llvm dev - Mar 2017 - get function parameters (not arguments)

I tried the original posted code again:

for (auto& A : cast<CallInst>(BI)->arg_operands())
errs() << "--- " << A->getName() <<
"\n";

but it prints empty (only ---)!

Thank you and best,
Mo



On Fri, Mar 10, 2017 at 4:44 PM, Tim Northover <t.p.northover at
gmail.com>
wrote:
> On 10 March 2017 at 15:41, Mohammad Norouzi <mnmomn at gmail.com>
wrote:
> > Sorry i'm using the following code:
> >
> > F = (cast<CallInst>(BI))->getCalledFunction();
> > for (auto& A : F->getArgumentList()) {
> >                     errs() << "------- " <<
A.getName() << " " << "11" <<
> > "\n";
> >            }
> >
> > But how can I get the parameters (as e and f in the example)?
>
> The code you originally posted (using
> cast<CallInst>(BI)->arg_operands()) should iterate through the
> arguments to the call.
>
> Cheers.
>
> Tim.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20170310/3dd4861b/attachment.html>

On 10 March 2017 at 15:49, Mohammad Norouzi <mnmomn at gmail.com>
wrote:
> for (auto& A : cast<CallInst>(BI)->arg_operands())
> errs() << "--- " << A->getName() <<
"\n";
Ah, I see. You actually want "e" as a name. Unforuntately this
isn't
possible in general for a few reasons.

First, release builds of LLVM drop most Value names for efficiency
reasons. Without optimization your IR would just have numbers in the
arg position: "call void @foo(i32 %3, i32 %4)". Even those numbers
don't exist in memory, but are constructed as needed.

Another confounding factor is that optimization will turn even that
into a plain "call void @foo(i32 10, i32 22)" with no record of what
the original arguments were.

It gets even worse at the C level. If you saw "foo(a + b)", that
argument doesn't really have a natural name. It's a temporary
expression.

So in general you shouldn't be relying on the name for any actual
transformation you do.

For debugging there are usually alternatives that might not be quite
so convenient but do the job: Just dumping the argument is usually
sufficient; with heroic effort you might be able to use any debug info
that's present.

Cheers.

Tim.

what about the memory address of e and f? can i get them?

Thank you and best,
Mo

On Fri, Mar 10, 2017 at 5:02 PM, Tim Northover <t.p.northover at
gmail.com>
wrote:
> On 10 March 2017 at 15:49, Mohammad Norouzi <mnmomn at gmail.com>
wrote:
> > for (auto& A : cast<CallInst>(BI)->arg_operands())
> > errs() << "--- " << A->getName() <<
"\n";
>
> Ah, I see. You actually want "e" as a name. Unforuntately this
isn't
> possible in general for a few reasons.
>
> First, release builds of LLVM drop most Value names for efficiency
> reasons. Without optimization your IR would just have numbers in the
> arg position: "call void @foo(i32 %3, i32 %4)". Even those
numbers
> don't exist in memory, but are constructed as needed.
>
> Another confounding factor is that optimization will turn even that
> into a plain "call void @foo(i32 10, i32 22)" with no record of
what
> the original arguments were.
>
> It gets even worse at the C level. If you saw "foo(a + b)", that
> argument doesn't really have a natural name. It's a temporary
> expression.
>
> So in general you shouldn't be relying on the name for any actual
> transformation you do.
>
> For debugging there are usually alternatives that might not be quite
> so convenient but do the job: Just dumping the argument is usually
> sufficient; with heroic effort you might be able to use any debug info
> that's present.
>
> Cheers.
>
> Tim.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20170310/d6cb6973/attachment.html>