[rtlanal] Fix rtl-optimization/71295

PR rtl-optimization/71295
	* rtlanal.c (subreg_get_info): If taking a subreg at the requested
	offset would go over the size of the inner mode reject it.

	* gcc.c-torture/compile/pr71295.c: New test.

From-SVN: r237034

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2016-06-02  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR rtl-optimization/71295
+	* rtlanal.c (subreg_get_info): If taking a subreg at the requested
+	offset would go over the size of the inner mode reject it.
+
 2016-06-02  Jakub Jelinek  <jakub@redhat.com>
 
 	* config/i386/sse.md (*vec_concatv4si): Use v=v,v instead of

gcc/rtlanal.c

@@ -3657,6 +3657,16 @@ subreg_get_info (unsigned int xregno, machine_mode xmode,
 	  info->offset = offset / regsize_xmode;
 	  return;
 	}
+      /* It's not valid to extract a subreg of mode YMODE at OFFSET that
+	 would go outside of XMODE.  */
+      if (!rknown
+	  && GET_MODE_SIZE (ymode) + offset > GET_MODE_SIZE (xmode))
+	{
+	  info->representable_p = false;
+	  info->nregs = nregs_ymode;
+	  info->offset = offset / regsize_xmode;
+	  return;
+	}
       /* Quick exit for the simple and common case of extracting whole
 	 subregisters from a multiregister value.  */
       /* ??? It would be better to integrate this into the code below,

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2016-06-02  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR rtl-optimization/71295
+	* gcc.c-torture/compile/pr71295.c: New test.
+
 2016-06-02  Jakub Jelinek  <jakub@redhat.com>
 
 	* gcc.target/i386/avx512vl-concatv4si-1.c: New test.

gcc/testsuite/gcc.c-torture/compile/pr71295.c

@@ -0,0 +1,12 @@
+extern void fn2 (long long);
+int a;
+
+void
+fn1 ()
+{
+  long long b[3];
+  a = 0;
+  for (; a < 3; a++)
+    b[a] = 1;
+  fn2 (b[1]);
+}