rust-lang/rust
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

Auto merge of #140914 - Zalathar:asm-bindings, r=compiler-errors

Browse Source 
cg_llvm: Clean up some inline assembly bindings

This PR combines a few loosely-related cleanups to LLVM bindings related to inline assembly. These include:
- Replacing `LLVMRustInlineAsm` with LLVM-C's `LLVMGetInlineAsm`
- Adjusting FFI declarations to avoid the need for explicit `as_c_char_ptr` conversions
- Flattening control flow in `inline_asm_call`

There should be no functional changes.
This commit is contained in:
bors
2025-05-12 17:39:21 +00:00
parent 420ca7104f eccf0647d3
commit 1a7f290a9a
5 changed files with 93 additions and 113 deletions
Download Patch File Download Diff File Expand all files Collapse all files

126
compiler/rustc_codegen_llvm/src/asm.rs
View File

@@ -14,7 +14,7 @@ use smallvec::SmallVec;
use tracing::debug;
use crate::builder::Builder;
use crate::common::{AsCCharPtr, Funclet};
use crate::common::Funclet;
use crate::context::CodegenCx;
use crate::type_::Type;
use crate::type_of::LayoutLlvmExt;
@@ -435,13 +435,7 @@ impl<'tcx> AsmCodegenMethods<'tcx> for CodegenCx<'_, 'tcx> {
template_str.push_str("\n.att_syntax\n");
}
unsafe {
llvm::LLVMAppendModuleInlineAsm(
self.llmod,
template_str.as_c_char_ptr(),
template_str.len(),
);
}
llvm::append_module_inline_asm(self.llmod, template_str.as_bytes());
}
fn mangled_name(&self, instance: Instance<'tcx>) -> String {
@@ -482,67 +476,67 @@ pub(crate) fn inline_asm_call<'ll>(
debug!("Asm Output Type: {:?}", output);
let fty = bx.cx.type_func(&argtys, output);
// Ask LLVM to verify that the constraints are well-formed.
let constraints_ok =
unsafe { llvm::LLVMRustInlineAsmVerify(fty, cons.as_c_char_ptr(), cons.len()) };
let constraints_ok = unsafe { llvm::LLVMRustInlineAsmVerify(fty, cons.as_ptr(), cons.len()) };
debug!("constraint verification result: {:?}", constraints_ok);
if constraints_ok {
let v = unsafe {
llvm::LLVMRustInlineAsm(
fty,
asm.as_c_char_ptr(),
asm.len(),
cons.as_c_char_ptr(),
cons.len(),
volatile,
alignstack,
dia,
can_throw,
)
};
let call = if !labels.is_empty() {
assert!(catch_funclet.is_none());
bx.callbr(fty, None, None, v, inputs, dest.unwrap(), labels, None, None)
} else if let Some((catch, funclet)) = catch_funclet {
bx.invoke(fty, None, None, v, inputs, dest.unwrap(), catch, funclet, None)
} else {
bx.call(fty, None, None, v, inputs, None, None)
};
// Store mark in a metadata node so we can map LLVM errors
// back to source locations. See #17552.
let key = "srcloc";
let kind = bx.get_md_kind_id(key);
// `srcloc` contains one 64-bit integer for each line of assembly code,
// where the lower 32 bits hold the lo byte position and the upper 32 bits
// hold the hi byte position.
let mut srcloc = vec![];
if dia == llvm::AsmDialect::Intel && line_spans.len() > 1 {
// LLVM inserts an extra line to add the ".intel_syntax", so add
// a dummy srcloc entry for it.
//
// Don't do this if we only have 1 line span since that may be
// due to the asm template string coming from a macro. LLVM will
// default to the first srcloc for lines that don't have an
// associated srcloc.
srcloc.push(llvm::LLVMValueAsMetadata(bx.const_u64(0)));
}
srcloc.extend(line_spans.iter().map(|span| {
llvm::LLVMValueAsMetadata(
bx.const_u64(u64::from(span.lo().to_u32()) | (u64::from(span.hi().to_u32()) << 32)),
)
}));
let md = unsafe { llvm::LLVMMDNodeInContext2(bx.llcx, srcloc.as_ptr(), srcloc.len()) };
let md = bx.get_metadata_value(md);
llvm::LLVMSetMetadata(call, kind, md);
Some(call)
} else {
// LLVM has detected an issue with our constraints, bail out
None
if !constraints_ok {
// LLVM has detected an issue with our constraints, so bail out.
return None;
}
let v = unsafe {
llvm::LLVMGetInlineAsm(
fty,
asm.as_ptr(),
asm.len(),
cons.as_ptr(),
cons.len(),
volatile,
alignstack,
dia,
can_throw,
)
};
let call = if !labels.is_empty() {
assert!(catch_funclet.is_none());
bx.callbr(fty, None, None, v, inputs, dest.unwrap(), labels, None, None)
} else if let Some((catch, funclet)) = catch_funclet {
bx.invoke(fty, None, None, v, inputs, dest.unwrap(), catch, funclet, None)
} else {
bx.call(fty, None, None, v, inputs, None, None)
};
// Store mark in a metadata node so we can map LLVM errors
// back to source locations. See #17552.
let key = "srcloc";
let kind = bx.get_md_kind_id(key);
// `srcloc` contains one 64-bit integer for each line of assembly code,
// where the lower 32 bits hold the lo byte position and the upper 32 bits
// hold the hi byte position.
let mut srcloc = vec![];
if dia == llvm::AsmDialect::Intel && line_spans.len() > 1 {
// LLVM inserts an extra line to add the ".intel_syntax", so add
// a dummy srcloc entry for it.
//
// Don't do this if we only have 1 line span since that may be
// due to the asm template string coming from a macro. LLVM will
// default to the first srcloc for lines that don't have an
// associated srcloc.
srcloc.push(llvm::LLVMValueAsMetadata(bx.const_u64(0)));
}
srcloc.extend(line_spans.iter().map(|span| {
llvm::LLVMValueAsMetadata(
bx.const_u64(u64::from(span.lo().to_u32()) | (u64::from(span.hi().to_u32()) << 32)),
)
}));
let md = unsafe { llvm::LLVMMDNodeInContext2(bx.llcx, srcloc.as_ptr(), srcloc.len()) };
let md = bx.get_metadata_value(md);
llvm::LLVMSetMetadata(call, kind, md);
Some(call)
}
/// If the register is an xmm/ymm/zmm register then return its index.

4
compiler/rustc_codegen_llvm/src/back/write.rs
View File

@@ -1148,9 +1148,9 @@ unsafe fn embed_bitcode(
// We need custom section flags, so emit module-level inline assembly.
let section_flags = if cgcx.is_pe_coff { "n" } else { "e" };
let asm = create_section_with_flags_asm(".llvmbc", section_flags, bitcode);
llvm::LLVMAppendModuleInlineAsm(llmod, asm.as_c_char_ptr(), asm.len());
llvm::append_module_inline_asm(llmod, &asm);
let asm = create_section_with_flags_asm(".llvmcmd", section_flags, cmdline.as_bytes());
llvm::LLVMAppendModuleInlineAsm(llmod, asm.as_c_char_ptr(), asm.len());
llvm::append_module_inline_asm(llmod, &asm);
}
}
}

41
compiler/rustc_codegen_llvm/src/llvm/ffi.rs
View File

@@ -1,7 +1,7 @@
//! Bindings to the LLVM-C API (`LLVM*`), and to our own `extern "C"` wrapper
//! functions around the unstable LLVM C++ API (`LLVMRust*`).
//!
//! ## Passing pointer/length strings as `*const c_uchar`
//! ## Passing pointer/length strings as `*const c_uchar` (PTR_LEN_STR)
//!
//! Normally it's a good idea for Rust-side bindings to match the corresponding
//! C-side function declarations as closely as possible. But when passing `&str`
@@ -471,7 +471,7 @@ pub(crate) enum MetadataType {
MD_kcfi_type = 36,
}
/// LLVMRustAsmDialect
/// Must match the layout of `LLVMInlineAsmDialect`.
#[derive(Copy, Clone, PartialEq)]
#[repr(C)]
pub(crate) enum AsmDialect {
@@ -1014,8 +1014,25 @@ unsafe extern "C" {
pub(crate) fn LLVMGetDataLayoutStr(M: &Module) -> *const c_char;
pub(crate) fn LLVMSetDataLayout(M: &Module, Triple: *const c_char);
/// See Module::setModuleInlineAsm.
pub(crate) fn LLVMAppendModuleInlineAsm(M: &Module, Asm: *const c_char, Len: size_t);
/// Append inline assembly to a module. See `Module::appendModuleInlineAsm`.
pub(crate) fn LLVMAppendModuleInlineAsm(
M: &Module,
Asm: *const c_uchar, // See "PTR_LEN_STR".
Len: size_t,
);
/// Create the specified uniqued inline asm string. See `InlineAsm::get()`.
pub(crate) fn LLVMGetInlineAsm<'ll>(
Ty: &'ll Type,
AsmString: *const c_uchar, // See "PTR_LEN_STR".
AsmStringSize: size_t,
Constraints: *const c_uchar, // See "PTR_LEN_STR".
ConstraintsSize: size_t,
HasSideEffects: llvm::Bool,
IsAlignStack: llvm::Bool,
Dialect: AsmDialect,
CanThrow: llvm::Bool,
) -> &'ll Value;
// Operations on integer types
pub(crate) fn LLVMInt1TypeInContext(C: &Context) -> &Type;
@@ -1766,7 +1783,7 @@ unsafe extern "C" {
pub(crate) fn LLVMDIBuilderCreateNameSpace<'ll>(
Builder: &DIBuilder<'ll>,
ParentScope: Option<&'ll Metadata>,
Name: *const c_uchar,
Name: *const c_uchar, // See "PTR_LEN_STR".
NameLen: size_t,
ExportSymbols: llvm::Bool,
) -> &'ll Metadata;
@@ -1994,21 +2011,9 @@ unsafe extern "C" {
/// Prints the statistics collected by `-Zprint-codegen-stats`.
pub(crate) fn LLVMRustPrintStatistics(OutStr: &RustString);
/// Prepares inline assembly.
pub(crate) fn LLVMRustInlineAsm(
Ty: &Type,
AsmString: *const c_char,
AsmStringLen: size_t,
Constraints: *const c_char,
ConstraintsLen: size_t,
SideEffects: Bool,
AlignStack: Bool,
Dialect: AsmDialect,
CanThrow: Bool,
) -> &Value;
pub(crate) fn LLVMRustInlineAsmVerify(
Ty: &Type,
Constraints: *const c_char,
Constraints: *const c_uchar, // See "PTR_LEN_STR".
ConstraintsLen: size_t,
) -> bool;

8
compiler/rustc_codegen_llvm/src/llvm/mod.rs
View File

@@ -441,3 +441,11 @@ pub(crate) fn set_dso_local<'ll>(v: &'ll Value) {
LLVMRustSetDSOLocal(v, true);
}
}
/// Safe wrapper for `LLVMAppendModuleInlineAsm`, which delegates to
/// `Module::appendModuleInlineAsm`.
pub(crate) fn append_module_inline_asm<'ll>(llmod: &'ll Module, asm: &[u8]) {
unsafe {
LLVMAppendModuleInlineAsm(llmod, asm.as_ptr(), asm.len());
}
}