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| Why does CQO instruction not recognized by PB https://www.purebasic.fr/english/viewtopic.php?f=35&t=72198 |
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| Author: | Jeff88 [ Sat Feb 02, 2019 12:26 am ] |
| Post subject: | Why does CQO instruction not recognized by PB |
I wanted to see the timing difference between IDIV and DIV. So I wrote a simple program, looked at the assembly code and cut and pasted the portion for c=a/b into the timing loop. I changed IDIV to DIV. The compiler gave a syntax error for CQO line. I put a ! in front of the CQO to send directly to FASM and it worked fine. Any comments? Truly amazing how fast cpu's are today. Code: ntimes=1e6
a=999999999999999999 b=567890123456789 atime=ElapsedMilliseconds() For i=1 To ntimes Next btime=ElapsedMilliseconds() For i=1 To ntimes c=a/b Next c=0 ctime=ElapsedMilliseconds() For i=1 To ntimes ;c=a/b EnableASM MOV r15,qword [v_a] PUSH qword [v_b] MOV rax,r15 POP rcx !CQO ;trouble spot DIV rcx MOV r15,rax MOV qword [v_c],r15 DisableASM Next dtime=ElapsedMilliseconds() OpenConsole() PrintN("nsec/loop") PrintN(Str(btime-atime)+" "+Str(ctime-btime)+" "+Str(dtime-ctime)) PrintN(Str(a/b)+ " "+Str(c)) Input() End |
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| Author: | luis [ Sat Feb 02, 2019 12:47 am ] |
| Post subject: | Re: Why does CQO instruction not recognized by PB |
I'm just guessing here. I think PB EnableASM supports only the opcodes up to 80486, and CQO was introduced with x64. You have compiled your PB program on x64 so you found that instruction in the generated code. |
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