example 3-29.sa

《基于TI DSP的通用算法实现》程序代码

; Example 3 - 29. Autoscaling SA Listing of DIT Radix-4 FFT for the TMS320C62x DSP


test_bit_growth: .trip 16
		ldw 	*+p_x[j], tmp
		norm 	tmp, xtmph 		; test for redundant sign bit of HI half
		shl 	tmp, 16, xtmpl
		norm 	xtmpl, xtmpl 		; test for redundant sign bit of LO half
		cmplt 	xtmph, exp, tmp 	; test if bit grow
  [tmp]add 	xtmph, 0, exp
		cmplt 	xtmpl, exp, tmp 	; test if bit grow
  [tmp]add 	xtmpl, 0, exp
		cmpgt 	exp, 2, tmp 		; if exp>2 than no scaling
  [tmp]b 		no_scale
		cmpeq 	exp, 0, tmp 		; compare if bit grow 3 bits
  [tmp]sub 	3, exp, t0 		; calculate shift
  [tmp]mvk 	0x0213, t1 		; csta & cstb to ext xtmpl
  [tmp]add 	scale, t0, scale	; accumulate scale
  [tmp]b 		scaling
		cmpeq 	exp, 1, tmp 		; compare if bit grow 2 bit
  [tmp]sub 	3, exp, t0
  [tmp]mvk 	0x0212, t1 		; csta & cstb to ext xtmpl
  [tmp]add 	scale, t0, scale 	; accumulate scale
  [tmp]b 		scaling
		sub 	3, exp, t0 		; grows 1 bit
		mvk 	0x0211, t1 		; csta & cstb to ext xtmpl
		add 	scale, t0, scale	; accumulate scale
		b 		scaling
no_scale:
		add 	j, 1, j
		cmplt 	j, n, tmp 			; compare if test all output
  [tmp]b 		test_bit_growth 	; if not, test next output
		b 		next_stage 		; else go to next stage
scaling:
		zero 	j
scaling_loop: .trip 16
		ldw 	*+p_x[j], tmp
		shr 	tmp, t0, xtmph 		; scaling HI half
		and 	xtmph, mskh, xtmph 	; mask HI half
		ext 	tmp, t1, xtmpl 		; scaling LO half
		and 	xtmpl, t2, xtmpl 	; mask LO half by 0x0000ffff
		or 		xtmph, xtmpl, tmp 	; x[j]=[xtmph | xtmpl]
		stw	 	tmp, *+p_x[j]
		add 	j, 1, j
		cmplt 	j, n, tmp
  [tmp]b 		scaling_loop
next_stage:
		shl 	ie, 2, ie
		shr 	k, 2, k
		b 		stage_loop 			; end of stage loop