# Vault 7: Projects

This publication series is about specific projects related to the Vault 7 main publication.

### Protego

# MPLAB XC16 C-Compiler

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Built-in Functions
 2012-2013 Microchip Technology Inc. DS50002071C-page 303
__builtin_clr_prefetch
Description: Clear an accumulator and prefetch 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 x_memory_buffer[256]
__attribute__((space(xmemory)));
int y_memory_buffer[256]
__attribute__((space(ymemory)));
int *xmemory;
int *ymemory;
int awb;
int xVal, yVal;
xmemory = x_memory_buffer;
ymemory = y_memory_buffer;
result = __builtin_clr(&xmemory, &xVal, 2,
&ymemory, &yVal, 2, &awb, B);
might generate:
clr A, [w8]+=2, w4, [w10]+=2, w5, w13
The compiler may need to spill w13 to ensure that it is available for the write-back. It may be
recommended to users that the register be claimed for this purpose.
After this instruction:
 result will be cleared
 xVal will contain x_memory_buffer[0]
 yVal will contain y_memory_buffer[0]
 xmemory and ymemory will be incremented by 2, ready for the next mac operation
Prototype: int __builtin_clr_prefetch(
int **xptr, int *xval, int xincr,
int **yptr, int *yval, int yincr, int *AWB,
int AWB_accum);
Argument: xptr Integer pointer to x prefetch.
xval Integer value of x prefetch.
xincr Integer increment value of x prefetch.
yptr Integer pointer to y prefetch.
yval Integer 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:
clr
Error Messages An error message will be displayed if:
 the result 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 and AWB is not null

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