[Bug c++/55171] [4.7/4.8 Regression] incorrect virtual thunk on mingw

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55171

Kai Tietz <ktietz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-11-24
     Ever Confirmed|0                           |1

--- Comment #7 from Kai Tietz <ktietz at gcc dot gnu.org> 2012-11-24 12:47:37 UTC ---
Yes, the issue here is the generation of patterns - like

movl    (%ecx), %eax
addl    -12(%eax), %ecx

- for thunks.

The following patch solves this issue for me.

Index: i386.c
===================================================================
--- i386.c    (Revision 193669)
+++ i386.c    (Arbeitskopie)
@@ -9567,6 +9567,8 @@
       tree decl = current_function_decl, fntype = TREE_TYPE (decl);
       bool fastcall_p
     = lookup_attribute ("fastcall", TYPE_ATTRIBUTES (fntype)) != NULL_TREE;
+      bool thiscall_p
+    = lookup_attribute ("thiscall", TYPE_ATTRIBUTES (fntype)) != NULL_TREE;
       bool static_chain_p = DECL_STATIC_CHAIN (decl);
       int regparm = ix86_function_regparm (fntype, decl);
       int drap_regno
@@ -9577,10 +9579,13 @@
       if ((regparm < 1 || (fastcall_p && !static_chain_p))
       && drap_regno != AX_REG)
     regno = AX_REG;
-      else if (regparm < 2 && drap_regno != DX_REG)
+      else if (thiscall_p
+                 && !static_chain_p && drap_regno != DX_REG)
+          regno = DX_REG;
+      else if (regparm < 2 && !thiscall_p && drap_regno != DX_REG)
     regno = DX_REG;
       /* ecx is the static chain register.  */
-      else if (regparm < 3 && !fastcall_p && !static_chain_p
+      else if (regparm < 3 && !fastcall_p && !thiscall_p && !static_chain_p
            && drap_regno != CX_REG)
     regno = CX_REG;
       else if (ix86_save_reg (BX_REG, true))
@@ -11092,12 +11097,15 @@
     return R11_REG;
   else
     {
-      bool is_fastcall;
+      bool is_fastcall, is_thiscall;
       int regparm;

       is_fastcall = (lookup_attribute ("fastcall",
                        TYPE_ATTRIBUTES (TREE_TYPE (cfun->decl)))
              != NULL);
+      is_thiscall = (lookup_attribute ("thiscall",
+                       TYPE_ATTRIBUTES (TREE_TYPE (cfun->decl)))
+             != NULL);
       regparm = ix86_function_regparm (TREE_TYPE (cfun->decl), cfun->decl);

       if (is_fastcall)
@@ -11110,6 +11118,12 @@
         }
       return AX_REG;
     }
+      else if (is_thiscall)
+        {
+      if (!DECL_STATIC_CHAIN (cfun->decl))
+        return DX_REG;
+      return AX_REG;
+    }
       else if (regparm < 3)
     {
       if (!DECL_STATIC_CHAIN (cfun->decl))
@@ -25046,7 +25060,7 @@

       fntype = TREE_TYPE (fndecl);
       ccvt = ix86_get_callcvt (fntype);
-      if ((ccvt & (IX86_CALLCVT_FASTCALL | IX86_CALLCVT_THISCALL)) != 0)
+      if ((ccvt & IX86_CALLCVT_FASTCALL) != 0)
     {
       /* Fastcall functions use ecx/edx for arguments, which leaves
          us with EAX for the static chain.
@@ -25054,6 +25068,8 @@
          leaves us with EAX for the static chain.  */
       regno = AX_REG;
     }
+      else if ((ccvt & IX86_CALLCVT_THISCALL) != 0)
+        regno = DX_REG;
       else if (ix86_function_regparm (fntype, fndecl) == 3)
     {
       /* For regparm 3, we have no free call-clobbered registers in
@@ -34713,8 +34729,10 @@
   else
     {
       unsigned int ccvt = ix86_get_callcvt (TREE_TYPE (function));
-      if ((ccvt & (IX86_CALLCVT_FASTCALL | IX86_CALLCVT_THISCALL)) != 0)
+      if ((ccvt & IX86_CALLCVT_FASTCALL) != 0)
     tmp_regno = AX_REG;
+      else if ((ccvt & IX86_CALLCVT_THISCALL) != 0)
+        tmp_regno = DX_REG;
       else
     tmp_regno = CX_REG;
     }