re PR tree-optimization/83323 (186.crafty miscompares)

Fix PR83323

	* gimple-loop-jam (unroll_jam_possible_p): Correct test for
	head-controlled loops and loop BBs.
	* common.opt (funroll-and-jam): Remove, instead ...
	(floop-unroll-and-jam): ... reuse this option.
	* opts.c (default_options_table): Use OPT_floop_unroll_and_jam.
	* doc/invoke.texi (-funroll-and-jam): Move docu to ...
	(-floop-unroll-and-jam): ... this option.

testsuite/
	* gcc.dg/pr83323.c: New test.
	* gcc.dg/unroll-and-jam.c: Use -floop-unroll-and-jam.

From-SVN: r255514

gcc/ChangeLog

+2017-12-08  Michael Matz  <matz@suse.de>
+
+	Fix PR tree-optimization/83323
+	* gimple-loop-jam (unroll_jam_possible_p): Correct test for
+	head-controlled loops and loop BBs.
+	* common.opt (funroll-and-jam): Remove, instead ...
+	(floop-unroll-and-jam): ... reuse this option.
+	* opts.c (default_options_table): Use OPT_floop_unroll_and_jam.
+	* doc/invoke.texi (-funroll-and-jam): Move docu to ...
+	(-floop-unroll-and-jam): ... this option.
+
 2017-12-08  Jakub Jelinek  <jakub@redhat.com>
 
 	* ipa-polymorphic-call.c (noncall_stmt_may_be_vtbl_ptr_store): Fix

gcc/common.opt

@@ -1512,8 +1512,8 @@ Common Alias(floop-nest-optimize)
 Enable loop nest transforms.  Same as -floop-nest-optimize.
 
 floop-unroll-and-jam
-Common Alias(floop-nest-optimize)
-Enable loop nest transforms.  Same as -floop-nest-optimize.
+Common Report Var(flag_unroll_jam) Optimization
+Perform unroll-and-jam on loops.
 
 fgnu-tm
 Common Report Var(flag_tm)
@@ -2695,10 +2695,6 @@ fsplit-loops
 Common Report Var(flag_split_loops) Optimization
 Perform loop splitting.
 
-funroll-and-jam
-Common Report Var(flag_unroll_jam) Optimization
-Perform unroll-and-jam on loops.
-
 funwind-tables
 Common Report Var(flag_unwind_tables) Optimization
 Just generate unwind tables for exception handling.

gcc/doc/invoke.texi

@@ -437,7 +437,7 @@ Objective-C and Objective-C++ Dialects}.
 -ftree-reassoc  -ftree-sink  -ftree-slsr  -ftree-sra @gol
 -ftree-switch-conversion  -ftree-tail-merge @gol
 -ftree-ter  -ftree-vectorize  -ftree-vrp  -funconstrained-commons @gol
--funit-at-a-time  -funroll-all-loops  -funroll-loops -funroll-and-jam @gol
+-funit-at-a-time  -funroll-all-loops  -funroll-loops @gol
 -funsafe-math-optimizations  -funswitch-loops @gol
 -fipa-ra  -fvariable-expansion-in-unroller  -fvect-cost-model  -fvpt @gol
 -fweb  -fwhole-program  -fwpa  -fuse-linker-plugin @gol
@@ -8511,11 +8511,9 @@ at @option{-O} and higher.
 @item -ftree-loop-linear
 @itemx -floop-strip-mine
 @itemx -floop-block
-@itemx -floop-unroll-and-jam
 @opindex ftree-loop-linear
 @opindex floop-strip-mine
 @opindex floop-block
-@opindex floop-unroll-and-jam
 Perform loop nest optimizations.  Same as
 @option{-floop-nest-optimize}.  To use this code transformation, GCC has
 to be configured with @option{--with-isl} to enable the Graphite loop
@@ -9789,8 +9787,8 @@ for one side of the iteration space and false for the other.
 Move branches with loop invariant conditions out of the loop, with duplicates
 of the loop on both branches (modified according to result of the condition).
 
-@item -funroll-and-jam
-@opindex funroll-and-jam
+@item -floop-unroll-and-jam
+@opindex floop-unroll-and-jam
 Apply unroll and jam transoformations on feasible loops.  In a loop
 nest this unrolls the outer loop by some factor and fuses the resulting
 multiple inner loops.

gcc/gimple-loop-jam.c

@@ -152,7 +152,7 @@ merge_loop_tree (struct loop *loop, struct loop *old)
   free (bbs);
 }
 
-/* BB exits the outer loop of an unroll-and-jam situation.
+/* BB is part of the outer loop of an unroll-and-jam situation.
    Check if any statements therein would prevent the transformation.  */
 
 static bool
@@ -160,9 +160,10 @@ bb_prevents_fusion_p (basic_block bb)
 {
   gimple_stmt_iterator gsi;
   /* BB is duplicated by outer unrolling and then all N-1 first copies
-     move into the body of the fused inner loop.  The last copy remains
-     the exit block of the outer loop and is still outside the inner loop
-     also after fusion.  We can't allow this for some effects of BB:
+     move into the body of the fused inner loop.  If BB exits the outer loop
+     the last copy still doess so, and the first N-1 copies are cancelled
+     by loop unrolling, so also after fusion it's the exit block.
+     But there might be other reasons that prevent fusion:
        * stores or unknown side-effects prevent fusion
        * loads don't
        * computations into SSA names: these aren't problematic.  Their
@@ -204,6 +205,19 @@ unroll_jam_possible_p (struct loop *outer, struct loop *loop)
   if (outer->inner != loop || loop->next)
     return false;
 
+  /* Prevent head-controlled inner loops, that we usually have.
+     The guard block would need to be accepted
+     (invariant condition either entering or skipping the loop),
+     without also accepting arbitrary control flow.  When unswitching
+     ran before us (as with -O3) this won't be a problem because its
+     outer loop unswitching will have moved out the invariant condition.
+
+     If we do that we need to extend fuse_loops() to cope with this
+     by threading through the (still invariant) copied condition
+     between the two loop copies.  */
+  if (!dominated_by_p (CDI_DOMINATORS, outer->latch, loop->header))
+    return false;
+
   /* The number of iterations of the inner loop must be loop invariant
      with respect to the outer loop.  */
   if (!number_of_iterations_exit (loop, single_exit (loop), &niter,
@@ -218,23 +232,8 @@ unroll_jam_possible_p (struct loop *outer, struct loop *loop)
   n = get_loop_body_with_size (outer, bbs, n_basic_blocks_for_fn (cfun));
 
   for (i = 0; i < n; i++)
-    {
-      if (bbs[i]->loop_father == outer
-	  && bbs[i] != outer->latch && bbs[i] != outer->header
-	  && (!loop_exits_from_bb_p (outer, bbs[i])
-	      || bb_prevents_fusion_p (bbs[i])))
-	break;
-      /* XXX Note that the above disallows head-controlled inner loops,
-         that we usually have.  The guard block would need to be accepted
-	 (invariant condition either entering or skipping the loop),
-	 without also accepting arbitrary control flow.  When unswitching
-	 ran before us (as with -O3) this won't be a problem because its
-	 outer loop unswitching will have moved out the invariant condition.
-	 
-	 If we do that we need to extend fuse_loops() to cope with this
-	 by threading through the (still invariant) copied condition
-	 between the two loop copies.  */
-    }
+    if (bbs[i]->loop_father == outer && bb_prevents_fusion_p (bbs[i]))
+      break;
   free (bbs);
   if (i != n)
     return false;

gcc/opts.c

@@ -536,7 +536,7 @@ static const struct default_options default_options_table[] =
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_finline_functions_called_once, NULL, 1 },
     { OPT_LEVELS_3_PLUS, OPT_fsplit_loops, NULL, 1 },
     { OPT_LEVELS_3_PLUS, OPT_funswitch_loops, NULL, 1 },
-    { OPT_LEVELS_3_PLUS, OPT_funroll_and_jam, NULL, 1 },
+    { OPT_LEVELS_3_PLUS, OPT_floop_unroll_and_jam, NULL, 1 },
     { OPT_LEVELS_3_PLUS, OPT_fgcse_after_reload, NULL, 1 },
     { OPT_LEVELS_3_PLUS, OPT_ftree_loop_vectorize, NULL, 1 },
     { OPT_LEVELS_3_PLUS, OPT_ftree_slp_vectorize, NULL, 1 },

gcc/testsuite/ChangeLog

+2017-12-08  Michael Matz  <matz@suse.de>
+
+	Fix PR tree-optimization/83323
+	* gcc.dg/pr83323.c: New test.
+	* gcc.dg/unroll-and-jam.c: Use -floop-unroll-and-jam.
+
 2017-12-08  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/81782

gcc/testsuite/gcc.dg/pr83323.c

+/* { dg-do run } */
+/* { dg-options "-O3 -floop-unroll-and-jam --param unroll-jam-min-percent=0" } */
+int x[1024], y[1024];
+
+void __attribute__((noipa)) foo ()
+{
+  for (int i = 0; i < 1024; ++i)
+    {
+      x[i] = 0;
+      for (int j = 0; j < 1024; ++j)
+        if (!y[j])
+          x[i] = 1;
+    }
+}
+
+int main()
+{
+  y[1023] = 1;
+  foo ();
+  if (x[1] != 1)
+    __builtin_abort ();
+  return 0;
+}

gcc/testsuite/gcc.dg/unroll-and-jam.c

 /* { dg-do run } */
-/* { dg-options "-O3 -funroll-and-jam --param unroll-jam-min-percent=0 -fdump-tree-unrolljam-details" } */
+/* { dg-options "-O3 -floop-unroll-and-jam --param unroll-jam-min-percent=0 -fdump-tree-unrolljam-details" } */
 /* { dg-require-effective-target int32plus } */
 
 #include <stdio.h>