translate-c: Add support for vector expressions

Includes vector types, __builtin_shufflevector, and __builtin_convertvector

1 files changed, 32 insertions, 0 deletions

diff --git a/lib/std/meta.zig b/lib/std/meta.zig
index cdc93e5d33..2ed737cea3 100644
--- a/lib/std/meta.zig
+++ b/lib/std/meta.zig
@@ -1297,3 +1297,35 @@ pub fn globalOption(comptime name: []const u8, comptime T: type) ?T {
         return null;
     return @as(T, @field(root, name));
 }
+
+/// This function is for translate-c and is not intended for general use.
+/// Convert from clang __builtin_shufflevector index to Zig @shuffle index
+/// clang requires __builtin_shufflevector index arguments to be integer constants.
+/// negative values for `this_index` indicate "don't care" so we arbitrarily choose 0
+/// clang enforces that `this_index` is less than the total number of vector elements
+/// See https://ziglang.org/documentation/master/#shuffle
+/// See https://clang.llvm.org/docs/LanguageExtensions.html#langext-builtin-shufflevector
+pub fn shuffleVectorIndex(comptime this_index: c_int, comptime source_vector_len: usize) i32 {
+    if (this_index <= 0) return 0;
+
+    const positive_index = @intCast(usize, this_index);
+    if (positive_index < source_vector_len) return @intCast(i32, this_index);
+    const b_index = positive_index - source_vector_len;
+    return ~@intCast(i32, b_index);
+}
+
+test "shuffleVectorIndex" {
+    const vector_len: usize = 4;
+
+    testing.expect(shuffleVectorIndex(-1, vector_len) == 0);
+
+    testing.expect(shuffleVectorIndex(0, vector_len) == 0);
+    testing.expect(shuffleVectorIndex(1, vector_len) == 1);
+    testing.expect(shuffleVectorIndex(2, vector_len) == 2);
+    testing.expect(shuffleVectorIndex(3, vector_len) == 3);
+
+    testing.expect(shuffleVectorIndex(4, vector_len) == -1);
+    testing.expect(shuffleVectorIndex(5, vector_len) == -2);
+    testing.expect(shuffleVectorIndex(6, vector_len) == -3);
+    testing.expect(shuffleVectorIndex(7, vector_len) == -4);
+}
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