Function attribute for standard fixed-length vector calling convention variant #68
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…n variant Fixed-length vector are passed via general purposed register or memory within current ABI design, we proposed a standard fixed-length vector calling convention variant for passing the fixed-length vector via vector register. This is the syntax part in the proposal, further detail for that calling convention variant see riscv-non-isa/riscv-elf-psabi-doc#418
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Stylistically, since this is a well-defined RISC-V specific ABI attribute independent of any GNU extensions, I wonder if it should be I believe that this needs to be included in C++ function pointer mangling to support natural uses (although this doesn't work on aarch64). Do the rules for that need to be specified here? LGTM otherwise. |
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@sorear thanks for remind that, I almost forgot |
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Update:
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cmuellner
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cmuellner
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| The attribute can accept an optional unsigned integer argument within the value | ||
| range of `[32, 65536]`, which must be a power of two. This argument specifies | ||
| the `ABI_VLEN`. If not provided, the default value is set to 128. However, this | ||
| default value can be changed via command-line options or pragma directives. |
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Where are the command line options or pragma defined?
| // foo is declared to use the standard fixed-length vector calling convention variant | ||
| // with ABI_VLEN=256. Compilation will succeed with -march=rv64gcv_zvl256b, as it | ||
| // supports VLEN of 256. However, compiling with -march=rv64gcv will result in an error, | ||
| // because rv64gcv's VLEN is 128, which is less than the specified ABI_VLEN of 256. |
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This disagrees with the preceding paragraph that says ABI_VLEN must be larger or equal than the minimval VLEN.
| void bar __attribute__((riscv_vls_cc(256))); | ||
| ``` | ||
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| One constraint on `ABI_VLEN` is that it must be larger than or equal to the |
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"ABI_VLEN must be less than or equal to`." No need for the "One constraint on".
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| The attribute can accept an optional unsigned integer argument within the value | ||
| range of `[32, 65536]`, which must be a power of two. This argument specifies | ||
| the `ABI_VLEN`. If not provided, the default value is set to 128. However, this |
…n variant
Fixed-length vector are passed via general purposed register or memory within current ABI design, we proposed a standard fixed-length vector calling convention variant for passing the fixed-length vector via vector register.
This is the syntax part in the proposal, further detail for that calling convention variant see riscv-non-isa/riscv-elf-psabi-doc#418