jumper, split store_f16 into to_half, store4

Pretty much the same deal as the last CL going the other direction:
split store_f16 into to_half() and store4().  Platforms that had fused
strategies here get a little less optimal, but the code's easier to
follow, maintain, and reuse.

Also adds widen_cast() to encapsulate the fairly common pattern of
expanding one of our logical vector types (e.g. 8-byte U16) up to the
width of the physical vector type (e.g. 16-byte __m128i).  This
operation is deeply understood by Clang, and often is a no-op.

I could make bit_cast() do this, but it seems clearer to have two names.

Change-Id: I7ba5bb4746acfcaa6d486379f67e07baee3820b2
Reviewed-on: https://skia-review.googlesource.com/11204
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/jumper/SkJumper_misc.h b/src/jumper/SkJumper_misc.h
index 96035bd084..54e957ad6e 100644
--- a/src/jumper/SkJumper_misc.h
+++ b/src/jumper/SkJumper_misc.h
@@ -28,6 +28,14 @@ SI Dst bit_cast(const Src& src) {
     return unaligned_load<Dst>(&src);
 }
 
+template <typename Dst, typename Src>
+SI Dst widen_cast(const Src& src) {
+    static_assert(sizeof(Dst) > sizeof(Src), "");
+    Dst dst;
+    memcpy(&dst, &src, sizeof(Src));
+    return dst;
+}
+
 // A couple functions for embedding constants directly into code,
 // so that no .const or .literal4 section is created.
 SI int C(int x) {