DSP_neg32
4-68
32-Bit Vector Negate
DSP_neg32
Function
void DSP_neg32(int *x, int *r, short nx)
Arguments
x[nx]
Pointer to input data vector 1 of size nx with 32-bit elements.
Must be double-word aligned.
r[nx]
Pointer to output data vector of size nx with 32-bit elements.
Must be double-word aligned.
nx
Number of elements of input and output vectors. Must be a
multiple of 4 and
≥
8.
Description
This function negates the elements of a vector (32-bit elements). The input and
output arrays must not be overlapped except for where the input and output
pointers are exactly equal.
Algorithm
This is the C equivalent of the assembly code without restrictions. Note that
the assembly code is hand optimized and restrictions may apply.
void DSP_neg32(int *x, int *r, short nx)
{
short i;
for(i=nx; i>0; i−−)
*(r++)=−*(x++);
}
Special Requirements
-
nx must be a multiple of 4 and greater than or equal to 8.
-
The arrays x[ ] and r[ ] must be double-word aligned.
Implementation Notes
-
Bank Conflicts: No bank conflicts occur.
-
Interruptibility: The code is interrupt-tolerant but not interruptible.
-
The loop is unrolled twice and pipelined.
Benchmarks
Cycles
nx/2 + 19
Codesize
124 bytes
