stack-clash: Add LR assert to layout_frame.

Since stack clash depends on the LR being saved for non-leaf functions this
patch adds an assert such that if this changes we would notice this.

gcc/
	PR target/86486
	* config/aarch64/aarch64.c (aarch64_layout_frame): Add assert.

From-SVN: r264748

gcc/ChangeLog

+2018-10-01  Tamar Christina  <tamar.christina@arm.com>
+
+	PR target/86486
+	* config/aarch64/aarch64.c (aarch64_layout_frame): Add assert.
+
 2018-10-01  Jeff Law  <law@redhat.com>
 	    Richard Sandiford <richard.sandiford@linaro.org>
 	    Tamar Christina  <tamar.christina@arm.com>

gcc/config/aarch64/aarch64.c

@@ -4094,6 +4094,11 @@ aarch64_layout_frame (void)
       offset = 2 * UNITS_PER_WORD;
     }
 
+  /* With stack-clash, LR must be saved in non-leaf functions.  */
+  gcc_assert (crtl->is_leaf
+	      || (cfun->machine->frame.reg_offset[R30_REGNUM]
+		  != SLOT_NOT_REQUIRED));
+
   /* Now assign stack slots for them.  */
   for (regno = R0_REGNUM; regno <= R30_REGNUM; regno++)
     if (cfun->machine->frame.reg_offset[regno] == SLOT_REQUIRED)