Vault 7: Projects
This publication series is about specific projects related to the Vault 7 main publication.
Built-in Functions
2012-2013 Microchip Technology Inc. DS50002071C-page 311
__builtin_mac
Description: Computes a x b and sums with accumulator; also prefetches data ready for a future MAC
operation.
xptr may be null to signify no X prefetch to be performed, in which case the values of
xincr and xval are ignored, but required.
yptr may be null to signify no Y prefetch to be performed, in which case the values of
yincr and yval are ignored, but required.
xval and yval nominate the address of a C variable where the prefetched value will be
stored.
xincr and yincr may be the literal values: -6, -4, -2, 0, 2, 4, 6 or an integer value.
If AWB is non null, the other accumulator will be written back into the referenced variable.
For example:
volatile register int result asm("A");
volatile register int B asm("B");
int *xmemory;
int *ymemory;
int xVal, yVal;
result = __builtin_mac(result, xVal, yVal,
&xmemory, &xVal, 2,
&ymemory, &yVal, 2, 0, B);
might generate:
mac w4*w5, A, [w8]+=2, w4, [w10]+=2, w5
Prototype: int __builtin_mac(int Accum, int a, int b,
int **xptr, int *xval, int xincr,
int **yptr, int *yval, int yincr, int *AWB,
int AWB_accum);
Argument: Accum Accumulator to sum.
a Integer multiplicand.
b Integer multiplier.
xptr Integer pointer to pointer to x prefetch.
xval Integer pointer to value of x prefetch.
xincr Integer increment value of x prefetch.
yptr Integer pointer to pointer to y prefetch.
yval Integer pointer to value of y prefetch.
yincr Integer increment value of y prefetch.
AWB Accumulator write-back location.
AWB_accum Accumulator to write-back.
Return Value: Returns the cleared value result to an accumulator.
Assembler Operator/
Machine Instruction:
mac
Error Messages An error message will be displayed if:
the result is not an accumulator register
Accum is not an accumulator register
xval is a null value but xptr is not null
yval is a null value but yptr is not null
AWB_accum is not an accumulator register and AWB is not null
Protego_Release_01_05-Related-OEM-Documentation-MPLAB-XC16-C-Compiler.pdf