[LLVMdev] built-in longjmp and setjmp

[Akira Hatanaka]

I declared gi2 as "volatile" and I think gi2 is still incremented once.
Here is a snippet of the code. Line 39 - 42 increments gi2.

According to the standard, shouldn't ++gi2 be executed twice regardless of
whether gi2 is volatile or not? Isn't the missing chain from EH_SJLJ_SETJMP
node to load/store nodes that access gi2 causing this problem (please see
attached file in my previous email)?

# line 39 - 47
 ldr r1, LCPI1_1
 ldr r2, [r1]
 add r2, r2, #1
 str r2, [r1]
 add r4, pc, #8              @ eh_setjmp begin
 str r4, [r0, #4]
 mov r0, #0
 add pc, pc, #0
 mov r0, #1                  @ eh_setjmp end

 ...
LCPI1_1:
  .long _gi2
  .align  2


On Wed, Apr 27, 2011 at 11:38 AM, Akira Hatanaka <ahatanak at gmail.com> wrote:

> I have another basic question about setjmp/longjmp.
>
> When I compile and run the following program, is it expected that global
> variable gi2 will be incremented twice? It seems that the code generated
> with clang and llc increments it only once (line 37-43 of attached file).
>
> $ clang setjmp6.c -o setjmp6.arm.ll -emit-llvm -O3 -S -ccc-host-triple
> arm-unknown-darwin -ccc-clang-archs arm
> $ llc setjmp6.arm.ll -o setjmp6.arm.s
>
>
> #include <stdio.h>
> #include <stdlib.h>
> void *buf[20];
>
> int gi2 = 0;
>
>
> void __attribute__ ((noinline)) sub2 (void)
> {
>   __builtin_longjmp (buf, 1);
>
> }
>
> int
> main (int argc, char **argv)
> {
>   int n = atoi (argv[1]);
>   int r = __builtin_setjmp (buf);
>   ++gi2;
>
>   if (r)
>     {
>       printf ("setjmp %d\n", n + gi2);
>       return 0;
>     }
>
>   sub2 ();
>
>   return 0;
> }
>
>
> On Wed, Apr 13, 2011 at 10:05 AM, Jakob Stoklund Olesen <stoklund at 2pi.dk>wrote:
>
>>
>> On Apr 13, 2011, at 9:51 AM, Akira Hatanaka wrote:
>>
>> > int
>> > main (int argc, char** argv)
>> > {
>> >   int n = atoi(argv[1]), r;
>> >
>> >   if ((r = setjmp (buf)))
>> >     {
>> >       printf("n = %d\n", n);
>> >       return 0;
>> >     }
>>
>>
>> /jakob
>>
>>
>
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