re PR tree-optimization/92704 (ICE: Segmentation fault (in process_bb))

2019-11-29  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/92704
	* tree-if-conv.c (combine_blocks): Deal with virtual PHIs
	in loops performing only loads.

	* gcc.dg/torture/pr92704.c: New testcase.

From-SVN: r278828

gcc/ChangeLog

+2019-11-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/92704
+	* tree-if-conv.c (combine_blocks): Deal with virtual PHIs
+	in loops performing only loads.
+
 2019-11-29  Julian Brown  <julian@codesourcery.com>
 
 	* builtin-types.def (BT_DFLOAT32_PTR, BT_DFLOAT64_PTR,

gcc/testsuite/ChangeLog

+2019-11-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/92704
+	* gcc.dg/torture/pr92704.c: New testcase.
+
 2019-11-29  Joseph Myers  <joseph@codesourcery.com>
 
 	* objc.dg/attributes/gnu2x-attr-syntax-1.m: New test.

gcc/testsuite/gcc.dg/torture/pr92704.c

+/* { dg-do compile } */
+/* { dg-additional-options "-fexceptions -fnon-call-exceptions -fno-tree-dce -ftree-loop-if-convert" } */
+int zr, yx;
+
+void __attribute__ ((simd))
+oj (int rd, int q7)
+{
+  int wo = (__UINTPTR_TYPE__)&rd;
+
+  while (q7 < 1)
+    {
+      int kv;
+      short int v3;
+
+      for (v3 = 0; v3 < 82; v3 += 3)
+        {
+        }
+
+      kv = zr ? 0 : v3;
+      yx = kv < rd;
+      zr = zr && yx;
+      ++q7;
+    }
+}

gcc/tree-if-conv.c

@@ -2624,6 +2624,11 @@ combine_blocks (class loop *loop)
       vphi = get_virtual_phi (bb);
       if (vphi)
 	{
+	  /* When there's just loads inside the loop a stray virtual
+	     PHI merging the uses can appear, update last_vdef from
+	     it.  */
+	  if (!last_vdef)
+	    last_vdef = gimple_phi_arg_def (vphi, 0);
 	  imm_use_iterator iter;
 	  use_operand_p use_p;
 	  gimple *use_stmt;
@@ -2655,6 +2660,10 @@ combine_blocks (class loop *loop)
 	      if (gimple_vdef (stmt))
 		last_vdef = gimple_vdef (stmt);
 	    }
+	  else
+	    /* If this is the first load we arrive at update last_vdef
+	       so we handle stray PHIs correctly.  */
+	    last_vdef = gimple_vuse (stmt);
 	  if (predicated[i])
 	    {
 	      ssa_op_iter i;