[trans-mem] PR47690: redirect recursive calls in a clone correctly

[Aldy Hernandez <aldyh at redhat dot com>]

Consider a sample where a transaction callable function has a recursive 
call to itself:

int george;
void NewQueueNode()
{
        __transaction [[atomic]] { george=999; }
        NewQueueNode();
}

Currently, when we are transforming calls to their transactional clone 
counterparts, we stop transforming once we reach the end of a 
transaction.  Ultimately, this means that in the cloned function, the 
recursive call to NewQueueNode() will have the edges redirected to the 
clone, but the gimple_call_fndecl() in the clone will still be pointing 
to the original function.  This causes cgraph verification to fail with 
a "edge points to wrong declaration" ICE.

I think the original (not-cloned) version of NewQueueNode() should 
recurse to the original version.  And the cloned version of 
NewQueueNode() should recurse to the cloned function.  I have done this 
in the patch below by continuing the call transformation past the end of 
a transaction, but only on recursive calls to the cloned function.

With my patch, the original function gets instrumented like this:

NewQueueNode:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $8, %esp
        movl    $41, %eax
        call    _ITM_beginTransaction
        movl    $999, %edx
        movl    $george, %eax
        call    _ITM_WU4
        call    _ITM_commitTransaction
        call    NewQueueNode
        leave

And the cloned function gets instrumented like this:

_ZGTt12NewQueueNode:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $8, %esp
        movl    $41, %eax
        call    _ITM_beginTransaction
        movl    $999, %edx
        movl    $george, %eax
        call    _ITM_WU4
        call    _ITM_commitTransaction
        call    _ZGTt12NewQueueNode
        leave

What do you think?
Aldy

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