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coord/store: enforce 16 byte alignment for arity 4

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This commit is contained in:
Danny Robson 2016-03-14 22:31:50 +11:00
parent 12b526dff7
commit 039113b661
1 changed files with 47 additions and 6 deletions
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53
coord/store.hpp
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@ -25,7 +25,7 @@
namespace util { namespace coord {
///////////////////////////////////////////////////////////////////////
// Disable GCC warnings about validity of anonyous structures in
// Disable GCC warnings about validity of anonymous structures in
// unions. Push comes to shove I'll manually redsign everything to
// keep this syntax anyway.
#pragma GCC diagnostic push
@ -37,8 +37,21 @@ namespace util { namespace coord {
#endif
///////////////////////////////////////////////////////////////////////////
template <size_t S, typename T, typename...>
struct store {
// Coordinate storage class.
//
// Types of arity multiples of 4 with payloads of at least 16 bytes
// (T >= uint16_t) are guaranteed to be aligned appropriately for SSE (see
// specialisations below).
template <
size_t S,
typename T,
typename...
>
struct
alignas (
sizeof (T) * S % 16 == 0 && sizeof (T) * S >= 16 ? 16 : alignof (T)
)
store {
T data[S];
};
@ -53,8 +66,18 @@ namespace util { namespace coord {
};
};
// Align on 16 bytes if the data is at least 16 bytes long. Prevents tiny
// types like colour4u requiring massive alignments, reduces internal
// fragmentation.
//
// TODO: expand this for other instruction sets. maybe switch on type.
template <typename T>
struct store<4,T,rgba,hsv> {
struct
alignas (
sizeof (T) * 4u >= 16 ? 16 : alignof (T)
)
store<4,T,rgba,hsv> {
union {
T data[4];
struct { T r,g,b,a; };
@ -82,8 +105,17 @@ namespace util { namespace coord {
};
// Align on 16 bytes if the data is at least 16 bytes long. Prevents tiny
// types like colour4u requiring massive alignments, reduces internal
// fragmentation.
//
// TODO: expand this for other instruction sets. maybe switch on type.
template <typename T>
struct store<4,T,xyzw> {
struct
alignas (
sizeof (T) * 4u >= 16 ? 16 : alignof (T)
)
store<4,T,xyzw> {
union {
T data[4];
struct { T x,y,z,w; };
@ -112,8 +144,17 @@ namespace util { namespace coord {
};
// Align on 16 bytes if the data is at least 16 bytes long. Prevents tiny
// types like colour4u requiring massive alignments, reduces internal
// fragmentation.
//
// TODO: expand this for other instruction sets. maybe switch on type.
template <typename T>
struct store<4,T,xyzw,stpq> {
struct
alignas (
sizeof (T) * 4u >= 16 ? 16 : alignof (T)
)
store<4,T,xyzw,stpq> {
union {
T data[4];
struct { T x,y,z,w; };