[google] Emit relative addresses to function patch sections instead of absolute addresses. (issue6572065)

[Xinliang David Li]

xray feature is not in trunk yet.

David

On Fri, Oct 5, 2012 at 3:53 PM, Diego Novillo <dnovillo@google.com> wrote:
> Harshit, why didn't you propose this patch for trunk?  Why should we
> make it a google-local patch?
>
>
> Diego.
>
> On Fri, Sep 28, 2012 at 5:24 AM, Harshit Chopra <harshit@google.com> wrote:
>> commit fc3a55ccec9bc770c79f8a221f5abd397befc8f6
>> Author: Harshit Chopra <harshit@google.com>
>> Date:   Thu Sep 20 17:49:59 2012 -0700
>>
>>     Instead of emitting absolute addresses to the function patch sections, emit relative addresses. Absolute addresses might require relocation, which is time consuming and fraught with other issues.
>>
>> M       gcc/config/i386/i386.c
>>
>> Tested:
>>   Ran make check-gcc and manually confirmed that the affected tests pass.
>>
>> ChangeLog:
>>
>> 2012-09-28  Harshit Chopra  <harshit@google.com>
>>
>>         * gcc/config/i386/i386.c (ix86_output_function_nops_prologue_epilogue): Emit relative address to function patch sections.
>>
>> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>> index f72b0b5..8c9334f 100644
>> --- a/gcc/config/i386/i386.c
>> +++ b/gcc/config/i386/i386.c
>> @@ -11098,7 +11098,7 @@ ix86_output_function_nops_prologue_epilogue (FILE *file,
>>         $LFPEL0:
>>           <pre_instruction>
>>           0x90 (repeated num_actual_nops times)
>> -         .quad $LFPESL0
>> +         .quad $LFPESL0 - .
>>       followed by section 'section_name' which contains the address
>>       of instruction at 'label'.
>>     */
>> @@ -11110,7 +11110,10 @@ ix86_output_function_nops_prologue_epilogue (FILE *file,
>>      asm_fprintf (file, ASM_BYTE"0x90\n");
>>
>>    fprintf (file, ASM_QUAD);
>> +  /* Output "section_label - ." for the relative address of the entry in
>> +     the section 'section_name'.  */
>>    assemble_name_raw (file, section_label);
>> +  fprintf (file, " - .");
>>    fprintf (file, "\n");
>>
>>    /* Emit the backpointer section. For functions belonging to comdat group,
>> @@ -11144,7 +11147,7 @@ ix86_output_function_nops_prologue_epilogue (FILE *file,
>>           .quad $LFPEL0
>>     */
>>    ASM_OUTPUT_INTERNAL_LABEL (file, section_label);
>> -  fprintf(file, ASM_QUAD"\t");
>> +  fprintf(file, ASM_QUAD);
>>    assemble_name_raw (file, label);
>>    fprintf (file, "\n");
>>
>>
>> --
>> This patch is available for review at http://codereview.appspot.com/6572065