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

[Kai Tietz <ktietz70@googlemail.com>]

Hi,

the following patch adjusts used registers for thiscall-calling
convention thunks, so that there aren't register-collisions.  Issue
was that  thiscall-convention has different register-usage as
regparam, but it wasn't handled.

ChangeLog

2012-11-25  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

--- i386.c	2012-11-24 21:34:57.686148400 +0100
+++ i386.c2	2012-11-24 21:34:42.370272400 +0100
@@ -9655,6 +9655,8 @@ get_scratch_register_on_entry (struct sc
       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 +9667,17 @@ get_scratch_register_on_entry (struct sc
       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)
+        regno = drap_regno != DX_REG ? DX_REG : AX_REG;
+      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 +11189,15 @@ split_stack_prologue_scratch_regno (void
     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 +11210,12 @@ split_stack_prologue_scratch_regno (void
 	    }
 	  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 +25152,7 @@ ix86_static_chain (const_tree fndecl, bo

       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 +25160,12 @@ ix86_static_chain (const_tree fndecl, bo
 	     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 EDX for the static chain.  */
+	  regno = DX_REG;
+	}
       else if (ix86_function_regparm (fntype, fndecl) == 3)
 	{
 	  /* For regparm 3, we have no free call-clobbered registers in
@@ -34799,8 +34823,10 @@ x86_output_mi_thunk (FILE *file,
   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;
     }