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Rework the extension test macros section #57

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Feb 1, 2024
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Rework the extension test macros section #57

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47 changes: 17 additions & 30 deletions riscv-c-api.md
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Expand Up @@ -108,15 +108,25 @@ Perhaps obvious, but these are mutually exclusive, so only one is defined at a t
for a compilation unit.


### Architecture Extension Test Macro
### Architecture Extension Test Macros

Architecture extension test macro is a new set of test macro to checking the
availability and version for certain extension, however not all compilers are
supported, so you should check `__riscv_arch_test` to make sure this compiler
is supporting those preprocessor definitions.
Architecture extension test macros allow checking the availability and version
of extensions at compile-time. These feature macros are optional, and compilers
that support them provide a `__riscv_arch_test` macro (with the value `1`).

The value of architecture extension test macro are defined as its version,
which is compute by following formula:
The naming rule for the test macros is `__riscv_<ext_name>`,
where `<ext_name>` is all lower-case. Examples:
- The test macro for the `A` extension is `__riscv_a`.
- The test macro for the `Zifencei` extension is `__riscv_zifencei`.
- The test macro for the `XVentanaCondOps` extension is `__riscv_xventantacondops`.

Besides extensions, test macros also exist for ISA bases following the same pattern.
Examples:
- The test macro for the `I` base is `__riscv_i`.
- The test macro for the `E` base is `__riscv_e`.

The value of the test macros is derived from its version using the following
formula:

```
<MAJOR_VERSION> * 1,000,000 + <MINOR_VERSION> * 1,000 + <REVISION_VERSION>
Expand All @@ -125,29 +135,6 @@ which is compute by following formula:
For example:
- F-extension v2.2 will define `__riscv_f` as `2002000`.

| Name | Value | When defined |
| ----------------------- | ------------ | ----------------------------- |
| __riscv_arch_test | 1 | Defined if compiler support new architecture extension test macro. |
| __riscv_i | Arch Version | `I` extension is available. |
| __riscv_e | Arch Version | `E` extension is available. |
| __riscv_m | Arch Version | `M` extension is available. |
| __riscv_a | Arch Version | `A` extension is available. |
| __riscv_f | Arch Version | `F` extension is available. |
| __riscv_d | Arch Version | `D` extension is available. |
| __riscv_q | Arch Version | `Q` extension is available. |
| __riscv_c | Arch Version | `C` extension is available. |
| __riscv_p | Arch Version | `P` extension is available. |
| __riscv_v | Arch Version | `V` extension is available. |
| __riscv_zicsr | Arch Version | `Zicsr` extension is available. |
| __riscv_zifencei | Arch Version | `Zifencei` extension is available. |
| __riscv_zawrs | Arch Version | `Zawrs` extension is available. |
| __riscv_zba | Arch Version | `Zba` extension is available. |
| __riscv_zbb | Arch Version | `Zbb` extension is available. |
| __riscv_zbc | Arch Version | `Zbc` extension is available. |
| __riscv_zbs | Arch Version | `Zbs` extension is available. |
| __riscv_zfh | Arch Version | `Zfh` extension is available. |
| __riscv_zimop | Arch Version | `Zimop` extension is available. |

### ABI Related Preprocessor Definitions

| Name | Value | When defined |
Expand Down