re PR tree-optimization/87931 (ICE in vectorizable_reduction, at…

re PR tree-optimization/87931 (ICE in vectorizable_reduction, at tree-vect-loop.c:6193 since r265876)

2018-11-13  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87931
	* tree-vect-loop.c (vect_is_simple_reduction): Restrict
	nested cycles we support to latch computations vectorizable_reduction
	handles.

	* gcc.dg/graphite/pr87931.c: New testcase.

From-SVN: r266075

gcc/ChangeLog

+2018-11-13  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87931
+	* tree-vect-loop.c (vect_is_simple_reduction): Restrict
+	nested cycles we support to latch computations vectorizable_reduction
+	handles.
+
 2018-11-13  Martin Liska  <mliska@suse.cz>
 
 	PR tree-optimization/87885

gcc/testsuite/ChangeLog

+2018-11-13  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87931
+	* gcc.dg/graphite/pr87931.c: New testcase.
+
 2018-11-13  Martin Liska  <mliska@suse.cz>
 
 	PR sanitizer/87930

gcc/testsuite/gcc.dg/graphite/pr87931.c

+/* { dg-do compile } */
+/* { dg-options "-O3 -fno-tree-copy-prop -fgraphite-identity" } */
+
+#define N 40
+#define M 128
+float in[N+M];
+float coeff[M];
+float fir_out[N];
+
+void fir ()
+{
+  int i,j,k;
+  float diff;
+
+  for (i = 0; i < N; i++) {
+    diff = 0;
+    for (j = 0; j < M; j++) {
+      diff += in[j+i]*coeff[j];
+    }
+    fir_out[i] = diff;
+  }
+}

gcc/tree-vect-loop.c

@@ -2976,6 +2976,22 @@ vect_is_simple_reduction (loop_vec_info loop_info, stmt_vec_info phi_info,
 
   if (nested_in_vect_loop && !check_reduction)
     {
+      /* FIXME: Even for non-reductions code generation is funneled
+	 through vectorizable_reduction for the stmt defining the
+	 PHI latch value.  So we have to artificially restrict ourselves
+	 for the supported operations.  */
+      switch (get_gimple_rhs_class (code))
+	{
+	case GIMPLE_BINARY_RHS:
+	case GIMPLE_TERNARY_RHS:
+	  break;
+	default:
+	  /* Not supported by vectorizable_reduction.  */
+	  if (dump_enabled_p ())
+	    report_vect_op (MSG_MISSED_OPTIMIZATION, def_stmt,
+			    "nested cycle: not handled operation: ");
+	  return NULL;
+	}
       if (dump_enabled_p ())
 	report_vect_op (MSG_NOTE, def_stmt, "detected nested cycle: ");
       return def_stmt_info;