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Re: Hitachi djprobe mechanism


hi,

I was interested enough that I hacked together the attached patch (I used gcc svn HEAD and binutils cvs HEAD). It seems to work nicely with -O0 but it seems to break on the simple testcase below with -O2/-O3 on x86. i.e., it reports a bb boundary at 0x11 and I cannot see why there would be a bb boundary there.

Also, I noticed that if you want to use this code for djprobe insertion location verification, you will need to parse the resulting binary anyway to detect the call sites which are not really bb boundaries and are thus not reported by the patch as bb boundaries but which are forbidden boundary locations for djprobe insertion.

I will do a lot more testing in a few days but I thought it might be useful to send an early report.

regards,
Mathieu

#include <stdio.h>
static int foo (void)
{
       if (3) {
               int i = 0;
               while (i < 100) {
                       printf ("test\n");
                       i++;
               }
       }
       return 8;
}

int main (int argc, char *argv[])
{
       foo ();
       return 0;
}

Here, I get the following list of basic blocks with the debugging information:
ad: 0x0
ad: 0x11
ad: 0x20
ad: 0x32
while the assembly output does not seem to contain any jump to 0x11:
00000000 <main>:
0: 8d 4c 24 04 lea 0x4(%esp),%ecx
4: 83 e4 f0 and $0xfffffff0,%esp
7: ff 71 fc pushl 0xfffffffc(%ecx)
a: 55 push %ebp
b: 89 e5 mov %esp,%ebp
d: 53 push %ebx
e: 31 db xor %ebx,%ebx
10: 51 push %ecx
11: 83 ec 10 sub $0x10,%esp
14: 8d b6 00 00 00 00 lea 0x0(%esi),%esi
1a: 8d bf 00 00 00 00 lea 0x0(%edi),%edi
20: c7 04 24 00 00 00 00 movl $0x0,(%esp)
27: 43 inc %ebx
28: e8 fc ff ff ff call 29 <main+0x29>
2d: 83 fb 64 cmp $0x64,%ebx
30: 75 ee jne 20 <main+0x20>
32: 83 c4 10 add $0x10,%esp
35: 31 c0 xor %eax,%eax
37: 59 pop %ecx
38: 5b pop %ebx
39: 5d pop %ebp
3a: 8d 61 fc lea 0xfffffffc(%ecx),%esp
3d: c3 ret




Richard Henderson has done some work in both gcc and the assembler to emit
DWARF basic block markers. The compiler knows what the jump targets are in
code it generates. For inline assembly, the assembler supports emitting a



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