assembly - MIPS - Branching convention with bne -

in lecture, our professor said there reason behind using bne in branching rather using beq(and left figure out), example shown below.

if ( == j )     i++ ; j-- ; 

which compiles down to

bne  $r1, $r2, l1        # branch if ! ( == j )  addi $r1, $r1, 1         # i++  l1: addi $r2, $r2, -1    # j--  

also, in link, being implied convention in mips assembly implement conditional branching in negation manner. best bet was, keeping common case simple - , therefore fast-, because intuitively if checking equality expect more become equal, , therefore pc branch when not equal. think pushed hard make reasonable, still couldn't distinguish core difference between implementing in beq or in bne. appreciate if explains why.

consider code if had used beq. might end this:

beq $r1, $r2, l1 l2: addi $r2, $r2, -1 # j-- ... ... l1: addi $r1, $r1, 1 #i++ j l2 

or this:

beq $r1, $r2, l1 addi $r2, $r2, -1 # j-- j l2 l1: addi $r1, $r1, 1 #i++ addi $r2, $r2, -1 # j-- l2: 

in either case you'd have branch in 1 of execution paths, compared if had used bne @ beginning.