Support i64.mul_wide_s and i64.mul_wide_u from Wide Arithmetic proposal#8652
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Support i64.mul_wide_s and i64.mul_wide_u from Wide Arithmetic proposal#8652stevenfontanella wants to merge 3 commits intomainfrom
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MaxGraey
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tlively
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| uint64_t highOfLow = (lowLow >> 32) + lowHigh; | ||
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| // We might have a carry into the next 32 (the low of the high), mask it out | ||
| // now so we can add highLow. | ||
| uint64_t carry = highOfLow >> 32; | ||
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| // This is also guaranteed to not overflow by the same logic. | ||
| highOfLow = (highOfLow & 0xffffffff) + highLow; | ||
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| // highOfLow might have exceeded 32 bits again, carry it again | ||
| uint64_t carry2 = highOfLow >> 32; |
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Why do we calculate carry and carry2 separately? It seems that if we started with highOfLow = (lowLow >> 32) + lowHigh + highLow, then we could just calculate a single combined carry. Does that open us up to overflow problems?
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Part of #8544. Unit tests were written by Gemini and double-checked against python with this script.
TODO: Move the existing 128 add/sub logic from the interpreter into int128.h.