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Diffstat (limited to 'llvm/lib/Target/RISCV/RISCVFeatures.td')
| -rw-r--r-- | llvm/lib/Target/RISCV/RISCVFeatures.td | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/llvm/lib/Target/RISCV/RISCVFeatures.td b/llvm/lib/Target/RISCV/RISCVFeatures.td index 2754d78..b4556f6 100644 --- a/llvm/lib/Target/RISCV/RISCVFeatures.td +++ b/llvm/lib/Target/RISCV/RISCVFeatures.td @@ -1906,6 +1906,25 @@ def FeatureForcedAtomics : SubtargetFeature< def HasAtomicLdSt : Predicate<"Subtarget->hasStdExtZalrsc() || Subtarget->hasForcedAtomics()">; +// The RISC-V Unprivileged Architecture - ISA Volume 1 (Version: 20250508) +// [https://docs.riscv.org/reference/isa/_attachments/riscv-unprivileged.pdf] +// in section 13.3. Eventual Success of Store-Conditional Instructions, defines +// _constrained_ LR/SC loops: +// The dynamic code executed between the LR and SC instructions can only +// contain instructions from the base ''I'' instruction set, excluding loads, +// stores, backward jumps, taken backward branches, JALR, FENCE, and SYSTEM +// instructions. Compressed forms of the aforementioned ''I'' instructions in +// the Zca and Zcb extensions are also permitted. +// LR/SC loops that do not adhere to the above are _unconstrained_ LR/SC loops, +// and success is implementation specific. For implementations which know that +// non-base instructions (such as the ''B'' extension) will not violate any +// forward progress guarantees, using these instructions to reduce the LR/SC +// sequence length is desirable. +def FeaturePermissiveZalrsc + : SubtargetFeature< + "permissive-zalrsc", "HasPermissiveZalrsc", "true", + "Implementation permits non-base instructions between LR/SC pairs">; + def FeatureTaggedGlobals : SubtargetFeature<"tagged-globals", "AllowTaggedGlobals", "true", "Use an instruction sequence for taking the address of a global " |