For any load or store that is targeted at a memory region that is marked as transient, the following occurs:
• If the memory access misses in the L1 data cache, the returned cache line is allocated in the L1 data
cache but is marked as transient.
• When the line is evicted from the L1 data cache, the transient hint is passed to the L2 cache so that
the replacement policy will not attempt to retain the line. When the line is subsequently evicted from
the L2 cache, it will bypass the L3 cache entirely.
Non-temporal loads
Non-temporal loads indicate to the caches that the data is likely to be used for only short periods. For
example, when streaming single-use read data that is then discarded. In addition to non-temporal loads,
there are also prefetch-memory (
PRFM
) hint instructions with the
STRM
qualifier.
Non-temporal loads to memory which are designated as Write-Back are treated the same as loads to
Transient memory.
A6.4.2
Internal exclusive monitor
The Cortex-A76 core L1 memory system has an internal exclusive monitor.
This monitor is a 2-state, open and exclusive, state machine that manages Load-Exclusive or Store-
Exclusive accesses and Clear-Exclusive (
CLREX
) instructions. You can use these instructions to construct
semaphores, ensuring synchronization between different processes running on the core, and also between
different cores that are using the same coherent memory locations for the semaphore. A Load-Exclusive
instruction tags a small block of memory for exclusive access. CTR.ERG defines the size of the tagged
block as 16 words, one cache line.
Note
A load/store exclusive instruction is any one of the following:
• In the A64 instruction set, any instruction that has a mnemonic starting with
LDX
,
LDAX
,
STX
, or
STLX
.
• In the A32 and T32 instruction sets, any instruction that has a mnemonic starting with
LDREX
,
STREX
,
LDAEX
, or
STLEX
.
See the
Arm
®
Architecture Reference Manual Armv8, for Armv8-A architecture profile
for more
information about these instructions.
A6 Level 1 memory system
A6.4 L1 data memory system
100798_0300_00_en
Copyright © 2016–2018 Arm Limited or its affiliates. All rights
reserved.
A6-78
Non-Confidential
Summary of Contents for Cortex-A76 Core
Page 4: ......
Page 22: ......
Page 23: ...Part A Functional description ...
Page 24: ......
Page 119: ...Part B Register descriptions ...
Page 120: ......
Page 363: ...Part C Debug descriptions ...
Page 364: ......
Page 401: ...Part D Debug registers ...
Page 402: ......
Page 589: ...Part E Appendices ...
Page 590: ......