0 | reg_save_area | reg_save_area | file://:0:0:0:0 | void * | 8 |
+| vector_types2.cpp:5:7:5:7 | a | a | vector_types2.cpp:2:13:2:15 | v4i | 16 |
+| vector_types2.cpp:6:7:6:7 | b | b | vector_types2.cpp:2:13:2:15 | v4i | 16 |
+| vector_types2.cpp:7:7:7:12 | mask_1 | mask_1 | vector_types2.cpp:2:13:2:15 | v4i | 16 |
+| vector_types2.cpp:8:7:8:12 | mask_2 | mask_2 | vector_types2.cpp:2:13:2:15 | v4i | 16 |
+| vector_types2.cpp:10:7:10:11 | res_1 | res_1 | vector_types2.cpp:2:13:2:15 | v4i | 16 |
+| vector_types2.cpp:11:7:11:11 | res_2 | res_2 | vector_types2.cpp:2:13:2:15 | v4i | 16 |
 | vector_types.cpp:9:21:9:21 | x | x | vector_types.cpp:6:15:6:17 | v4f | 16 |
 | vector_types.cpp:14:18:14:20 | lhs | lhs | vector_types.cpp:6:15:6:17 | v4f | 16 |
 | vector_types.cpp:14:27:14:29 | rhs | rhs | vector_types.cpp:6:15:6:17 | v4f | 16 |

cpp/ql/test/library-tests/vector_types/vector_types2.cpp

@@ -0,0 +1,12 @@
+// semmle-extractor-options: --gnu --gnu_version 80000
+typedef int v4i __attribute__((vector_size (16)));
+
+void f() {
+  v4i a = {1,2,3,4};
+  v4i b = {5,6,7,8};
+  v4i mask_1 = {3,0,1,2};
+  v4i mask_2 = {3,5,4,2};
+
+  v4i res_1 = __builtin_shuffle(a, mask_1);
+  v4i res_2 = __builtin_shuffle(a, b, mask_2);
+}