1 files changed, 71 insertions, 0 deletions
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
new file mode 100644
index 00000000000..29edd66049c
--- /dev/null
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
@@ -0,0 +1,71 @@
+// .debug_gdb_scripts binary section.
+
+use crate::llvm;
+
+use crate::builder::Builder;
+use crate::common::CodegenCx;
+use crate::value::Value;
+use rustc_codegen_ssa::traits::*;
+use rustc_middle::bug;
+use rustc_session::config::DebugInfo;
+
+use rustc_span::symbol::sym;
+
+/// Inserts a side-effect free instruction sequence that makes sure that the
+/// .debug_gdb_scripts global is referenced, so it isn't removed by the linker.
+pub fn insert_reference_to_gdb_debug_scripts_section_global(bx: &mut Builder<'_, '_, '_>) {
+    if needs_gdb_debug_scripts_section(bx) {
+        let gdb_debug_scripts_section = get_or_insert_gdb_debug_scripts_section_global(bx);
+        // Load just the first byte as that's all that's necessary to force
+        // LLVM to keep around the reference to the global.
+        let indices = [bx.const_i32(0), bx.const_i32(0)];
+        let element = bx.inbounds_gep(gdb_debug_scripts_section, &indices);
+        let volative_load_instruction = bx.volatile_load(element);
+        unsafe {
+            llvm::LLVMSetAlignment(volative_load_instruction, 1);
+        }
+    }
+}
+
+/// Allocates the global variable responsible for the .debug_gdb_scripts binary
+/// section.
+pub fn get_or_insert_gdb_debug_scripts_section_global(cx: &CodegenCx<'ll, '_>) -> &'ll Value {
+    let c_section_var_name = "__rustc_debug_gdb_scripts_section__\0";
+    let section_var_name = &c_section_var_name[..c_section_var_name.len() - 1];
+
+    let section_var =
+        unsafe { llvm::LLVMGetNamedGlobal(cx.llmod, c_section_var_name.as_ptr().cast()) };
+
+    section_var.unwrap_or_else(|| {
+        let section_name = b".debug_gdb_scripts\0";
+        let section_contents = b"\x01gdb_load_rust_pretty_printers.py\0";
+
+        unsafe {
+            let llvm_type = cx.type_array(cx.type_i8(), section_contents.len() as u64);
+
+            let section_var = cx
+                .define_global(section_var_name, llvm_type)
+                .unwrap_or_else(|| bug!("symbol `{}` is already defined", section_var_name));
+            llvm::LLVMSetSection(section_var, section_name.as_ptr().cast());
+            llvm::LLVMSetInitializer(section_var, cx.const_bytes(section_contents));
+            llvm::LLVMSetGlobalConstant(section_var, llvm::True);
+            llvm::LLVMSetUnnamedAddress(section_var, llvm::UnnamedAddr::Global);
+            llvm::LLVMRustSetLinkage(section_var, llvm::Linkage::LinkOnceODRLinkage);
+            // This should make sure that the whole section is not larger than
+            // the string it contains. Otherwise we get a warning from GDB.
+            llvm::LLVMSetAlignment(section_var, 1);
+            section_var
+        }
+    })
+}
+
+pub fn needs_gdb_debug_scripts_section(cx: &CodegenCx<'_, '_>) -> bool {
+    let omit_gdb_pretty_printer_section = cx
+        .tcx
+        .sess
+        .contains_name(&cx.tcx.hir().krate_attrs(), sym::omit_gdb_pretty_printer_section);
+
+    !omit_gdb_pretty_printer_section
+        && cx.sess().opts.debuginfo != DebugInfo::None
+        && cx.sess().target.target.options.emit_debug_gdb_scripts
+}