Re: Possible improvement to i386 function prologue analysis.

[Mark Kettenis <kettenis at gnu dot org>]

   Date: Fri, 15 Oct 2004 18:18:50 +0530
   From: ashish mittal <ashishm@linsyssoft.com>

   Hi,

   0807a380 <captured_main>:
    807a380:       55                      push   %ebp
    807a381:       31 c0                   xor    %eax,%eax
    807a383:       89 e5                   mov    %esp,%ebp
    807a385:       57                      push   %edi
    807a386:       31 d2                   xor    %edx,%edx
    807a388:       31 c9                   xor    %ecx,%ecx
    807a38a:       56                      push   %esi
    807a38b:       53                      push   %ebx
    807a38c:       81 ec 4c 01 00 00       sub    $0x14c,%esp

   In the above instance, the function "i386_analyze_register_saves()", 
   which takes care of populating the frame cache, will fail after reading 
   the first register %edi.

Hi Ashish,

Thanks for your mail.  I agree with you analysis.  There's even a
KFAILing test in the testsuite for a very similar problem.

   Please suggest if it would be worthwhile to work on a similar check for 
   special instructions within the for loop in i386_analyze_register_saves().
   This will enable it to continue reading saved registers over such 
   occurances.

It's not as important as getting the stack frame setup right (which is
why the code in i386_analyze_frame_setup is there), but it would
certainly be nice to have it.  There a slight complication though.
The prologue analyzing stuff is also used for implementing
i386_skip_prologue().  Now i386_skip_prologue() shouldn't dwell too
far into the function.  Skipping the instructions we're talking about
here might just do that.

   I could work on a possible patch if you agree.

That'd be great.

Mark