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Work around UBSan unaligned access errors.

The underlying objects are all 8-bit integers.
Verified that the generated assembly still just uses MOVD.

Signed-off-by: Jean-Marc Valin <jmvalin@jmvalin.ca>

--- a/celt/x86/x86cpu.h

+++ b/celt/x86/x86cpu.h

@@ -56,8 +56,16 @@

 int opus_select_arch(void);

 # endif

+/*MOVD should not impose any alignment restrictions, but the C standard does,

+   and UBSan will report errors if we actually make unaligned accesses.

+  Use this to work around those restrictions (which should hopefully all get

+   optimized to a single MOVD instruction).*/

+#define OP_LOADU_EPI32(x) \

+  (int)((*(unsigned char *)(x) | *((unsigned char *)(x) + 1) << 8U |\

+   *((unsigned char *)(x) + 2) << 16U | (opus_uint32)*((unsigned char *)(x) + 3) << 24U))

+

 #define OP_CVTEPI8_EPI32_M32(x) \

- (_mm_cvtepi8_epi32(_mm_cvtsi32_si128(*(int *)(x))))

+ (_mm_cvtepi8_epi32(_mm_cvtsi32_si128(OP_LOADU_EPI32(x))))

 #define OP_CVTEPI16_EPI32_M64(x) \

  (_mm_cvtepi16_epi32(_mm_loadl_epi64((__m128i *)(x))))