refactor: optimize number/uint32/base/muldw implementation for better performance#11702
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impawstarlight wants to merge 3 commits intostdlib-js:developfrom
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refactor: optimize number/uint32/base/muldw implementation for better performance#11702impawstarlight wants to merge 3 commits intostdlib-js:developfrom
number/uint32/base/muldw implementation for better performance#11702impawstarlight wants to merge 3 commits intostdlib-js:developfrom
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…`umul`
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The above coverage report was generated for the changes in this PR. |
kgryte
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difficulty: 2
kgryte
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Apr 21, 2026
kgryte
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Apr 21, 2026
| * // returns [ 954437176, 1908874354 ] | ||
| */ | ||
| function umuldw( a, b ) { | ||
| if ( isnan( a ) || isnan( b ) ) { |
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@impawstarlight What is the rationale for keeping these checks here but not in assign.js?
Co-authored-by: Athan <kgryte@gmail.com> Signed-off-by: Athan <kgryte@gmail.com>
kgryte
reviewed
Apr 21, 2026
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| out[ offset ] = ( ( ha*hb ) + w1 + k ) >>> 0; // compute the higher 32 bits and cast to an unsigned 32-bit integer | ||
| out[ offset + stride ] = ( ( t << 16 ) + w3) >>> 0; // compute the lower 32 bits and cast to an unsigned 32-bit integer | ||
| out[ offset + stride ] = umul( a, b ) >>> 0; // compute the lower 32 bits and cast to an unsigned 32-bit integer |
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@impawstarlight I am a bit dense, but how does this manage to produce the same result? Previously, the logic for computing the lower 32 bits doesn't exceed the max uint32, but, here, a*b could, resulting in wraparound, which is a bit counterintuitive to me that it achieves the same result.
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Ultimately, this boils down to a call to imul, but not obvious to me why imul is faster than a bit shift plus addition.
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Description
This pull request:
number/uint32/base/muldwimplementation to improve performance by moving theisnancheck out of the lower level implementation.number/uint32/base/mulfor computing the lower half of the double word product to reduce unnecessary calculation.Related Issues
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