Auto merge of #86844 - bjorn3:global_alloc_improvements, r=pnkfelix
Support #[global_allocator] without the allocator shim This makes it possible to use liballoc/libstd in combination with `--emit obj` if you use `#[global_allocator]`. This is what rust-for-linux uses right now and systemd may use in the future. Currently they have to depend on the exact implementation of the allocator shim to create one themself as `--emit obj` doesn't create an allocator shim. Note that currently the allocator shim also defines the oom error handler, which is normally required too. Once `#![feature(default_alloc_error_handler)]` becomes the only option, this can be avoided. In addition when using only fallible allocator methods and either `--cfg no_global_oom_handling` for liballoc (like rust-for-linux) or `--gc-sections` no references to the oom error handler will exist. To avoid this feature being insta-stable, you will have to define `__rust_no_alloc_shim_is_unstable` to avoid linker errors. (Labeling this with both T-compiler and T-lang as it originally involved both an implementation detail and had an insta-stable user facing change. As noted above, the `__rust_no_alloc_shim_is_unstable` symbol requirement should prevent unintended dependence on this unstable feature.)
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commit
a2b1646c59
19 changed files with 357 additions and 216 deletions
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@ -1,10 +1,12 @@
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use crate::attributes;
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use libc::c_uint;
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use rustc_ast::expand::allocator::{AllocatorKind, AllocatorTy, ALLOCATOR_METHODS};
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use rustc_ast::expand::allocator::{
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alloc_error_handler_name, default_fn_name, global_fn_name, AllocatorKind, AllocatorTy,
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ALLOCATOR_METHODS, NO_ALLOC_SHIM_IS_UNSTABLE,
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};
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use rustc_middle::bug;
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use rustc_middle::ty::TyCtxt;
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use rustc_session::config::{DebugInfo, OomStrategy};
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use rustc_span::symbol::sym;
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use crate::debuginfo;
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use crate::llvm::{self, False, True};
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@ -29,75 +31,78 @@ pub(crate) unsafe fn codegen(
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let i8p = llvm::LLVMPointerType(i8, 0);
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let void = llvm::LLVMVoidTypeInContext(llcx);
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for method in ALLOCATOR_METHODS {
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let mut args = Vec::with_capacity(method.inputs.len());
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for ty in method.inputs.iter() {
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match *ty {
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AllocatorTy::Layout => {
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args.push(usize); // size
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args.push(usize); // align
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if kind == AllocatorKind::Default {
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for method in ALLOCATOR_METHODS {
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let mut args = Vec::with_capacity(method.inputs.len());
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for ty in method.inputs.iter() {
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match *ty {
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AllocatorTy::Layout => {
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args.push(usize); // size
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args.push(usize); // align
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}
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AllocatorTy::Ptr => args.push(i8p),
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AllocatorTy::Usize => args.push(usize),
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AllocatorTy::ResultPtr | AllocatorTy::Unit => panic!("invalid allocator arg"),
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}
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AllocatorTy::Ptr => args.push(i8p),
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AllocatorTy::Usize => args.push(usize),
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AllocatorTy::ResultPtr | AllocatorTy::Unit => panic!("invalid allocator arg"),
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}
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}
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let output = match method.output {
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AllocatorTy::ResultPtr => Some(i8p),
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AllocatorTy::Unit => None,
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let output = match method.output {
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AllocatorTy::ResultPtr => Some(i8p),
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AllocatorTy::Unit => None,
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AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
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panic!("invalid allocator output")
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AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
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panic!("invalid allocator output")
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}
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};
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let ty = llvm::LLVMFunctionType(
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output.unwrap_or(void),
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args.as_ptr(),
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args.len() as c_uint,
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False,
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);
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let name = global_fn_name(method.name);
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let llfn =
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llvm::LLVMRustGetOrInsertFunction(llmod, name.as_ptr().cast(), name.len(), ty);
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if tcx.sess.target.default_hidden_visibility {
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llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
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}
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if tcx.sess.must_emit_unwind_tables() {
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let uwtable = attributes::uwtable_attr(llcx);
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attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
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}
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};
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let ty = llvm::LLVMFunctionType(
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output.unwrap_or(void),
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args.as_ptr(),
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args.len() as c_uint,
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False,
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);
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let name = format!("__rust_{}", method.name);
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let llfn = llvm::LLVMRustGetOrInsertFunction(llmod, name.as_ptr().cast(), name.len(), ty);
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if tcx.sess.target.default_hidden_visibility {
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llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
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let callee = default_fn_name(method.name);
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let callee =
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llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
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llvm::LLVMRustSetVisibility(callee, llvm::Visibility::Hidden);
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let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".as_ptr().cast());
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let llbuilder = llvm::LLVMCreateBuilderInContext(llcx);
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llvm::LLVMPositionBuilderAtEnd(llbuilder, llbb);
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let args = args
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.iter()
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.enumerate()
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.map(|(i, _)| llvm::LLVMGetParam(llfn, i as c_uint))
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.collect::<Vec<_>>();
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let ret = llvm::LLVMRustBuildCall(
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llbuilder,
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ty,
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callee,
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args.as_ptr(),
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args.len() as c_uint,
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[].as_ptr(),
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0 as c_uint,
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);
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llvm::LLVMSetTailCall(ret, True);
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if output.is_some() {
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llvm::LLVMBuildRet(llbuilder, ret);
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} else {
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llvm::LLVMBuildRetVoid(llbuilder);
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}
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llvm::LLVMDisposeBuilder(llbuilder);
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}
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if tcx.sess.must_emit_unwind_tables() {
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let uwtable = attributes::uwtable_attr(llcx);
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attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
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}
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let callee = kind.fn_name(method.name);
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let callee =
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llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
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llvm::LLVMRustSetVisibility(callee, llvm::Visibility::Hidden);
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let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".as_ptr().cast());
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let llbuilder = llvm::LLVMCreateBuilderInContext(llcx);
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llvm::LLVMPositionBuilderAtEnd(llbuilder, llbb);
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let args = args
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.iter()
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.enumerate()
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.map(|(i, _)| llvm::LLVMGetParam(llfn, i as c_uint))
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.collect::<Vec<_>>();
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let ret = llvm::LLVMRustBuildCall(
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llbuilder,
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ty,
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callee,
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args.as_ptr(),
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args.len() as c_uint,
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[].as_ptr(),
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0 as c_uint,
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);
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llvm::LLVMSetTailCall(ret, True);
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if output.is_some() {
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llvm::LLVMBuildRet(llbuilder, ret);
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} else {
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llvm::LLVMBuildRetVoid(llbuilder);
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}
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llvm::LLVMDisposeBuilder(llbuilder);
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}
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// rust alloc error handler
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@ -118,7 +123,7 @@ pub(crate) unsafe fn codegen(
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attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
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}
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let callee = alloc_error_handler_kind.fn_name(sym::oom);
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let callee = alloc_error_handler_name(alloc_error_handler_kind);
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let callee = llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
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// -> ! DIFlagNoReturn
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attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);
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@ -156,6 +161,14 @@ pub(crate) unsafe fn codegen(
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let llval = llvm::LLVMConstInt(i8, val as u64, False);
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llvm::LLVMSetInitializer(ll_g, llval);
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let name = NO_ALLOC_SHIM_IS_UNSTABLE;
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let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_ptr().cast(), name.len(), i8);
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if tcx.sess.target.default_hidden_visibility {
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llvm::LLVMRustSetVisibility(ll_g, llvm::Visibility::Hidden);
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}
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let llval = llvm::LLVMConstInt(i8, 0, False);
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llvm::LLVMSetInitializer(ll_g, llval);
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if tcx.sess.opts.debuginfo != DebugInfo::None {
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let dbg_cx = debuginfo::CodegenUnitDebugContext::new(llmod);
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debuginfo::metadata::build_compile_unit_di_node(tcx, module_name, &dbg_cx);
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