Suboptimal code generated for _Bool

[Marcin 'Qrczak' Kowalczyk]

W liście z nie, 20-06-2004, godz. 12:14 +0200, Marcin 'Qrczak' Kowalczyk
napisał(a):

> The movzbl is completely unnecessary. It's inserted even if the called
> function is inline.

Another example:

#include <stdbool.h>
static inline bool test1(int x) {return x == 5;}
static inline bool test2(int x) {return test1(x) || x == 10;}
int test3(int x) {return test2(x) ? x : 0;}

Generated code:

test3:
        movl    4(%esp), %eax
        xorl    %edx, %edx
        cmpl    $5, %eax
        je      .L5
        cmpl    $10, %eax
        jne     .L4
        .p2align 4,,7
.L5:
        movl    $1, %edx
.L4:
        testb   %dl, %dl
        jne     .L3
        xorl    %eax, %eax
.L3:
        rep ; ret

BTW, what is the "rep ; ret" in the last line?

If bool is replaced with int, the code is better, but still with
redundant movl's, even with -O2 or -O3:

test3:
        movl    4(%esp), %eax
        cmpl    $5, %eax
        je      .L5
        xorl    %edx, %edx
        cmpl    $10, %eax
        je      .L5
        movl    %edx, %eax
        ret
        .p2align 4,,7
.L5:
        movl    %eax, %edx
        movl    %edx, %eax
        .p2align 4,,2
        ret

-- 
   __("<         Marcin Kowalczyk
   \__/       qrczak@knm.org.pl
    ^^     http://qrnik.knm.org.pl/~qrczak/