[PATCH] Perform frame_pointer_needed hfp -> cfa replacements even if fp setter is not in the first bb (PR debug/54402)

[Jakub Jelinek]

Hi!

The following patch should fix the var-tracking slowness on the
reflect/check testcases where one of the test routines was compiling for
almost 50 minutes.  The problem was that there is a huge routine that is
shrink wrapped (or perhaps just the split stack prologue is multi-bb),
and I was trying to be too conservative when adding frame_pointer_needed
hard_frame_pointer_rtx VTA replacements.  Without those replacements we
weren't using DW_OP_fbreg for the hard frame pointer based mem accesses (so
unnecessarily large debug info), but what's worse is that on the hfp VALUE
we got almost 1200 reverse ops in the locs chain, so find_base_term as well
as get_addr has been quite costly.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2012-10-29  Jakub Jelinek  <ja...@redhat.com>

        PR debug/54402
        * var-tracking.c (fp_setter): Return false if there is REG_CFA_RESTORE
        hfp note.
        (vt_initialize): Look for fp_setter in any bb, not just successor of
        entry bb.

--- gcc/var-tracking.c.jj       2012-10-29 12:16:23.000000000 +0100
+++ gcc/var-tracking.c  2012-10-29 17:58:06.629025339 +0100
@@ -9535,24 +9535,33 @@ vt_add_function_parameters (void)
 static bool
 fp_setter (rtx insn)
 {
-  rtx pat = PATTERN (insn);
+  rtx pat = PATTERN (insn), expr;
   if (RTX_FRAME_RELATED_P (insn))
     {
-      rtx expr = find_reg_note (insn, REG_FRAME_RELATED_EXPR, NULL_RTX);
+      expr = find_reg_note (insn, REG_FRAME_RELATED_EXPR, NULL_RTX);
       if (expr)
        pat = XEXP (expr, 0);
     }
   if (GET_CODE (pat) == SET)
-    return SET_DEST (pat) == hard_frame_pointer_rtx;
+    {
+      if (SET_DEST (pat) != hard_frame_pointer_rtx)
+       return false;
+    }
   else if (GET_CODE (pat) == PARALLEL)
     {
       int i;
       for (i = XVECLEN (pat, 0) - 1; i >= 0; i--)
        if (GET_CODE (XVECEXP (pat, 0, i)) == SET
            && SET_DEST (XVECEXP (pat, 0, i)) == hard_frame_pointer_rtx)
-         return true;
+         break;
+      if (i < 0)
+       return false;
     }
-  return false;
+  else
+    return false;
+  if (find_reg_note (insn, REG_CFA_RESTORE, hard_frame_pointer_rtx))
+    return false;
+  return true;
 }
 
 /* Initialize cfa_base_rtx, create a preserved VALUE for it and
@@ -9600,7 +9609,7 @@ vt_init_cfa_base (void)
 static bool
 vt_initialize (void)
 {
-  basic_block bb, prologue_bb = single_succ (ENTRY_BLOCK_PTR);
+  basic_block bb;
   HOST_WIDE_INT fp_cfa_offset = -1;
 
   alloc_aux_for_blocks (sizeof (struct variable_tracking_info_def));
@@ -9858,8 +9867,7 @@ vt_initialize (void)
                      VTI (bb)->out.stack_adjust += post;
                    }
 
-                 if (bb == prologue_bb
-                     && fp_cfa_offset != -1
+                 if (fp_cfa_offset != -1
                      && hard_frame_pointer_adjustment == -1
                      && RTX_FRAME_RELATED_P (insn)
                      && fp_setter (insn))

        Jakub