4.49

it’s a brilliant idea, 3 xor is a normal swap

if x = 9, y = 10

x = x ^ y  x:9^10; y:10
y = x ^ y  x:9^10; y:9
x = x ^ y  x:10; y:9

if change y after step 1

tmp = x    x:9; y:10; tmp:9  # store x
x = x ^ y  x:9^10; y:10
y = tmp    x:9^10; y:9       # set y to origin x
y = x ^ y  x:9^10; y:10
x = x ^ y  x:9; y:10

no swap happens. that’s core in code below

!INCLUDE "./code/bubble-sort/bubble-sort-pointer-1-cmove.ys"

test and output, watch memory changes:

../sim/misc/yas bubble-sort-pointer-1-cmove.ys
../sim/misc/yis bubble-sort-pointer-1-cmove.yo
Stopped in 141 steps at PC = 0x13.  Status 'HLT', CC Z=1 S=0 O=0
Changes to registers:
%rax:    0x0000000000000000    0x0000000000000020
%rsp:    0x0000000000000000    0x0000000000000200
%rsi:    0x0000000000000000    0x0000000000000018
%rdi:    0x0000000000000000    0x0000000000000018
%r9:    0x0000000000000000    0x0000000000000002
%r10:    0x0000000000000000    0x0000000000000001
%r11:    0x0000000000000000    0x0000000000000002
Changes to memory:
0x0018:    0x0000000000000004    0x0000000000000001
0x0020:    0x0000000000000003    0x0000000000000002
0x0028:    0x0000000000000002    0x0000000000000003
0x0030:    0x0000000000000001    0x0000000000000004