re PR middle-end/91195 (incorrect may be used uninitialized smw (272711, 273474])

	PR middle-end/91195
	* tree-ssa-phiopt.c (cond_store_replacement): Move lhs unsharing
	earlier.  Set TREE_NO_WARNING on the rhs1 of the artificially added
	load.

	* gcc.dg/pr91195.c: New test.

From-SVN: r278479

gcc/ChangeLog

+2019-11-20  Jiangning Liu  <jiangning.liu@amperecomputing.com>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/91195
+	* tree-ssa-phiopt.c (cond_store_replacement): Move lhs unsharing
+	earlier.  Set TREE_NO_WARNING on the rhs1 of the artificially added
+	load.
+
 2019-11-20  Georg-Johann Lay  <avr@gjlay.de>
 
 	Make 0-series device specs work with older versions of avr-gcc.

gcc/testsuite/ChangeLog

+2019-11-20  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/91195
+	* gcc.dg/pr91195.c: New test.
+
 2019-11-20  Richard Biener  <rguenther@suse.de>
 
 	PR c/92088

gcc/testsuite/gcc.dg/pr91195.c

+/* PR middle-end/91195 */
+/* { dg-do compile } */
+/* { dg-options "-Wmaybe-uninitialized -O2" } */
+
+int bar (char*);
+
+void
+foo (char *x, char *y)
+{
+  char *a[2];
+  int b = 0;
+
+  if (x)
+    a[b++] = x;		/* { dg-bogus "may be used uninitialized in this function" } */
+  if (y)
+    a[b++] = y;
+
+  for (int j = 0; j < 4; j++) 
+    switch (j)
+      {
+      case 0:
+	if (b == 0 || bar (a[0]))
+	  break;
+      }
+}

gcc/tree-ssa-phiopt.c

@@ -2269,6 +2269,10 @@ cond_store_replacement (basic_block middle_bb, basic_block join_bb,
   name = make_temp_ssa_name (TREE_TYPE (lhs), NULL, "cstore");
   new_stmt = gimple_build_assign (name, lhs);
   gimple_set_location (new_stmt, locus);
+  lhs = unshare_expr (lhs);
+  /* Set TREE_NO_WARNING on the rhs of the load to avoid uninit
+     warnings.  */
+  TREE_NO_WARNING (gimple_assign_rhs1 (new_stmt)) = 1;
   gsi_insert_on_edge (e1, new_stmt);
 
   /* 3) Create a PHI node at the join block, with one argument
@@ -2279,7 +2283,6 @@ cond_store_replacement (basic_block middle_bb, basic_block join_bb,
   add_phi_arg (newphi, rhs, e0, locus);
   add_phi_arg (newphi, name, e1, locus);
 
-  lhs = unshare_expr (lhs);
   new_stmt = gimple_build_assign (lhs, PHI_RESULT (newphi));
 
   /* 4) Insert that PHI node.  */