TI DSP 28335 asm to read ST1

This is an odd one. I need to test that a bit in the register ST1 is set or clear from C.

.global _readST1
.text

_readST1:
PUSH ST1   ; push ST1 onto stack, SP += 1
MOV AL, *--SP ; copy ST1 into AL, SP -= 1
LRETR

Prototype is:

extern Uint16 readST1(void);