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added mulhu CRT routines #645

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added mulhu CRT routines #645

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@ZERICO2005 ZERICO2005 commented Sep 30, 2025 •
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Added multiply high unsigned routines. These can be used to optimize division by a constant. __smulhu is optimized, but the rest are not well optimized. They use the exact same calling convention as the regular multiplication routines. __bmulhu was not added since it is just mlt bc \ ld a, b.

__smulhu   :         HL = ((uint32_t)         HL * (uint32_t)      BC) >> 16
__imulhu   :        UHL = ((uint48_t)        UHL * (uint48_t)     UBC) >> 24
__lmulhu   :      E:UHL = ((uint64_t)      E:UHL * (uint64_t)   A:UBC) >> 32
__i48mulhu :    UDE:UHL = ((uint96_t)    UDE:UHL * (uint96_t) UIY:UBC) >> 48
__llmulhu  : BC:UDE:UHL = ((uint128_t)BC:UDE:UHL * (uint128_t) (SP64)) >> 64

__smulhu   :  32 bytes |  33F +  12R +   9W +  17
__imulhu   : 117 bytes | 118F +  39R +  38W +  37
__lmulhu   : 1 call to __llmulu
__i48mulhu :  88 bytes | 897F + 243R + 179W + 343
__llmulhu  : 4 calls to __llmulu

@ZERICO2005 ZERICO2005 marked this pull request as draft September 30, 2025 03:02
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