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fix(none.h): widen SMLALD/SMLALDX products to 64-bit before summing #320

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fix(none.h): widen SMLALD/SMLALDX products to 64-bit before summing #320

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17 changes: 11 additions & 6 deletions Include/dsp/none.h
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Original file line number Diff line number Diff line change
Expand Up @@ -500,9 +500,13 @@ __STATIC_FORCEINLINE uint32_t __ROR(uint32_t op1, uint32_t op2)
uint64_t sum)
{
/* return (sum + ((q15_t) (x >> 16) * (q15_t) (y >> 16)) + ((q15_t) x * (q15_t) y)); */
return ((uint64_t)(((((q31_t)x << 16) >> 16) * (((q31_t)y << 16) >> 16)) +
((((q31_t)x ) >> 16) * (((q31_t)y ) >> 16)) +
( ((q63_t)sum ) ) ));
/* Both products must be widened to 64-bit before they are summed: with
* both operands left as 32-bit `q31_t`, two same-sign near-full-scale
* products (each up to 2^30) sum to 2^31, which overflows signed 32-bit
* and wraps negative before ever reaching the 64-bit accumulator. */
return ((uint64_t)((q63_t)(((q31_t)x << 16) >> 16) * (((q31_t)y << 16) >> 16) +
(q63_t)(((q31_t)x ) >> 16) * (((q31_t)y ) >> 16) +
( (q63_t)sum ) ));
}


Expand All @@ -515,9 +519,10 @@ __STATIC_FORCEINLINE uint32_t __ROR(uint32_t op1, uint32_t op2)
uint64_t sum)
{
/* return (sum + ((q15_t) (x >> 16) * (q15_t) y)) + ((q15_t) x * (q15_t) (y >> 16)); */
return ((uint64_t)(((((q31_t)x << 16) >> 16) * (((q31_t)y ) >> 16)) +
((((q31_t)x ) >> 16) * (((q31_t)y << 16) >> 16)) +
( ((q63_t)sum ) ) ));
/* See __SMLALD above: widen to 64-bit before summing the two products. */
return ((uint64_t)((q63_t)(((q31_t)x << 16) >> 16) * (((q31_t)y ) >> 16) +
(q63_t)(((q31_t)x ) >> 16) * (((q31_t)y << 16) >> 16) +
( (q63_t)sum ) ));
}


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