從C到Assembly jge和jg？

Question

如果語句中的第二個寄存器（例如cmpl％esi， ％edi ）大於或等於（或僅大於）第一個寄存器％esi，則 jg和jge是執行還是跳轉到以下標簽？ 並且結果較大的結果是否存儲在第二個寄存器中，並用於確定跳轉是否執行了連續標簽？

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

[幾乎]每條指令后，CPU都會更新處理器狀態（有時為PS，有時為PSL）寄存器。 CMPL指令執行隱式減法，並更新PS R​​ester的值。 如果執行SUBL指令，將會得到相同的效果，除了SUBL將結果放入目標操作數而CMPL則不然。

Jxx指令根據PS寄存器的值有條件地跳轉。