[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Param ordering; < and <=

This page is part of the web mail archives of SRFI 32 from before July 7th, 2015. The new archives for SRFI 32 contain all messages, not just those from before July 7th, 2015.

> Numerically, op< is less expensive than op<=.  Assuming that a fixnum
> (lambda (x y) (< x y)) compiles to a signed-comparison sequence like
> (x86)
> MOV ax, [esp-4]    ; y
> SUB ax, [esp-8]    ; (< x y)
> JL g01
> MOV ax, BOOLEAN_T  ; #t
> JMP g02
> g01:
> MOV ax, BOOLEAN_F  ; #f
> g02:
> On the x86 and ARM, JL (BLT) tests two flag bits, whereas JLE (BLE)
> tests three.  (For unsigned comparisons, JB (BCC) tests one flag bit,
> whereas JBE (BLS) tests two.)

Do you really think this makes a measurable difference in execution speed?