Under translator under C2Rust Transpile (main_function.rs + sims.rs)
Retriever7 min read
! This module provides translation for SIMD operations and expressions.
simd.rs
pub fn convert_shuffle_vector: 此公共函数的目标是将 shuffle 操作转换为相应的 Rust SIMD 库调用。该函数首先检查输入参数的个数是否符合预期。如果不符合预期，函数将返回错误。接着，它对两个输入向量进行处理，如果这两个向量的类型或长度不同，同样会返回错误。最后，根据各种条件选择合适的 shuffle 函数，然后调用它。fn strip_vector_explicit_cast: 这个私有函数的目标是移除明确的向量转换。在一些情况下，向量在内部类型之间转换可能导致问题，尤其是在 shuffle 向量的情况下，这些 shuffle 向量通常是在内建调用上的宏。这个函数就是去除这些转换以简化代码和提高可读性。fn get_shuffle_vector_mask: 这个私有函数的目标是从 shuffle 向量的“超级内建”调用中获取 mask 表达式。这些表达式包含应用于 mask 表达式的数学偏移（或者是数值常量），我们希望提取这个 mask。pub fn casting_simd_builtin_call: 这个公共函数的目标是确定是否对 SIMD 调用值进行了转换，因为内建定义会为我们的目的添加多余的转换。函数检查表达式的类型，如果表达式是对 SIMD 的调用并且进行了明确的转换，那么函数将返回 true，否则返回 false。
#![deny(missing_docs)]
//! This module provides translation for SIMD operations and expressions.
// Various imports
use super::*;
use crate::c_ast::BinOp::{Add, BitAnd, ShiftRight};
use crate::c_ast::CExprKind::{Binary, Call, Conditional, ExplicitCast, ImplicitCast, Literal};
use crate::c_ast::CLiteral::Integer;
use crate::c_ast::CTypeKind::{Char, Double, Float, Int, LongLong, Short};
use crate::c_ast::CastKind::{BitCast, IntegralCast};
// This is a list of SIMD functions which were not available in Rust as of version 1.29
static MISSING_SIMD_FUNCTIONS: [&str; 36] = [
//...
];
// List of SIMD functions that are specific to the x86_64 architecture
static SIMD_X86_64_ONLY: &[&str] = &[
//...
];
// Function that adds a use statement for a given item within a specific architecture
fn add_arch_use(store: &mut ItemStore, arch_name: &str, item_name: &str) {
store.add_use_with_attr(
vec!["core".into(), "arch".into(), arch_name.into()],
item_name,
mk().meta_item_attr(
AttrStyle::Outer,
mk().meta_list(
"cfg",
vec![NestedMeta::Meta(
mk().meta_namevalue("target_arch", arch_name),
)],
),
)
.pub_(),
);
}
// This is the primary implementation for the translation of SIMD in the code
impl<'c> Translation<'c> {
// Checks if a given typedef name corresponds to a SIMD type
pub fn import_simd_typedef(&self, name: &str) -> TranslationResult<bool> {
Ok(match name {
// Handles known SIMD typedefs
"__m128i" | "__m128" | "__m128d" | "__m64" | "__m256" | "__m256d" | "__m256i" => {
// __m64 and MMX support were removed from upstream Rust.
if name == "__m64" {
return Err(format_err!(
"__m64 and MMX are no longer supported, due to removed upstream support. See https://github.com/immunant/c2rust/issues/369"
).into());
}
// Add use statements for the x86 and x86_64 architectures
self.with_cur_file_item_store(|item_store| {
add_arch_use(item_store, "x86", name);
add_arch_use(item_store, "x86_64", name);
});
true
}
// These are C internal types and don't need explicit support
"__v1di"
| "__v2si"
| "__v4hi"
//...
=> true,
_ => false,
})
}
}
/// 判断特定的函数名是否为 SIMD 基元。如果是，将会生成相应的 use 语句，并返回 `true`，
/// 因此无需进一步处理。
pub fn import_simd_function(&self, name: &str) -> TranslationResult<bool> {
if name.starts_with("_mm") {
// REVIEW: 这将在所有 SIMD 函数中进行线性查找。可以使用懒惰静态哈希集
if MISSING_SIMD_FUNCTIONS.contains(&name) {
return Err(format_err!(
"SIMD 函数 {} 目前没有对应的 Rust 函数",
name
)
.into());
}
// 大部分 x86/64 SIMD 是稳定的，但仍有一些被特性门控限制。
self.use_feature("stdsimd");
self.with_cur_file_item_store(|item_store| {
// REVIEW: 也是线性查找
if !SIMD_X86_64_ONLY.contains(&name) {
add_arch_use(item_store, "x86", name);
}
add_arch_use(item_store, "x86_64", name);
});
Ok(true)
} else {
Ok(false)
}
}
/// 该函数将删除一个隐式转换的 int 或显式转换的 vector，因为对于我们的目的而言，
/// 这两种转换都是不必要的（且可能带来问题）
fn clean_int_or_vector_param(&self, expr_id: CExprId) -> CExprId {
match self.ast_context[expr_id].kind {
// 出于某种原因，这里似乎有一个错误的隐式转换为 char
// 可能是内置函数接受一个 char，即使函数接受一个 int
ImplicitCast(_, expr_id, IntegralCast, _, _) => expr_id,
// (internal)(external)(vector input)
ExplicitCast(qty, _, BitCast, _, _) => {
if let CTypeKind::Vector(..) = self.ast_context.resolve_type(qty.ctype).kind {
let (_, stripped_expr_id, _) = self.strip_vector_explicit_cast(expr_id);
stripped_expr_id
} else {
expr_id
}
}
_ => expr_id,
}
}
/// 基于内置函数生成对 Rust SIMD 函数的调用。Clang 6 只支持其中一个，
/// 但 Clang 7 转换了更多的 "super builtins"
pub fn convert_simd_builtin(
&self,
ctx: ExprContext,
fn_name: &str,
args: &[CExprId],
) -> TranslationResult<WithStmts<Box<Expr>>> {
self.import_simd_function(fn_name)?;
let mut processed_args = vec![];
let (_, first_expr_id, _) = self.strip_vector_explicit_cast(args[0]);
processed_args.push(first_expr_id);
processed_args.extend(
args[1..]
.iter()
.map(|arg| self.clean_int_or_vector_param(*arg)),
);
let param_translation = self.convert_exprs(ctx.used(), &processed_args)?;
param_translation.and_then(|call_params| {
let call = mk().call_expr(mk().ident_expr(fn_name), call_params);
if ctx.is_used() {
Ok(WithStmts::new_val(call))
} else {
Ok(WithStmts::new(
vec![mk().semi_stmt(call)],
self.panic_or_err("No value for unused shuffle vector return"),
))
}
})
}
/// 生成一个零值，用于初始化给定的向量类型。类型是由底层元素类型和向量中的元素数量指定的。
pub fn implicit_vector_default(
&self,
ctype: CTypeId,
len: usize,
is_static: bool,
) -> TranslationResult<WithStmts<Box<Expr>>> {
// 注意：这只适用于 x86/_64，因此其他架构可能需要某种方式的消歧义导出
let (fn_name, bytes) = match (&self.ast_context[ctype].kind, len) {
(Float, 4) => ("_mm_setzero_ps", 16),
(Float, 8) => ("_mm256_setzero_ps", 32),
(Double, 2) => ("_mm_setzero_pd", 16),
(Double, 4) => ("_mm256_setzero_pd", 32),
(Char, 16) | (Int, 4) | (LongLong, 2) => ("_mm_setzero_si128", 16),
(Char, 32) | (Int, 8) | (LongLong, 4) => ("_mm256_setzero_si256", 32),
(Char, 8) | (Int, 2) | (LongLong, 1) => {
// __m64 在 rust 1.29 时仍然是不稳定的
self.use_feature("stdsimd");
("_mm_setzero_si64", 8)
}
(kind, len) => {
return Err(format_err!(
"不支持的向量默认初始化器: {:?} x {}",
kind,
len
)
.into())
}
};
if is_static {
let zero_expr = mk().lit_expr(mk().int_lit(0, "u8"));
let n_bytes_expr = mk().lit_expr(mk().int_lit(bytes, ""));
let expr = mk().repeat_expr(zero_expr, n_bytes_expr);
Ok(WithStmts::new_unsafe_val(transmute_expr(
mk().infer_ty(),
mk().infer_ty(),
expr,
)))
} else {
self.import_simd_function(fn_name)
.expect("None of these fns should be unsupported in rust");
Ok(WithStmts::new_val(
mk().call_expr(mk().ident_expr(fn_name), Vec::new()),
))
}
}
/// 转换对应向量类型的列表初始化器。
pub fn vector_list_initializer(
&self,
ctx: ExprContext,
ids: &[CExprId],
ctype: CTypeId,
len: usize,
) -> TranslationResult<WithStmts<Box<Expr>>> {
let param_translation = self.convert_exprs(ctx, ids)?;
param_translation.and_then(|mut params| {
// 在静态环境中使用时，我们不能调用标准函数，因为它们不是 const，所以我们被迫进行转型
let call = if ctx.is_static {
let tuple = mk().tuple_expr(params);
transmute_expr(mk().infer_ty(), mk().infer_ty(), tuple)
} else {
let fn_call_name = match (&self.ast_context[ctype].kind, len) {
(Float, 4) => "_mm_setr_ps",
(Float, 8) => "_mm256_setr_ps",
(Double, 2) => "_mm_setr_pd",
(Double, 4) => "_mm256_setr_pd",
(LongLong, 2) => "_mm_set_epi64x",
(LongLong, 4) => "_mm256_setr_epi64x",
(Char, 8) => "_mm_setr_pi8",
(Char, 16) => "_mm_setr_epi8",
(Char, 32) => "_mm256_setr_epi8",
(Int, 2) => "_mm_setr_pi32",
(Int, 4) => "_mm_setr_epi32",
(Int, 8) => "_mm256_setr_epi32",
(Short, 4) => "_mm_setr_pi16",
(Short, 8) => "_mm_setr_epi16",
(Short, 16) => "_mm256_setr_epi16",
e => return Err(format_err!("未知的向量初始化列表: {:?}", e).into()),
};
self.import_simd_function(fn_call_name)?;
// rust 缺少对 _mm_setr_epi64x 的支持，因此我们必须对 _mm_set_epi64x 使用反向参数
if fn_call_name == "_mm_set_epi64x" {
params.reverse();
}
mk().call_expr(mk().ident_expr(fn_call_name), params)
};
if ctx.is_used() {
Ok(WithStmts::new_val(call))
} else {
Ok(WithStmts::new(
vec![mk().expr_stmt(call)],
self.panic_or_err("未使用的 shuffle vector 返回值没有值"),
))
}
})
}
pub fn convert_shuffle_vector(
&self,
ctx: ExprContext,
child_expr_ids: &[CExprId],
) -> TranslationResult<WithStmts<Box<Expr>>> {
//
}
fn strip_vector_explicit_cast(&self, expr_id: CExprId) -> (&CTypeKind, CExprId, usize) {
}
main_function.rs
这个模块是用于将C语言的main函数翻译为Rust的。
在该模块中，首先导入了所需的模块和库。
然后定义了一个名为Translation的结构体的实现（impl）。在这个实现中，定义了一个名为convert_main的方法，该方法用于将C语言的main函数转换为Rust的等价表示。
该方法接收一个参数，代表C语言main函数的ID，然后尝试提取其参数、类型等信息，进行相应的转换。
如果成功获取了main函数的信息，则将其转换为Rust中的函数，并生成对应的代码。代码生成过程包括构建函数声明、生成函数体以及处理main函数的参数和返回值。
具体地，代码考虑了main函数的三种形式：无参数、两个参数（argc、argv）以及三个参数（argc、argv和envp）。对于每种形式，都生成了相应的Rust代码。
如果main函数的返回值类型为void，则在Rust中将其视为返回0的函数。否则，会将main函数的返回值转换为i32类型，并通过std::process::exit函数返回。
如果在提取main函数信息的过程中发生错误，或者main函数不是函数类型（例如是一个变量或类型定义），则返回一个包含错误信息的结果。
总的来说，这个模块的目标是在尽可能保持原始语义的情况下，将C语言的main函数翻译为Rust。
use super::*;
use failure::format_err;
use proc_macro2::{TokenStream, TokenTree};
impl<'c> Translation<'c> {
pub fn convert_main(&self, main_id: CDeclId) -> TranslationResult<Box<Item>> {
if let CDeclKind::Function {
ref parameters,
typ,
..
} = self.ast_context.index(main_id).kind
{
let ret: CTypeKind = match self.ast_context.resolve_type(typ).kind {
CTypeKind::Function(ret, _, _, _, _) => {
self.ast_context.resolve_type(ret.ctype).kind.clone()
}
ref k => {
return Err(format_err!(
"Type of main function {:?} was not a function type, got {:?}",
main_id,
k
)
.into())
}
};
let main_fn_name = self
.renamer
.borrow()
.get(&main_id)
.expect("Could not find main function in renamer");
let decl = mk().fn_decl("main", vec![], None, ReturnType::Default);
let main_fn = mk().path_expr(vec![main_fn_name]);
let exit_fn = mk().abs_path_expr(vec!["std", "process", "exit"]);
let args_fn = mk().abs_path_expr(vec!["std", "env", "args"]);
let vars_fn = mk().abs_path_expr(vec!["std", "env", "vars"]);
let no_args: Vec<Box<Expr>> = vec![];
let mut stmts: Vec<Stmt> = vec![];
let mut main_args: Vec<Box<Expr>> = vec![];
let n = parameters.len();
if n >= 2 {
// `argv` and `argc`
stmts.push(mk().local_stmt(Box::new(mk().local(
mk().mutbl().ident_pat("args"),
Some(mk().path_ty(vec![mk().path_segment_with_args(
"Vec",
mk().angle_bracketed_args(vec![
mk().mutbl().ptr_ty(mk().path_ty(vec!["libc", "c_char"])),
]),
)])),
Some(mk().call_expr(mk().path_expr(vec!["Vec", "new"]), vec![])),
))));
stmts.push(mk().semi_stmt(mk().for_expr(
mk().ident_pat("arg"),
mk().call_expr(args_fn, vec![]),
mk().block(vec![mk().semi_stmt(mk().method_call_expr(
mk().path_expr(vec!["args"]),
"push",
vec![mk().method_call_expr(
mk().method_call_expr(
mk().call_expr(
// TODO(kkysen) change `"std"` to `"alloc"` after `#![feature(alloc_c_string)]` is stabilized in `1.63.0`
mk().abs_path_expr(vec!["std", "ffi", "CString", "new"]),
vec![mk().path_expr(vec!["arg"])],
),
"expect",
vec![mk().lit_expr("Failed to convert argument into CString.")],
),
"into_raw",
vec![],
)],
))]),
None::<Ident>,
)));
stmts.push(mk().semi_stmt(mk().method_call_expr(
mk().path_expr(vec!["args"]),
"push",
vec![
mk().call_expr(mk().abs_path_expr(vec!["core", "ptr", "null_mut"]), vec![]),
],
)));
let argc_ty: Box<Type> = match self.ast_context.index(parameters[0]).kind {
CDeclKind::Variable { ref typ, .. } => self.convert_type(typ.ctype),
_ => Err(TranslationError::generic(
"Cannot find type of 'argc' argument in main function",
)),
}?;
let argv_ty: Box<Type> = match self.ast_context.index(parameters[1]).kind {
CDeclKind::Variable { ref typ, .. } => self.convert_type(typ.ctype),
_ => Err(TranslationError::generic(
"Cannot find type of 'argv' argument in main function",
)),
}?;
let args = mk().ident_expr("args");
let argc = mk().binary_expr(
BinOp::Sub(Default::default()),
mk().method_call_expr(args.clone(), "len", no_args.clone()),
mk().lit_expr(mk().int_lit(1, "")),
);
let argv = mk().method_call_expr(args, "as_mut_ptr", no_args.clone());
main_args.push(mk().cast_expr(argc, argc_ty));
main_args.push(mk().cast_expr(argv, argv_ty));
}
if n >= 3 {
// non-standard `envp`
stmts.push(mk().local_stmt(Box::new(mk().local(
mk().mutbl().ident_pat("vars"),
Some(mk().path_ty(vec![mk().path_segment_with_args(
"Vec",
mk().angle_bracketed_args(vec![
mk().mutbl().ptr_ty(mk().path_ty(vec!["libc", "c_char"])),
]),
)])),
Some(mk().call_expr(mk().path_expr(vec!["Vec", "new"]), vec![])),
))));
let var_name_ident = mk().ident("var_name");
let var_value_ident = mk().ident("var_value");
stmts.push(mk().semi_stmt(mk().for_expr(
mk().tuple_pat(vec![
mk().ident_pat("var_name"),
mk().ident_pat("var_value"),
]),
mk().call_expr(vars_fn, vec![]),
mk().block(vec![
mk().local_stmt(Box::new(
mk().local(
mk().ident_pat("var"),
Some(mk().path_ty(vec!["String"])),
Some(
mk().mac_expr(
mk().mac(
mk().path(vec!["format"]),
vec![
TokenTree::Literal(
proc_macro2::Literal::string("{}={}"),
),
TokenTree::Punct(Punct::new(
',',
proc_macro2::Spacing::Alone,
)),
TokenTree::Ident(var_name_ident),
TokenTree::Punct(Punct::new(
',',
proc_macro2::Spacing::Alone,
)),
TokenTree::Ident(var_value_ident),
]
.into_iter()
.collect::<TokenStream>(),
MacroDelimiter::Paren(Default::default()),
),
),
),
),
)),
mk().semi_stmt(mk().method_call_expr(
mk().path_expr(vec!["vars"]),
"push",
vec![mk().method_call_expr(
mk().method_call_expr(
mk().call_expr(
mk().abs_path_expr(vec![
// TODO(kkysen) change `"std"` to `"alloc"` after `#![feature(alloc_c_string)]` is stabilized in `1.63.0`
"std", "ffi", "CString", "new",
]),
vec![mk().path_expr(vec!["var"])],
),
"expect",
vec![mk().lit_expr(
"Failed to convert environment variable into CString."
)],
),
"into_raw",
vec![],
)],
)),
]),
None as Option<Ident>,
)));
stmts.push(mk().semi_stmt(mk().method_call_expr(
mk().path_expr(vec!["vars"]),
"push",
vec![
mk().call_expr(mk().abs_path_expr(vec!["core", "ptr", "null_mut"]), vec![]),
],
)));
let envp_ty: Box<Type> = match self.ast_context.index(parameters[2]).kind {
CDeclKind::Variable { ref typ, .. } => self.convert_type(typ.ctype),
_ => Err(TranslationError::generic(
"Cannot find type of 'envp' argument in main function",
)),
}?;
let envp = mk().method_call_expr(mk().ident_expr("vars"), "as_mut_ptr", no_args);
main_args.push(mk().cast_expr(envp, envp_ty));
}
// Check `main` has the right form
if n != 0 && n != 2 && n != 3 {
return Err(format_err!(
"Main function should have 0, 2, or 3 parameters, not {}.",
n
)
.into());
};
if let CTypeKind::Void = ret {
let call_main = mk().call_expr(main_fn, main_args);
let unsafe_block = mk().unsafe_block(vec![mk().expr_stmt(call_main)]);
stmts.push(mk().expr_stmt(mk().unsafe_block_expr(unsafe_block)));
let exit_arg = mk().lit_expr(mk().int_lit(0, "i32"));
let call_exit = mk().call_expr(exit_fn, vec![exit_arg]);
stmts.push(mk().semi_stmt(call_exit));
} else {
let call_main = mk().cast_expr(
mk().call_expr(main_fn, main_args),
mk().path_ty(vec!["i32"]),
);
let call_exit = mk().call_expr(exit_fn, vec![call_main]);
let unsafe_block = mk().unsafe_block(vec![mk().expr_stmt(call_exit)]);
stmts.push(mk().expr_stmt(mk().unsafe_block_expr(unsafe_block)));
};
let block = mk().block(stmts);
Ok(mk().pub_().fn_item(decl, block))
} else {
Err(TranslationError::generic(
"Cannot translate non-function main entry point",
))
}
}
}
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