3 ms·

LoCs of aarch64 vs risc-v is comical. I wonder what's going on there.

by snvzz 4y ago

ghotli 4y ago
I'm no expert (but I do work with this stuff regularly) and I realize this is gcc documentation vs llvm docs. Regardless, arm32/64 has a lot of optional instruction sets that may or may not be supported on a given processor as improvements have been made over time. For example, check out the feature modifiers at the bottom of the page here for aarch64: https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/AArch64-Options.html#AArch64-Options https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/AArch64-Option... Versus RISC-V: https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/RISC-V-Options.html#RISC-V-Options https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/RISC-V-Options... Arm32 is even more complex: https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/ARM-Options.html#ARM-Options https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/ARM-Options.ht...
drew-y 4y ago
Where are you making this comparison from? Edit. Never mind. Found it. https://github.com/MPACT-ORG/llvm-project/blob/work/llvm/docs/Mdl/MachineDescriptionNotes.md#upstream-targets https://github.com/MPACT-ORG/llvm-project/blob/work/llvm/doc... RISC-V: 104 LoC, AArch64: 3483. That's wild.
- tmd83 4y ago
  Then there's x86: 7406 LoC
KZerda 4y ago
Number of variants to a large extent. Risc-V has a relatively few number of implementations that are about the same in terms of how they implement things. Aarch64 has a comparably huge number of implementations that have different pipeline descriptions, different extension APIs supported, etc. Aarch64 includes descriptors for everything from a low-end Cortex A53 designed back in 2012 to a a high-end Apple M2 that was released this year.
Ericson2314 4y ago
Born RISC, Died CISC Will happen to RISC-V too, dontcha worry ;)
- snvzz 4y ago
  Nah. RISC-V is already caught up with the important features x86 and ARM have, and still hasn't been corrupted. It'll endure.
  - Ericson2314 4y ago
    I hope! Opt-in special extensions CISC (versus exposing one special customer's thing to everyone) is also less bad.

LoCs of aarch64 vs risc-v is comical. I wonder what's going on there.

by snvzz 4y ago

LoCs of aarch64 vs risc-v is comical. I wonder what's going on there.

I'm no expert (but I do work with this stuff regularly) and I realize this is gcc documentation vs llvm docs. Regardless, arm32/64 has a lot of optional instruction sets that may or may not be supported on a given processor as improvements have been made over time. For example, check out the feature modifiers at the bottom of the page here for aarch64: https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/AArch64-Options.html#AArch64-Options https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/AArch64-Option... Versus RISC-V: https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/RISC-V-Options.html#RISC-V-Options https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/RISC-V-Options... Arm32 is even more complex: https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/ARM-Options.html#ARM-Options https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/ARM-Options.ht...

drew-y 4y ago

Where are you making this comparison from? Edit. Never mind. Found it. https://github.com/MPACT-ORG/llvm-project/blob/work/llvm/docs/Mdl/MachineDescriptionNotes.md#upstream-targets https://github.com/MPACT-ORG/llvm-project/blob/work/llvm/doc... RISC-V: 104 LoC, AArch64: 3483. That's wild.

tmd83 4y ago
Then there's x86: 7406 LoC

KZerda 4y ago

Number of variants to a large extent. Risc-V has a relatively few number of implementations that are about the same in terms of how they implement things. Aarch64 has a comparably huge number of implementations that have different pipeline descriptions, different extension APIs supported, etc. Aarch64 includes descriptors for everything from a low-end Cortex A53 designed back in 2012 to a a high-end Apple M2 that was released this year.

Ericson2314 4y ago

Born RISC, Died CISC Will happen to RISC-V too, dontcha worry ;)

snvzz 4y ago
Nah. RISC-V is already caught up with the important features x86 and ARM have, and still hasn't been corrupted. It'll endure.
- Ericson2314 4y ago
  I hope! Opt-in special extensions CISC (versus exposing one special customer's thing to everyone) is also less bad.