[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

wangpc-pp wrote: > Can we split the CodeGen part out of this patch? MC part is https://github.com/llvm/llvm-project/pull/78970. This PR will be the CodeGen part and I will update this PR later. https://github.com/llvm/llvm-project/pull/77424 ___

[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

topperc wrote: > > I guess Zaamo + Zacas is technically a way one could implement atomics > > without LR/SC? > > The Zacas extension depends upon the A extension. I filed an issue asking about that https://github.com/riscv/riscv-zaamo-zalrsc/issues/5

[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

dtcxzyw wrote: > I guess Zaamo + Zacas is technically a way one could implement atomics > without LR/SC? The Zacas extension depends upon the A extension. https://github.com/llvm/llvm-project/pull/77424 ___ cfe-commits mailing list

[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

jrtc27 wrote: I guess Zaamo + Zacas is technically a way one could implement atomics without LR/SC? https://github.com/llvm/llvm-project/pull/77424 ___ cfe-commits mailing list cfe-commits@lists.llvm.org

[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

asb wrote: Thanks James, that matches what I'd understood. Just one comment on this though: > If Zaamo is present, but neither Zalrsc nor Zacas are present, I think > there's no way to implement a cmpxchg operation. This means lock-free atomics > cannot be supported, so it should

[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

jyknight wrote: There's two sets of atomic functions: `__atomic_*` are provided by libatomic, and might use locking, or not. `__sync_*` should always be lock-free. These are only used on certain architectures where it's guaranteed that the operation _can_ be implemented lock-free, but it's

[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

asb wrote: CC @jyknight who can hopefully confirm if my interpretation is correct. Based on your comment on #77814, perhaps the expectation is that libatomic would have a lock-free implementation for any __sync calls used up to the max atomic width (e.g. lr/sc based if there's no AMO

[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

@@ -0,0 +1,11 @@ +# RUN: not llvm-mc -triple riscv32 -mattr=+experimental-zaamo < %s 2>&1 | FileCheck %s dtcxzyw wrote: Can we split `rv32a-invalid.s` into two files? I think it is better than duplicating tests for new extensions.

[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

llvmbot wrote: @llvm/pr-subscribers-clang @llvm/pr-subscribers-mc Author: Wang Pengcheng (wangpc-pp) Changes `A` extension has been split into two parts: Zaamo (Atomic Memory Operations) and Zalrsc (Load-Reserved/Store-Conditional). See also https://github.com/riscv/riscv-zaamo-zalrsc.