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Correct the C implementation for MultiU16X8toH16

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The comment behind the ASM MultiU16X8toH16 was misleading.
It actually computes ((a<<8)*b)>>16, or (a*b)>>8.

Correct the comment and C reference implementation accordingly.
This commit is contained in:
Yuri D'Elia 2021-07-04 17:03:45 +02:00 committed by DRracer
parent 710852a1f2
commit 31b913cddb
1 changed files with 2 additions and 2 deletions
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4
Firmware/speed_lookuptable.h
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@ -8,7 +8,7 @@ extern const uint16_t speed_lookuptable_slow[256][2] PROGMEM;
#ifndef _NO_ASM
// intRes = intIn1 * intIn2 >> 16
// intRes = intIn1 * intIn2 >> 8
// uses:
// r26 to store 0
// r27 to store the byte 1 of the 24 bit result
@ -82,7 +82,7 @@ asm volatile ( \
static inline void MultiU16X8toH16(uint16_t& intRes, uint8_t& charIn1, uint16_t& intIn2)
{
intRes = ((uint32_t)charIn1 * (uint32_t)intIn2) >> 16;
intRes = ((uint32_t)charIn1 * (uint32_t)intIn2) >> 8;
}
static inline void MultiU24X24toH16(uint16_t& intRes, uint32_t& longIn1, uint32_t& longIn2)