Re: [PATCH] [graphite] dump reasons why graphite failed to detect a scop

[Tobias Grosser]

On 07/25/2015 12:36 AM, Sebastian Pop wrote:

When trying to analyze why Graphite does not handle a loop nest, it is easy to
look in the dumps of -fdump-tree-graphite-all to guess what has to be changed to
catch the loop.  This patch makes the dumps a bit more verbose and useful.
---
  gcc/graphite-scop-detection.c | 72 +++++++++++++++++++++++++++++++++++++++----
  1 file changed, 66 insertions(+), 6 deletions(-)

LGTM.

Tobias

diff --git a/gcc/graphite-scop-detection.c b/gcc/graphite-scop-detection.c
index 686f495..fb7247e 100644
--- a/gcc/graphite-scop-detection.c
+++ b/gcc/graphite-scop-detection.c
@@ -51,6 +51,7 @@ along with GCC; see the file COPYING3.  If not see
  #include "graphite-poly.h"
  #include "tree-ssa-propagate.h"
  #include "graphite-scop-detection.h"
+#include "gimple-pretty-print.h"

  /* Forward declarations.  */
  static void make_close_phi_nodes_unique (basic_block);
@@ -350,13 +351,31 @@ stmt_simple_for_scop_p (basic_block scop_entry, loop_p 
outermost_loop,
        || (gimple_code (stmt) == GIMPLE_CALL
          && !(gimple_call_flags (stmt) & (ECF_CONST | ECF_PURE)))
        || (gimple_code (stmt) == GIMPLE_ASM))
-    return false;
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+       {
+         fprintf (dump_file, "[scop-detection-fail] ");
+         fprintf (dump_file, "Graphite cannot handle this stmt:\n");
+         print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS|TDF_MEMSYMS);
+       }
+
+      return false;
+    }

    if (is_gimple_debug (stmt))
      return true;

    if (!stmt_has_simple_data_refs_p (outermost_loop, stmt))
-    return false;
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+       {
+         fprintf (dump_file, "[scop-detection-fail] ");
+         fprintf (dump_file, "Graphite cannot handle data-refs in stmt:\n");
+         print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS|TDF_MEMSYMS);
+       }
+
+      return false;
+    }

    switch (gimple_code (stmt))
      {
@@ -375,7 +394,16 @@ stmt_simple_for_scop_p (basic_block scop_entry, loop_p 
outermost_loop,
              || code == GE_EXPR
              || code == EQ_EXPR
              || code == NE_EXPR))
-          return false;
+          {
+           if (dump_file && (dump_flags & TDF_DETAILS))
+             {
+               fprintf (dump_file, "[scop-detection-fail] ");
+               fprintf (dump_file, "Graphite cannot handle cond stmt:\n");
+               print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS|TDF_MEMSYMS);
+             }
+
+           return false;
+         }

        for (unsigned i = 0; i < 2; ++i)
          {
@@ -383,7 +411,16 @@ stmt_simple_for_scop_p (basic_block scop_entry, loop_p 
outermost_loop,
            if (!graphite_can_represent_expr (scop_entry, loop, op)
                /* We can not handle REAL_TYPE. Failed for pr39260.  */
                || TREE_CODE (TREE_TYPE (op)) == REAL_TYPE)
-             return false;
+             {
+               if (dump_file && (dump_flags & TDF_DETAILS))
+                 {
+                   fprintf (dump_file, "[scop-detection-fail] ");
+                   fprintf (dump_file, "Graphite cannot represent stmt:\n");
+                   print_gimple_stmt (dump_file, stmt, 0, 
TDF_VOPS|TDF_MEMSYMS);
+                 }
+
+               return false;
+             }
          }

        return true;
@@ -395,6 +432,12 @@ stmt_simple_for_scop_p (basic_block scop_entry, loop_p 
outermost_loop,

      default:
        /* These nodes cut a new scope.  */
+      if (dump_file && (dump_flags & TDF_DETAILS))
+       {
+         fprintf (dump_file, "[scop-detection-fail] ");
+         fprintf (dump_file, "Gimple stmt not handled in Graphite:\n");
+         print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS|TDF_MEMSYMS);
+       }
        return false;
      }

@@ -488,7 +531,16 @@ scopdet_basic_block_info (basic_block bb, loop_p 
outermost_loop,
         with make_forwarder_block.  */
        if (!single_succ_p (bb)
          || bb_has_abnormal_pred (single_succ (bb)))
-       result.difficult = true;
+       {
+         if (dump_file && (dump_flags & TDF_DETAILS))
+           {
+             fprintf (dump_file, "[scop-detection-fail] ");
+             fprintf (dump_file, "BB %d cannot be part of a scop.\n",
+                      bb->index);
+           }
+
+         result.difficult = true;
+       }
        else
        result.exit = single_succ (bb);

@@ -509,7 +561,15 @@ scopdet_basic_block_info (basic_block bb, loop_p 
outermost_loop,
        sinfo = build_scops_1 (bb, outermost_loop, &regions, loop);

        if (!graphite_can_represent_loop (entry_block, loop))
-         result.difficult = true;
+         {
+           if (dump_file && (dump_flags & TDF_DETAILS))
+             {
+               fprintf (dump_file, "[scop-detection-fail] ");
+               fprintf (dump_file, "Graphite cannot represent loop %d.\n",
+                        loop->num);
+             }
+           result.difficult = true;
+         }

        result.difficult |= sinfo.difficult;