[Bug c/88000] Different local vars regs order may produce different and so wrong code

["msebor at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88000

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |msebor at gcc dot gnu.org

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
GCC could help by issuing a warning for unsupported uses, like in the prototype
patch below:

Index: gcc/c/c-typeck.c
===================================================================
--- gcc/c/c-typeck.c    (revision 266033)
+++ gcc/c/c-typeck.c    (working copy)
@@ -6505,6 +6505,14 @@ convert_for_assignment (location_t location, locat
       objc_ok = objc_compare_types (type, rhstype, parmno, rname);
     }

+  if (VAR_P (rhs) && DECL_HARD_REGISTER (rhs)
+      && warning_at (expr_loc, OPT_Wasm_register_var,
+                    "unsupported use of a hard register %qD as "
+                    "argument %d of %qE",
+                    rhs, parmnum, rname))
+    inform (DECL_SOURCE_LOCATION (rhs),
+           "%qD declared here", rhs);
+
   if (warn_cxx_compat)
     {
       tree checktype = origtype != NULL_TREE ? origtype : rhstype;
Index: gcc/c-family/c.opt
===================================================================
--- gcc/c-family/c.opt  (revision 266033)
+++ gcc/c-family/c.opt  (working copy)
@@ -338,6 +338,10 @@ Warray-bounds=
 LangEnabledBy(C ObjC C++ LTO ObjC++,Wall,1,0)
 ; in common.opt

+Wasm-register-var
+ObjC ObjC++ Var(warn_asm_register_var) Warning LangEnabledBy(C ObjC C++
ObjC++, Wall)
+Warn for unsupported uses of variables declared asm register.
+
 Wassign-intercept
 ObjC ObjC++ Var(warn_assign_intercept) Warning
 Warn whenever an Objective-C assignment is being intercepted by the garbage
collector.