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arm: sve_addvl test program that prints sve length

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Ciro Santilli 六四事件 法轮功
2019-10-30 22:00:02 +00:00
parent 37b93ecfbb
commit 02018daa95
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@@ -16219,7 +16219,9 @@ There are analogous LD3 and LD4 instruction.
Scalable Vector Extension.
Example: link:userland/arch/aarch64/sve.S[]
Examples:
* link:userland/arch/aarch64/sve.S[]
To understand it, the first thing you have to look at is the execution example at Fig 1 of: https://alastairreid.github.io/papers/sve-ieee-micro-2017.pdf
@@ -16244,6 +16246,41 @@ SVE support is indicated by `ID_AA64PFR0_EL1.SVE` which is dumped from link:bare
Using SVE normally requires setting the CPACR_EL1.FPEN and ZEN bits, which as as of lkmc 29fd625f3fda79f5e0ee6cac43517ba74340d513 + 1 we also enable in our <<baremetal-bootloaders>>, see also: <<aarch64-baremetal-neon-setup>>.
===== ARM SVE VADDL instruction
Get the SVE vector length. The following programs do that and print it to stdout:
* link:userland/arch/aarch64/inline_asm/sve_addvl.c[]
* link:userland/arch/aarch64/sve_addvl.S[]
===== Change ARM SVE vector length in emulators
gem5 covered at: https://stackoverflow.com/questions/57692765/how-to-change-the-gem5-arm-sve-vector-length
It is fun to observe this directly with the <<arm-sve-vaddl-instruction>> in SE:
....
./run --arch aarch64 --userland userland/arch/aarch64/sve_addvl.S --static --emulator gem5 -- --param 'system.cpu[:].isa[:].sve_vl_se = 1'
./run --arch aarch64 --userland userland/arch/aarch64/sve_addvl.S --static --emulator gem5 -- --param 'system.cpu[:].isa[:].sve_vl_se = 2'
./run --arch aarch64 --userland userland/arch/aarch64/sve_addvl.S --static --emulator gem5 -- --param 'system.cpu[:].isa[:].sve_vl_se = 4'
....
which consecutively:
....
0x0000000000000080
0x0000000000000100
0x0000000000000200
....
which are multiples of 128.
TODO how to set it on QEMU at runtime? As of LKMC 37b93ecfbb5a1fcbd0c631dd0b42c5b9f2f8a89a + 1 QEMU outputs:
....
0x0000000000000800
....
===== SVE bibliography
* https://www.rico.cat/files/ICS18-gem5-sve-tutorial.pdf step by step of a complete code execution examples, the best initial tutorial so far