[gcc r12-3342] Improve backwards threader debugging dumps.

[gcc r12-3342] Improve backwards threader debugging dumps.

[Aldy Hernandez]

https://gcc.gnu.org/g:779275c0835b58325f806568836c8b5081d1f52f

commit r12-3342-g779275c0835b58325f806568836c8b5081d1f52f
Author: Aldy Hernandez <aldyh@redhat.com>
Date:   Fri Sep 3 10:57:33 2021 +0200

    Improve backwards threader debugging dumps.
    
    This patch adds debugging helpers to the backwards threader.  I have
    also noticed that profitable_path_p() can bail early on paths that
    crosses loops and leave the dump of blocks incomplete.  Fixed as
    well.
    
    Unfortunately the new methods cannot be marked const, because we call
    the solver's dump which is not const.  I believe this was because the
    ranger dump calls m_cache.block_range().  This could probably use a
    cleanup at a later time.
    
    Tested on x86-64 Linux.
    
    gcc/ChangeLog:
    
            * tree-ssa-threadbackward.c (back_threader::dump): New.
            (back_threader::debug): New.
            (back_threader_profitability::profitable_path_p): Dump blocks
            even if we are bailing early.

Diff:
---
 gcc/tree-ssa-threadbackward.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
index 3aad1493c4d..b9a0d9a60ad 100644
--- a/gcc/tree-ssa-threadbackward.c
+++ b/gcc/tree-ssa-threadbackward.c
@@ -42,6 +42,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimple-range-path.h"
 #include "ssa.h"
 #include "tree-cfgcleanup.h"
+#include "tree-pretty-print.h"
 
 // Path registry for the backwards threader.  After all paths have been
 // registered with register_path(), thread_through_all_blocks() is called
@@ -89,6 +90,8 @@ private:
   edge find_taken_edge (const vec<basic_block> &path);
   edge find_taken_edge_cond (const vec<basic_block> &path, gcond *);
   edge find_taken_edge_switch (const vec<basic_block> &path, gswitch *);
+  virtual void debug ();
+  virtual void dump (FILE *out);
 
   back_threader_registry m_registry;
   back_threader_profitability m_profit;
@@ -519,6 +522,30 @@ debug (const vec <basic_block> &path)
   dump_path (stderr, path);
 }
 
+void
+back_threader::dump (FILE *out)
+{
+  m_solver.dump (out);
+  fprintf (out, "\nCandidates for pre-computation:\n");
+  fprintf (out, "===================================\n");
+
+  bitmap_iterator bi;
+  unsigned i;
+
+  EXECUTE_IF_SET_IN_BITMAP (m_imports, 0, i, bi)
+    {
+      tree name = ssa_name (i);
+      print_generic_expr (out, name, TDF_NONE);
+      fprintf (out, "\n");
+    }
+}
+
+void
+back_threader::debug ()
+{
+  dump (stderr);
+}
+
 back_threader_registry::back_threader_registry (int max_allowable_paths)
   : m_max_allowable_paths (max_allowable_paths)
 {
@@ -607,6 +634,14 @@ back_threader_profitability::profitable_path_p (const vec<basic_block> &m_path,
 	  if (bb->loop_father != loop)
 	    {
 	      path_crosses_loops = true;
+
+	      // Dump rest of blocks.
+	      if (dump_file && (dump_flags & TDF_DETAILS))
+		for (j++; j < m_path.length (); j++)
+		  {
+		    bb = m_path[j];
+		    fprintf (dump_file, " bb:%i", bb->index);
+		  }
 	      break;
 	    }