py: Put define of x86 argument registers in asmx86.h.

py/asmx86.c

@@ -496,13 +496,13 @@ void asm_x86_call_ind(asm_x86_t *as, void *ptr, mp_uint_t n_args, int temp_r32)
     // TODO align stack on 16-byte boundary before the call
     assert(n_args <= 3);
     if (n_args > 2) {
-        asm_x86_push_r32(as, REG_ARG_3);
+        asm_x86_push_r32(as, ASM_X86_REG_ARG_3);
     }
     if (n_args > 1) {
-        asm_x86_push_r32(as, REG_ARG_2);
+        asm_x86_push_r32(as, ASM_X86_REG_ARG_2);
     }
     if (n_args > 0) {
-        asm_x86_push_r32(as, REG_ARG_1);
+        asm_x86_push_r32(as, ASM_X86_REG_ARG_1);
     }
 #ifdef __LP64__
     // We wouldn't run x86 code on an x64 machine.  This is here to enable

py/asmx86.h

@@ -44,6 +44,14 @@
 #define REG_ESI (6)
 #define REG_EDI (7)
 
+// x86 passes values on the stack, but the emitter is register based, so we need
+// to define registers that can temporarily hold the function arguments.  They
+// need to be defined here so that asm_x86_call_ind can push them onto the stack
+// before the call.
+#define ASM_X86_REG_ARG_1 REG_EAX
+#define ASM_X86_REG_ARG_2 REG_ECX
+#define ASM_X86_REG_ARG_3 REG_EDX
+
 // condition codes, used for jcc and setcc (despite their j-name!)
 #define ASM_X86_CC_JB  (0x2) // below, unsigned
 #define ASM_X86_CC_JZ  (0x4)

py/emitnative.c

@@ -200,9 +200,9 @@ STATIC byte mp_f_n_args[MP_F_NUMBER_OF] = {
 #define EXPORT_FUN(name) emit_native_x86_##name
 
 #define REG_RET REG_EAX
-#define REG_ARG_1 REG_EAX
+#define REG_ARG_1 ASM_X86_REG_ARG_1
-#define REG_ARG_2 REG_ECX
+#define REG_ARG_2 ASM_X86_REG_ARG_2
-#define REG_ARG_3 REG_EDX
+#define REG_ARG_3 ASM_X86_REG_ARG_3
 
 // caller-save, so can be used as temporaries
 #define REG_TEMP0 REG_EAX