Keep track of the FUNCTION_BEG note

function.cc emits a NOTE_FUNCTION_BEG after all arguments have
been copied to pseudos.  It then records this note in parm_birth_insn.
Various other pieces of code use this insn as a convenient place to
insert things at the start of the function.

However, cfgexpand later changes parm_birth_insn as follows:

  /* If we emitted any instructions for setting up the variables,
     emit them before the FUNCTION_START note.  */
  if (var_seq)
    {
      emit_insn_before (var_seq, parm_birth_insn);

      /* In expand_function_end we'll insert the alloca save/restore
	 before parm_birth_insn.  We've just insertted an alloca call.
	 Adjust the pointer to match.  */
      parm_birth_insn = var_seq;
    }

But the FUNCTION_BEG note is still useful for things that aren't
sensitive to stack allocation, and it has the advantage that
(unlike the var_seq above) it is never deleted or combined.
This patch adds a separate variable to track it.

gcc/
	* emit-rtl.h (rtl_data::x_function_beg_note): New member variable.
	(function_beg_insn): New macro.
	* function.cc (expand_function_start): Initialize function_beg_insn.

1 files changed, 1 insertions, 1 deletions

diff --git a/gcc/function.cc b/gcc/function.cc
index de356f7..5ffd438 100644
--- a/gcc/function.cc
+++ b/gcc/function.cc
@@ -5202,7 +5202,7 @@ expand_function_start (tree subr)
 
   gcc_assert (NOTE_P (get_last_insn ()));
 
-  parm_birth_insn = get_last_insn ();
+  function_beg_insn = parm_birth_insn = get_last_insn ();
 
   /* If the function receives a non-local goto, then store the
      bits we need to restore the frame pointer.  */