Translating C Code To Linear Assembly - Texas Instruments TMS320C6000 Programmer's Manual

Redundant Load Elimination

6.11.2 Translating C Code to Linear Assembly

Example 6–62. Linear Assembly for FIR Inner Loop
LDH
LDH
MPY
MPY
ADD
ADD
LDH
LDH
MPY
MPY
ADD
ADD
[ctr] SUB
[ctr] B
6-112
Example 6–62 shows the linear assembly that perform the inner loop of the
FIR filter C code.
Element x0 is read by the MPY p00 before it is loaded by the LDH x0 instruc-
tion; x[j] (the first x0) is loaded outside the loop, but successive even elements
are loaded inside the loop.
.D2 *x_1++[2],x1
.D1 *h++[2],h0
.M1 x0,h0,p00
.M1X x1,h0,p10
.L1 p00,sum0,sum0
.L2X p10,sum1,sum1
.D1 *x++[2],x0
.D2 *h_1++[2],h1
.M2 x1,h1,p01
.M2X x0,h1,p11
.L1X p01,sum0,sum0
.L2 p11,sum1,sum1
.S2 ctr,1,ctr
.S2 LOOP
; x1 = x[j+i+1]
; h0 = h[i]
; x0 * h0
; x1 * h0
; sum0 += x0 * h0
; sum1 += x1 * h0
; x0 = x[j+i+2]
; h1 = h[i+1]
; x1 * h1
; x0 * h1
; sum0 += x1 * h1
; sum1 += x0 * h1
; decrement loop counter
; branch to loop