Hello, I am writing for a question regarding the C2000 DSP C compiler
(Code Composer Studio 8.0.0.00016, Compiler version 21.6.0.LTS, DSP TMS320F28375S).
Here are two examples of translation, in which:
acc 32 bit unsigned (DSP accumulator)
res 16 bit unsigned local variable
1) C code acc += (((Uint16)(acc >> 16)) << 4);
res = acc + 1;
ASM code ADD ACC,AH<<#4 ; SXM = 0
expected ADD ACC,#1
MOV PL,AL
ASM code MOVL P,ACC
from compiler MOV ACC,PH << #4
MOVZ AR7,AL
MOVL ACC,P
ADDU ACC,AR7
MOVL P,ACC
MOV AL,PL
ADDB AL,#1
MOV PL,AL
2) C code res = acc + (((Uint16)(acc >> 16)) << 4) +1;
ASM code ADD ACC,AH<<#4 ; SXM = 0
expected ADD ACC,#1
MOV PL,AL
ASM code MOVZ AR4,AL
from compiler MOV ACC,AH << #4
ADD AR4,AL
ADDB XAR4,#1
The ASM code from compiler of example 2 is not the expected code (ie what I would have written), but it is still acceptable.
In example 1, however, the compiler produces three times the number of assembly instructions compared to the expected code.
Am I doing something wrong ?
Are there any guidelines for writing C code so that the assembly code produced by the compiler is efficient?
Thank you!
Good afternoon
