w64: Fix TCG helper functions with 5 arguments

TCG uses 6 registers for function arguments on 64 bit Linux hosts,
but only 4 registers on W64 hosts.

Commit 2999a0b2 increased the number
of arguments for some important helper functions from 4 to 5
which triggered a bug for W64 hosts: QEMU aborts when executing
helper_lcall_real in the guest's BIOS because function
tcg_target_get_call_iarg_regs_count always returned 6.

As W64 has only 4 registers for arguments, the 5th argument must be
passed on the stack using a correct stack offset.
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

tcg/i386/tcg-target.c

@@ -118,7 +118,7 @@ static void patch_reloc(uint8_t *code_ptr, int type,
 static inline int tcg_target_get_call_iarg_regs_count(int flags)
 {
     if (TCG_TARGET_REG_BITS == 64) {
-        return 6;
+        return ARRAY_SIZE(tcg_target_call_iarg_regs);
     }
 
     return 0;

tcg/i386/tcg-target.h

@@ -67,7 +67,11 @@ typedef enum {
 /* used for function call generation */
 #define TCG_REG_CALL_STACK TCG_REG_ESP 
 #define TCG_TARGET_STACK_ALIGN 16
+#if defined(_WIN64)
+#define TCG_TARGET_CALL_STACK_OFFSET 32
+#else
 #define TCG_TARGET_CALL_STACK_OFFSET 0
+#endif
 
 /* optional instructions */
 #define TCG_TARGET_HAS_div2_i32         1