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Use offsetof to ensure MMX union packing is as expected

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Jonathan Campbell
2021-11-23 13:52:21 -08:00
parent b8ef06d410
commit affa499ce9
1 changed files with 7 additions and 1 deletions
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8
include/mmx.h
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@@ -21,6 +21,8 @@
#if C_FPU #if C_FPU
#include <stddef.h>
typedef union { typedef union {
uint64_t q; uint64_t q;
@@ -36,13 +38,17 @@ typedef union {
} sd; } sd;
static_assert(sizeof(sd) == 8, "MMX packing error"); static_assert(sizeof(sd) == 8, "MMX packing error");
struct { struct uw_t {
uint16_t w0,w1,w2,w3; uint16_t w0,w1,w2,w3;
} uw; } uw;
static_assert(sizeof(uw) == 8, "MMX packing error"); static_assert(sizeof(uw) == 8, "MMX packing error");
uint16_t uwa[4]; /* for PSHUFW */ uint16_t uwa[4]; /* for PSHUFW */
static_assert(sizeof(uwa) == 8, "MMX packing error"); static_assert(sizeof(uwa) == 8, "MMX packing error");
static_assert(offsetof(uw_t,w0) == 0, "MMX packing error");
static_assert(offsetof(uw_t,w1) == 2, "MMX packing error");
static_assert(offsetof(uw_t,w2) == 4, "MMX packing error");
static_assert(offsetof(uw_t,w3) == 6, "MMX packing error");
struct { struct {
int16_t w0,w1,w2,w3; int16_t w0,w1,w2,w3;