Question on -fopt-info-inline

[Qing Zhao]

> On Jul 3, 2018, at 7:19 PM, Jeff Law <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; 
>>>>> }
>>>>> 
>>>>> [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
>>>>> 	.globl	compute
>>>>> 	.type	compute, @function
>>>>> compute:
>>>>> .LFB3:
>>>>> 	.cfi_startproc
>>>>> 	movl	v_a(%rip), %edx
>>>>> 	movl	v_b(%rip), %eax
>>>>> 	leal	-10(%rdx,%rax), %eax
>>>>> 	movl	%eax, result(%rip)
>>>>> 	ret
>>>>> 	.cfi_endproc
>>>>> .LFE3:
>>>>> 	.size	compute, .-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=86395 <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86395> 
>> 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?

>  In fact, inlining and
> vectorization are the two use cases we identified internally as the
> first targets.

actually, during my study, I noticed that vectorization, some loop transformation, and OMP
are all generating information for -fopt-info (might not be complete yet, though). But inliner
is generating Nothing for -fopt-info.

Qing
> 
> 
> jeff