From C to Assembly jge and jg?

Question

Does jg and jge execute or jump to the following label if the second register in the statement eg., cmpl %esi, %edi is greater than or equal to (or only greater than) the first register %esi ? And is the result of which one is greater stored in the second register and used to determine if jump executes the consecutive label?

sum1.c

 int sum(int first, int last)
 {
      int sum = 0;
      int in_between;
      for (in_between = first; in_between <= last; in_between++)
      {
           sum += in_between;
      }
      return sum;
 }

sum1.s:

    .file   "sum1.c"
    .text
.globl sum
    .type   sum, @function
sum:
.LFB0:
    .cfi_startproc
    movl    %edi, %edx ; puts first into in_between
    movl    $0, %eax ; sets sum to zero
    cmpl    %esi, %edi ;compares first and last, checking if first– last < 0
    jg      .L3 ; jumps to .L3 if first is greater than last, otherwise 
 ;executes .L6
.L6:
    addl    %edx, %eax ;adds in_between to sum
    addl    $1, %edx ; increments in_between
    cmpl    %edx, %esi ; makes the comparison between in_between and last, 
    ;last < in_between
    jge     .L6 ; jumps to .L6 if last is greater than or equal to 
    ;in_between. (the result jump uses is stored in last).    
.L3:
    rep
    ret ;returns the value stored in %eax register.
    .cfi_endproc
.LFE0:
    .size   sum, .-sum
    .ident  "GCC: (GNU) 4.4.7 20120313 (Red Hat 4.4.7-17)"
    .section        .note.GNU-stack,"",@progbits

Answer 1

The CPU updates the processor status (PS sometimes PSL) register after [nearly] every instruction. The CMPL instruction does an implicit subtraction and updates the values of the PS rester. You'd get the same effect if you did a SUBL instruction, except that SUBL puts the result in the destination operand while CMPL does not.

The Jxx instructions conditionally branch depending upon the value of the PS register.