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Fix #570: Honor #![no_builtins] attribute by passing -fno-builtin to GCC #853

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Fix #570: Honor #![no_builtins] attribute by passing -fno-builtin to GCC #853

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12 changes: 11 additions & 1 deletion src/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ use std::sync::Arc;
use std::time::Instant;

use gccjit::{CType, Context, FunctionType, GlobalKind};
use rustc_ast::attr;
use rustc_codegen_ssa::ModuleCodegen;
use rustc_codegen_ssa::base::maybe_create_entry_wrapper;
use rustc_codegen_ssa::mono_item::MonoItemExt;
Expand All @@ -14,7 +15,7 @@ use rustc_middle::dep_graph;
use rustc_middle::mir::mono::Visibility;
use rustc_middle::ty::TyCtxt;
use rustc_session::config::DebugInfo;
use rustc_span::Symbol;
use rustc_span::{Symbol, sym};
#[cfg(feature = "master")]
use rustc_target::spec::SymbolVisibility;
use rustc_target::spec::{Arch, RelocModel};
Expand Down Expand Up @@ -136,6 +137,15 @@ pub fn compile_codegen_unit(
// NOTE: Rust relies on LLVM doing wrapping on overflow.
context.add_command_line_option("-fwrapv");

// NOTE: We need to honor the `#![no_builtins]` attribute to prevent GCC from
// replacing code patterns (like loops) with calls to builtins (like memset).
// This is important for crates like `compiler_builtins` that implement these functions.
// See https://github.com/rust-lang/rustc_codegen_gcc/issues/570
let crate_attrs = tcx.hir_attrs(rustc_hir::CRATE_HIR_ID);
if attr::contains_name(crate_attrs, sym::no_builtins) {
context.add_command_line_option("-fno-builtin");
}

if let Some(model) = tcx.sess.code_model() {
use rustc_target::spec::CodeModel;

Expand Down
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