44fe90d0b3
Most (all?) processors that Go supports supply a hardware instruction that takes a byte and returns the number of zeros trailing the first 1 encountered, or 8 if no ones are found. This is the index within the byte of the first 1 encountered. CTZ should improve the performance of the nextFreeIndex function. Since nextFreeIndex wants the next unmarked (0) bit a bit-wise complement is needed before calling ctz. Furthermore unmarked bits associated with previously allocated objects need to be ignored. Instead of writing a 1 as we allocate the code masks all bits less than the freeindex after loading the byte. While this CL does not actual execute a CTZ instruction it supplies a ctz function with the appropiate signature along with the logic to execute it. Change-Id: I5c55ce0ed48ca22c21c4dd9f969b0819b4eadaa7 Reviewed-on: https://go-review.googlesource.com/20169 Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Austin Clements <austin@google.com> |
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The Go Programming Language
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Binary Distribution Notes
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