Improved halide_popcount #7225
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Improved halide_popcount #7225
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| @@ -155,8 +155,9 @@ template<typename T> | |||
| inline int halide_popcount(T a) { | |||
| int bits_set = 0; | |||
| while (a != 0) { | |||
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FWIW, ~all modern compilers should have popcount as an intrinsic -- see popcount64 in Util.cpp, maybe we should just adapt that here
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What's the story on this, ready to land? |
vksnk
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Jan 24, 2023
| @@ -152,15 +152,39 @@ inline float float_from_bits(uint32_t bits) { | |||
| } | |||
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| template<typename T> | |||
| inline int halide_popcount(T a) { | |||
| inline int halide_popcount_fallback(T a) { | |||
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I would leave a link to the source for this algorithm for the reference (found this one https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan, for example).
src/CodeGen_C.cpp
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| bits_set += a & 1; | ||
| a >>= 1; | ||
| bits_set += 1; | ||
| // NOTE(aelphy): remove least significant zeros and the first met one |
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I would just make it a regular comment (i.e. remove NOTE(aelphy) part).
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Where does this PR stand? |
ardier
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Mar 3, 2024
* Improved halide_popcount * reused popcount64 from Utils.cpp in CodeGen_C * Fixed comment for popcount
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This is a slightly more efficient version of a popcount, which has as many iterations as many ones are in the binary representation.