call_insns in RTX form--two questions

[Mike Stump]

[ I wasn't going to answer this, because you've left out all the  
details that would be required for me to answer it well, but since  
you've asked me specifically to answer, I'll try.  ]

On May 29, 2006, at 9:09 PM, sean yang wrote:
> The first question is: If I want to find a BB that containing a  
> specific function call (say 'foo'), is there an easy way in the RTX  
> level?

Yes or no, depending on what you consider easy and how you define the  
problem.  Anyway, if you look at the rtl:

(call_insn 8 28 9 0 (parallel [
             (call (mem:SI (symbol_ref:SI ("&L_foo$stub")  
<function_decl 0x41687b00 foo>) [0 S4 A8])
                 (const_int 32 [0x20]))
             (use (const_int 0 [0x0]))
             (clobber (reg:SI 65 lr))
         ]) 368 {*call_nonlocal_sysv} (nil)
     (nil)
     (nil))

all you have to do it wonder the insns looking for a call_insn and  
then check to see if the form is (mem (symbol_ref X)), and then check  
to see if the X mentioned is the one your interested in.  The above  
is a nice example, because it shows that the spelling of X need not  
be very portable, so doing this reliably can be `hard'.

Further, the compiler can use a register and an indirect call, thus  
making strcmp for the function name non-trivial.  If you want to wave  
your hands and not solve that problem, it is then easier, if not,  
then it can be impossible to solve.  As impossible as:

main() {
	extern (*bar)():
	(*bar)();
}

is to figure out.  However, it need not be that hard, could only be  
as hard as checking the NOTEs structure and doing a strcmp on them.   
That is easy to do.

Hint, if pr can show you the information you're interested in, then,  
trivially, the answer is yes.  Just follow the rtl dumper to the info  
you want.

> The second one is: how can i get the order of different call foo in  
> the final assembly code.

The language gap causes this question to be hard for us to  
understand.  If you told us what you're trying to do and why in 20  
pages or more it would be easier to answer.

> Can I get it by dumping some information, say the order of the  
> instruction link list, in RTL representation?

First, you never defined what ordering you want.  Do you want order  
as defined by the address of the instruction?  Do you want source  
code order?  Do you want order in the rtl for the function?

For rtl order, yes, just walk the rtl in order, and the first call to  
foo is the first, and the second call to foo is the second...

For source code order, you can approximate it by checking the debug  
line information associated with call in question.  Just collect all  
that info, sort increasing by line, the first one is first, the  
second one is second and so on.  This, as you can tell can't help  
with multiple calls to foo on the same line nor with compiles that  
lack debug information.  Though, if one throws the column numbers  
into the debug information, then one can solve for multiple calls on  
one line as well.  EXPR_LOCATION and EXPR_LINENO might have some of  
the data you're interested in.

For address ordering, well, generally that is the same as rtl order,  
but hot/cold partitioning can alter that.  I'll not answer this, as  
I'm hoping you don't care about the details.