Question on -fopt-info-inline

[Jeff Law]

On 07/05/2018 09:27 AM, Qing Zhao wrote:
> 
>> On Jul 3, 2018, at 7:19 PM, Jeff Law <law@redhat.com
>> <mailto:law@redhat.com>> wrote:
>>
>> On 07/03/2018 12:28 PM, Qing Zhao wrote:
>>>
>>>>>
>>>>>>
>>>>>> In order to collect complete information on all the inlining
>>>>>> transformation that GCC applies on a given program,
>>>>>> I searched online, and found that the option -fopt-info-inline
>>>>>> might be
>>>>>> the right option to use:
>>>>>>
>>>>>> in which, it mentioned:
>>>>>>
>>>>>> "As another example,
>>>>>> gcc -O3 -fopt-info-inline-optimized-missed=inline.txt
>>>>>> outputs information about missed optimizations as well as optimized
>>>>>> locations from all the inlining passes into inline.txt. 
>>>>>>
>>>>>> “
>>>>>>
>>>>>> Then I checked a very small testcase with GCC9 as following:
>>>>>>
>>>>>> [qinzhao@localhost inline_report]$ cat inline_1.c
>>>>>> static int foo (int a)
>>>>>> {
>>>>>> return a + 10;
>>>>>> }
>>>>>>
>>>>>> static int bar (int b)
>>>>>> {
>>>>>> return b - 20;
>>>>>> }
>>>>>>
>>>>>> static int boo (int a, int b)
>>>>>> {
>>>>>> return foo (a) + bar (b);
>>>>>> }
>>>>>>
>>>>>> extern int v_a, v_b;
>>>>>> extern int result;
>>>>>>
>>>>>> int compute ()
>>>>>> {
>>>>>> result = boo (v_a, v_b);
>>>>>> return result;Â 
>>>>>> }
>>>>>>
>>>>>> [qinzhao@localhost inline_report]$
>>>>>> /home/qinzhao/Install/latest/bin/gcc
>>>>>> -O3 -fopt-info-inline-optimized-missed=inline.txt inline_1.c -S
>>>>>> [qinzhao@localhost inline_report]$ ls -l inline.txt
>>>>>> -rw-rw-r--. 1 qinzhao qinzhao 0 Jul  3 11:25 inline.txt
>>>>>> [qinzhao@localhost inline_report]$ cat inline_1.s
>>>>>> .file"inline_1.c"
>>>>>> .text
>>>>>> .p2align 4,,15
>>>>>> .globlcompute
>>>>>> .typecompute, @function
>>>>>> compute:
>>>>>> .LFB3:
>>>>>> .cfi_startproc
>>>>>> movlv_a(%rip), %edx
>>>>>> movlv_b(%rip), %eax
>>>>>> leal-10(%rdx,%rax), %eax
>>>>>> movl%eax, result(%rip)
>>>>>> ret
>>>>>> .cfi_endproc
>>>>>> .LFE3:
>>>>>> .sizecompute, .-compute
>>>>>> .ident"GCC: (GNU) 9.0.0 20180702 (experimental)"
>>>>>> .section.note.GNU-stack,"",@progbits
>>>>>>
>>>>>> From the above, we can see:
>>>>>> 1. the call chains to —>“boo”->”foo”, “bar” in the routine “compute”
>>>>>> are completely inlined into “compute”;
>>>>>> 2. However, there is NO any inline information is dumped into
>>>>>> “inline.txt”.
>>>>>>
>>>>>>
>>>>>> So, My questions are:
>>>>>>
>>>>>> 1. Is the option -fopt-info-inline  the right option to use to get the
>>>>>> complete inlining transformation info from GCC?
>>>>>> 2. is this a bug that the current -fopt-info-inline cannot dump
>>>>>> anything for this testing case?
>>>>>
>>>>> I think the early inliner doesn't use opt-info yet. 
>>>>
>>>> so, shall we add the opt-info support to early inliner?
>>>
>>> I just created the following PR to record this work:
>>>
>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86395Â 
>>> let me know if I missed anything.
>> I'm hoping that the work David is doing WRT optimization information
>> will be usable for the inliner as well. 
> 
> where can I find more details of David’s work?
I don't have pointers to all the discussion handy.  BUt here's one of
the early messages:

https://gcc.gnu.org/ml/gcc-patches/2018-05/msg01675.html
jeff