Fix alloca on NT

From-SVN: r11280

gcc/config/rs6000/rs6000.md

@@ -6336,9 +6336,10 @@
   if (DEFAULT_ABI == ABI_NT
       && (GET_CODE (operands[0]) != CONST_INT || INTVAL (operands[0]) > 4096))
     {
-      emit_library_call (gen_rtx (SYMBOL_REF, Pmode, \"__allocate_stack\"), 0,
-			 VOIDmode, 1,
-			 operands[0], Pmode);
+      rtx tmp = gen_reg_rtx (SImode);
+      emit_library_call_value (gen_rtx (SYMBOL_REF, Pmode, \"__allocate_stack\"),
+			       tmp, 0, SImode, 1, operands[0], Pmode);
+      emit_insn (gen_set_sp (tmp));
       DONE;
     }
 
@@ -6363,6 +6364,16 @@
   DONE;
 }")
 
+;; Marker to indicate that the stack pointer was changed under NT in
+;; ways not known to the compiler
+
+(define_insn "set_sp"
+  [(set (reg:SI 1)
+	(unspec [(match_operand:SI 0 "register_operand" "r")] 7))]
+  ""
+  ""
+  [(set_attr "length" "0")])
+
 ;; These patterns say how to save and restore the stack pointer.  We need not
 ;; save the stack pointer at function level since we are careful to
 ;; preserve the backchain.  At block level, we have to restore the backchain