PNaCl SIMD documentation: fix vector-scalar examples, currently unsupported by LLVM

native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst

Index: native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst
diff --git a/native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst b/native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst
index 3bece15a604112ad7c03177c38828e8d686e47ab..337a962bc192bea08577afccb493760b5f3a6a7b 100644
--- a/native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst
+++ b/native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst
@@ -232,9 +232,8 @@ Vector types can be used through the ``vector_size`` attribute:
   v4s a = {1,2,3,4};
   v4s b = {5,6,7,8};
   v4s c, d, e;
-  c = b + 1;  /* c = b + {1,1,1,1}; */
-  d = 2 * b;  /* d = {2,2,2,2} * b; */
-  e = c + d;
+  c = a + b;  /* c = {6,8,10,12} */
+  d = b >> a; /* d = {2,1,0,0} */
 
 Vector comparisons are represented as a bitmask as wide as the compared
 elements of all ``0`` or all ``1``:
@@ -335,21 +334,32 @@ to the number of indices specified.
   // identity operation - return 4-element vector v1.
   __builtin_shufflevector(v1, v1, 0, 1, 2, 3)
 
-  // "Splat" element 0 of V1 into a 4-element result.
-  __builtin_shufflevector(V1, V1, 0, 0, 0, 0)
+  // "Splat" element 0 of v1 into a 4-element result.
+  __builtin_shufflevector(v1, v1, 0, 0, 0, 0)
 
-  // Reverse 4-element vector V1.
-  __builtin_shufflevector(V1, V1, 3, 2, 1, 0)
+  // Reverse 4-element vector v1.
+  __builtin_shufflevector(v1, v1, 3, 2, 1, 0)
 
-  // Concatenate every other element of 4-element vectors V1 and V2.
-  __builtin_shufflevector(V1, V2, 0, 2, 4, 6)
+  // Concatenate every other element of 4-element vectors v1 and v2.
+  __builtin_shufflevector(v1, v2, 0, 2, 4, 6)
 
-  // Concatenate every other element of 8-element vectors V1 and V2.
-  __builtin_shufflevector(V1, V2, 0, 2, 4, 6, 8, 10, 12, 14)
+  // Concatenate every other element of 8-element vectors v1 and v2.
+  __builtin_shufflevector(v1, v2, 0, 2, 4, 6, 8, 10, 12, 14)
 
   // Shuffle v1 with some elements being undefined
   __builtin_shufflevector(v1, v1, 3, -1, 1, -1)
 
+One common use of ``__builtin_shufflevector`` is to perform
+vector-scalar operations:
+
+.. naclcode::
+
+  typedef int v4s __attribute__((vector_size(16)));
+  v4s shift_right_by(v4s shift_me, int shift_amount) {
+    v4s tmp = {shift_amount};
+    return shift_me >> __builtin_shuffle_vector(tmp, tmp, 0, 0, 0, 0);
+  }
+
 Auto-Vectorization
 ------------------