Re: [patch i386} Fix PR 55171 - [4.7/4.8 Regression] incorrect virtual thunk on mingw

[Kai Tietz <ktietz70@googlemail.com>]

Fine.  Here is a adjusted version which keeps old abi behavior for
chain-registers.

2012-11-28  Kai Tietz

        PR target/55171
        * i386.c (get_scratch_register_on_entry): Handle
        thiscall-convention.
        (split_stack_prologue_scratch_regno): Likewise.
        (ix86_static_chain): Likewise.
        (x86_output_mi_thunk): Likewise.

Test on i686-w64-mingw32.  Ok for apply?

Regards,
Kai

Index: i386.c
===================================================================
--- i386.c	(Revision 193781)
+++ i386.c	(Arbeitskopie)
@@ -9655,6 +9655,8 @@
       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
@@ -9665,10 +9667,15 @@
       if ((regparm < 1 || (fastcall_p && !static_chain_p))
 	  && drap_regno != AX_REG)
 	regno = AX_REG;
-      else if (regparm < 2 && drap_regno != DX_REG)
+      /* 'thiscall' sets regparm to 1, uses ecx for arguments and edx
+	  for the static chain register.  */
+      else if (thiscall_p && !static_chain_p && drap_regno != AX_REG)
+        regno = AX_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))
@@ -11180,12 +11187,15 @@
     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)
@@ -11198,6 +11208,12 @@
 	    }
 	  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))
@@ -25134,7 +25150,7 @@

       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.
@@ -25142,6 +25158,13 @@
 	     leaves us with EAX for the static chain.  */
 	  regno = AX_REG;
 	}
+      else if ((ccvt & IX86_CALLCVT_THISCALL) != 0)
+	{
+	  /* Thiscall functions use ecx for arguments, which leaves
+	     us with EAX and EDX for the static chain.
+	     We are using for abi-compatibility EAX.  */
+	  regno = AX_REG;
+	}
       else if (ix86_function_regparm (fntype, fndecl) == 3)
 	{
 	  /* For regparm 3, we have no free call-clobbered registers in
@@ -34799,8 +34822,10 @@
   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;
     }