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Drop __riscv_vendor_feature_bits #101

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Feb 27, 2025
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Drop __riscv_vendor_feature_bits #101

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9 changes: 2 additions & 7 deletions src/c-api.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -839,7 +839,7 @@ This feature is activated by the `target_version/target_clones` function attribu

=== Extension Bitmask

The Extension Bitmask is used to probe whether features are enabled during runtime. This is achieved through three bitmask structures: `__riscv_feature_bits` for standard extensions, `__riscv_vendor_feature_bits` for vendor-specific extensions and `__riscv_cpu_model` for the CPU model. Additionally, `__init_riscv_feature_bits` is used to update the contents of these structures according to the system configuration.
The Extension Bitmask is used to probe whether features are enabled during runtime. This is achieved through three bitmask structures: `__riscv_feature_bits` for standard extensions and `__riscv_cpu_model` for the CPU model. Additionally, `__init_riscv_feature_bits` is used to update the contents of these structures according to the system configuration.

The bitmask structures use the following definitions:

Expand All @@ -849,11 +849,6 @@ struct {
unsigned long long features[];
} __riscv_feature_bits;

struct {
unsigned length;
unsigned long long features[];
} __riscv_vendor_feature_bits;

struct {
unsigned mvendorid;
unsigned long long marchid;
Expand All @@ -873,7 +868,7 @@ To initiate these structures based on the system's extension status, the followi
void __init_riscv_feature_bits(void *);
```

The `__init_riscv_feature_bits` function updates `length`, `mvendorid`, `marchid`, `mimpid` and the `features` in `__riscv_feature_bits` and `__riscv_vendor_feature_bits` according to the enabled extensions in the system.
The `__init_riscv_feature_bits` function updates `length`, `mvendorid`, `marchid`, `mimpid` and the `features` in `__riscv_feature_bits` according to the enabled extensions in the system.

The `__init_riscv_feature_bits` function accepts an argument of type `void *`. This argument allows the platform to provide pre-computed data and access it without additional effort. For example, Linux could pass the vDSO object to avoid an extra system call.

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