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Don't use an allocator shim for #[global_allocator]

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This makes it possible to use liballoc/libstd in combination with
`--emit obj` if you use `#[global_allocator]`. Making it work for the
default libstd allocator would require weak functions, which are not
well supported on all systems.
This commit is contained in:
bjorn3 2021-07-03 16:46:41 +02:00 • committed by bjorn3
parent 79fa6ce7a1
commit 4ce20663f7
4 changed files with 176 additions and 159 deletions
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136
compiler/rustc_codegen_llvm/src/allocator.rs
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@ -1,10 +1,11 @@
use crate::attributes;
use libc::c_uint;
use rustc_ast::expand::allocator::{AllocatorKind, AllocatorTy, ALLOCATOR_METHODS};
use rustc_ast::expand::allocator::{
alloc_error_handler_name, AllocatorKind, AllocatorTy, ALLOCATOR_METHODS,
};
use rustc_middle::bug;
use rustc_middle::ty::TyCtxt;
use rustc_session::config::{DebugInfo, OomStrategy};
use rustc_span::symbol::sym;
use crate::debuginfo;
use crate::llvm::{self, False, True};
@ -29,75 +30,78 @@ pub(crate) unsafe fn codegen(
let i8p = llvm::LLVMPointerType(i8, 0);
let void = llvm::LLVMVoidTypeInContext(llcx);
for method in ALLOCATOR_METHODS {
let mut args = Vec::with_capacity(method.inputs.len());
for ty in method.inputs.iter() {
match *ty {
AllocatorTy::Layout => {
args.push(usize); // size
args.push(usize); // align
if kind == AllocatorKind::Default {
for method in ALLOCATOR_METHODS {
let mut args = Vec::with_capacity(method.inputs.len());
for ty in method.inputs.iter() {
match *ty {
AllocatorTy::Layout => {
args.push(usize); // size
args.push(usize); // align
}
AllocatorTy::Ptr => args.push(i8p),
AllocatorTy::Usize => args.push(usize),
AllocatorTy::ResultPtr | AllocatorTy::Unit => panic!("invalid allocator arg"),
}
AllocatorTy::Ptr => args.push(i8p),
AllocatorTy::Usize => args.push(usize),
AllocatorTy::ResultPtr | AllocatorTy::Unit => panic!("invalid allocator arg"),
}
}
let output = match method.output {
AllocatorTy::ResultPtr => Some(i8p),
AllocatorTy::Unit => None,
let output = match method.output {
AllocatorTy::ResultPtr => Some(i8p),
AllocatorTy::Unit => None,
AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
panic!("invalid allocator output")
AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
panic!("invalid allocator output")
}
};
let ty = llvm::LLVMFunctionType(
output.unwrap_or(void),
args.as_ptr(),
args.len() as c_uint,
False,
);
let name = format!("__rust_{}", method.name);
let llfn =
llvm::LLVMRustGetOrInsertFunction(llmod, name.as_ptr().cast(), name.len(), ty);
if tcx.sess.target.default_hidden_visibility {
llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
}
if tcx.sess.must_emit_unwind_tables() {
let uwtable = attributes::uwtable_attr(llcx);
attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
}
};
let ty = llvm::LLVMFunctionType(
output.unwrap_or(void),
args.as_ptr(),
args.len() as c_uint,
False,
);
let name = format!("__rust_{}", method.name);
let llfn = llvm::LLVMRustGetOrInsertFunction(llmod, name.as_ptr().cast(), name.len(), ty);
if tcx.sess.target.default_hidden_visibility {
llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
let callee = AllocatorKind::Default.fn_name(method.name);
let callee =
llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
llvm::LLVMRustSetVisibility(callee, llvm::Visibility::Hidden);
let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".as_ptr().cast());
let llbuilder = llvm::LLVMCreateBuilderInContext(llcx);
llvm::LLVMPositionBuilderAtEnd(llbuilder, llbb);
let args = args
.iter()
.enumerate()
.map(|(i, _)| llvm::LLVMGetParam(llfn, i as c_uint))
.collect::<Vec<_>>();
let ret = llvm::LLVMRustBuildCall(
llbuilder,
ty,
callee,
args.as_ptr(),
args.len() as c_uint,
[].as_ptr(),
0 as c_uint,
);
llvm::LLVMSetTailCall(ret, True);
if output.is_some() {
llvm::LLVMBuildRet(llbuilder, ret);
} else {
llvm::LLVMBuildRetVoid(llbuilder);
}
llvm::LLVMDisposeBuilder(llbuilder);
}
if tcx.sess.must_emit_unwind_tables() {
let uwtable = attributes::uwtable_attr(llcx);
attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
}
let callee = kind.fn_name(method.name);
let callee =
llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
llvm::LLVMRustSetVisibility(callee, llvm::Visibility::Hidden);
let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".as_ptr().cast());
let llbuilder = llvm::LLVMCreateBuilderInContext(llcx);
llvm::LLVMPositionBuilderAtEnd(llbuilder, llbb);
let args = args
.iter()
.enumerate()
.map(|(i, _)| llvm::LLVMGetParam(llfn, i as c_uint))
.collect::<Vec<_>>();
let ret = llvm::LLVMRustBuildCall(
llbuilder,
ty,
callee,
args.as_ptr(),
args.len() as c_uint,
[].as_ptr(),
0 as c_uint,
);
llvm::LLVMSetTailCall(ret, True);
if output.is_some() {
llvm::LLVMBuildRet(llbuilder, ret);
} else {
llvm::LLVMBuildRetVoid(llbuilder);
}
llvm::LLVMDisposeBuilder(llbuilder);
}
// rust alloc error handler
@ -118,7 +122,7 @@ pub(crate) unsafe fn codegen(
attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
}
let callee = alloc_error_handler_kind.fn_name(sym::oom);
let callee = alloc_error_handler_name(alloc_error_handler_kind);
let callee = llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
// -> ! DIFlagNoReturn
attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);