
Philips Semiconductors
DSPCPU Operations for TM1300
PRODUCT SPECIFICATION
A-143
prefetch
pseudo-op for prefd(0)
SYNTAX
[ IF r
guard ] pref rsrc1
FUNCTION
if r
guard then {
cache_block_mask = ~(cache_block_size - 1)
data_cache <- mem[(rsrc1 + 0) & cache_block_mask]
}
ATTRIBUTES
Function unit
dmemspec
Operation code
209
Number of operands
1
Modier
-
Modier range
-
Latency
-
Issue slots
5
DESCRIPTION
The pref operation is a pseudo operation transformed by the scheduler into an prefd(0) with the same arguments.
(Note: pseudo operations cannot be used in assembly les.)
The pref operation loads the one full cache block size of memory value from the address computed by ((rsrc1+0) &
cache_block_mask) and stores the data into the data cache. This operation is not guaranteed to be executed. The
prefetch unit will not execute this operation when the data to be prefetched is already in the data cache. A pref
operation will not be executed when the cache is already occupied with 2 cache misses, when the operation is issued.
The pref operation optionally takes a guard, specied in rguard. If a guard is present, its LSB controls the execution
of the prefetch operation. If the LSB of rguard is 1, prefetch operation is executed; otherwise, it is not executed.
EXAMPLES
NOTE: This operation is supported only in TM1000, TM1100 and TM1300 and it is not
guaranteed to be available in future generations of Trimedia products.
Initial Values
Operation
Result
r10 = 0xabcd,
cache_block_size = 0x40
pref r10
Loads a cache line for the address space from
0xabc0 to 0x0xabff from the main memory. If the data
is already in the cache, the operation is not executed.
r10 = 0xabcd, r11 = 0,
cache_block_size = 0x40
IF r11 pref r10
since guard is false, pref operation is not executed
r10 = 0xabff, r11 = 1,
cache_block_size = 0x40
IF r11 pref r10
Loads a cache line for the address space from
0xabc0 to 0x0xabff from the main memory. If the data
is already in the cache, the operation is not executed.
SEE ALSO
pref16x pref32x prefd
prefr allocd allocr allocx
pref