Auto merge of #83592 - nagisa:nagisa/dso_local, r=davidtwco

Set dso_local for hidden, private and local items

This should probably have no real effect in most cases, as e.g. `hidden`
visibility already implies `dso_local` (or at least LLVM IR does not
preserve the `dso_local` setting if the item is already `hidden`), but
it should fix `-Crelocation-model=static` and improve codegen in
executables.

Note that this PR does not exhaustively port the logic in [clang], only the
portion that is necessary to fix a regression from LLVM 12 that relates to
`-Crelocation_model=static`.

Fixes #83335

[clang]: https://github.com/llvm/llvm-project/blob/3001d080c813da20b329303bf8f45451480e5905/clang/lib/CodeGen/CodeGenModule.cpp#L945-L1039

Author: bors

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -254,6 +254,7 @@ pub fn from_fn_attrs(cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value, instance: ty::
         attributes::emit_uwtable(llfn, true);
     }
 
+    // FIXME: none of these three functions interact with source level attributes.
     set_frame_pointer_elimination(cx, llfn);
     set_instrument_function(cx, llfn);
     set_probestack(cx, llfn);

compiler/rustc_codegen_llvm/src/callee.rs

@@ -14,6 +14,7 @@ use tracing::debug;
 
 use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt};
 use rustc_middle::ty::{self, Instance, TypeFoldable};
+use rustc_target::spec::RelocModel;
 
 /// Codegens a reference to a fn/method item, monomorphizing and
 /// inlining as it goes.
@@ -170,17 +171,19 @@ pub fn get_fn(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) -> &'ll Value
                     }
                 }
             }
-        }
 
-        // MinGW: For backward compatibility we rely on the linker to decide whether it
-        // should use dllimport for functions.
-        if cx.use_dll_storage_attrs
-            && tcx.is_dllimport_foreign_item(instance_def_id)
-            && tcx.sess.target.env != "gnu"
-        {
-            unsafe {
+            // MinGW: For backward compatibility we rely on the linker to decide whether it
+            // should use dllimport for functions.
+            if cx.use_dll_storage_attrs
+                && tcx.is_dllimport_foreign_item(instance_def_id)
+                && tcx.sess.target.env != "gnu"
+            {
                 llvm::LLVMSetDLLStorageClass(llfn, llvm::DLLStorageClass::DllImport);
             }
+
+            if cx.tcx.sess.relocation_model() == RelocModel::Static {
+                llvm::LLVMRustSetDSOLocal(llfn, true);
+            }
         }
 
         llfn

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1013,6 +1013,7 @@ extern "C" {
     pub fn LLVMSetSection(Global: &Value, Section: *const c_char);
     pub fn LLVMRustGetVisibility(Global: &Value) -> Visibility;
     pub fn LLVMRustSetVisibility(Global: &Value, Viz: Visibility);
+    pub fn LLVMRustSetDSOLocal(Global: &Value, is_dso_local: bool);
     pub fn LLVMGetAlignment(Global: &Value) -> c_uint;
     pub fn LLVMSetAlignment(Global: &Value, Bytes: c_uint);
     pub fn LLVMSetDLLStorageClass(V: &Value, C: DLLStorageClass);

compiler/rustc_codegen_llvm/src/mono_item.rs

@@ -10,7 +10,9 @@ pub use rustc_middle::mir::mono::MonoItem;
 use rustc_middle::mir::mono::{Linkage, Visibility};
 use rustc_middle::ty::layout::FnAbiExt;
 use rustc_middle::ty::{self, Instance, TypeFoldable};
+use rustc_session::config::CrateType;
 use rustc_target::abi::LayoutOf;
+use rustc_target::spec::RelocModel;
 use tracing::debug;
 
 impl PreDefineMethods<'tcx> for CodegenCx<'ll, 'tcx> {
@@ -35,6 +37,9 @@ impl PreDefineMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         unsafe {
             llvm::LLVMRustSetLinkage(g, base::linkage_to_llvm(linkage));
             llvm::LLVMRustSetVisibility(g, base::visibility_to_llvm(visibility));
+            if self.should_assume_dso_local(linkage, visibility) {
+                llvm::LLVMRustSetDSOLocal(g, true);
+            }
         }
 
         self.instances.borrow_mut().insert(instance, g);
@@ -79,6 +84,42 @@ impl PreDefineMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 
         attributes::from_fn_attrs(self, lldecl, instance);
 
+        unsafe {
+            if self.should_assume_dso_local(linkage, visibility) {
+                llvm::LLVMRustSetDSOLocal(lldecl, true);
+            }
+        }
+
         self.instances.borrow_mut().insert(instance, lldecl);
     }
 }
+
+impl CodegenCx<'ll, 'tcx> {
+    /// Whether a definition (NB: not declaration!) can be assumed to be local to a group of
+    /// libraries that form a single DSO or executable.
+    pub(crate) unsafe fn should_assume_dso_local(
+        &self,
+        linkage: Linkage,
+        visibility: Visibility,
+    ) -> bool {
+        if matches!(linkage, Linkage::Internal | Linkage::Private) {
+            return true;
+        }
+
+        if visibility != Visibility::Default && linkage != Linkage::ExternalWeak {
+            return true;
+        }
+
+        // Static relocation model should force copy relocations everywhere.
+        if self.tcx.sess.relocation_model() == RelocModel::Static {
+            return true;
+        }
+
+        // Symbols from executables can't really be imported any further.
+        if self.tcx.sess.crate_types().iter().all(|ty| *ty == CrateType::Executable) {
+            return true;
+        }
+
+        return false;
+    }
+}

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -1636,6 +1636,10 @@ extern "C" void LLVMRustSetVisibility(LLVMValueRef V,
   LLVMSetVisibility(V, fromRust(RustVisibility));
 }
 
+extern "C" void LLVMRustSetDSOLocal(LLVMValueRef Global, bool is_dso_local) {
+  unwrap<GlobalValue>(Global)->setDSOLocal(is_dso_local);
+}
+
 struct LLVMRustModuleBuffer {
   std::string data;
 };

src/test/assembly/static-relocation-model.rs

@@ -0,0 +1,44 @@
+// min-llvm-version: 12.0.0
+// needs-llvm-components: aarch64 x86
+// revisions:X64 A64
+// assembly-output: emit-asm
+// [X64] compile-flags: --target x86_64-unknown-linux-gnu -Crelocation-model=static
+// [A64] compile-flags: --target aarch64-unknown-linux-gnu -Crelocation-model=static
+
+#![feature(no_core, lang_items)]
+#![no_core]
+#![crate_type="rlib"]
+
+#[lang="sized"]
+trait Sized {}
+
+#[lang="copy"]
+trait Copy {}
+
+impl Copy for u8 {}
+
+extern "C" {
+    fn chaenomeles();
+}
+
+// CHECK-LABEL: banana:
+// x64: movb    chaenomeles, %{{[a,z]+}}
+// A64:      adrp    [[REG:[a-z0-9]+]], chaenomeles
+// A64-NEXT: ldrb    {{[a-z0-9]+}}, {{\[}}[[REG]], :lo12:chaenomeles]
+#[no_mangle]
+pub fn banana() -> u8 {
+    unsafe {
+        *(chaenomeles as *mut u8)
+    }
+}
+
+// CHECK-LABEL: peach:
+// x64: movb    banana, %{{[a,z]+}}
+// A64:      adrp    [[REG2:[a-z0-9]+]], banana
+// A64-NEXT: ldrb    {{[a-z0-9]+}}, {{\[}}[[REG2]], :lo12:banana]
+#[no_mangle]
+pub fn peach() -> u8 {
+    unsafe {
+        *(banana as *mut u8)
+    }
+}

src/test/codegen/abi-efiapi.rs

@@ -23,8 +23,8 @@ trait Copy { }
 
 //x86_64: define win64cc void @has_efiapi
 //i686: define void @has_efiapi
-//aarch64: define void @has_efiapi
-//arm: define void @has_efiapi
-//riscv: define void @has_efiapi
+//aarch64: define dso_local void @has_efiapi
+//arm: define dso_local void @has_efiapi
+//riscv: define dso_local void @has_efiapi
 #[no_mangle]
 pub extern "efiapi" fn has_efiapi() {}

src/test/codegen/abi-repr-ext.rs

@@ -6,7 +6,7 @@ pub enum Type {
     Type2 = 1
 }
 
-// CHECK: define signext i8 @test()
+// CHECK: define{{( dso_local)?}} signext i8 @test()
 #[no_mangle]
 pub extern "C" fn test() -> Type {
     Type::Type1

src/test/codegen/abi-sysv64.rs

@@ -1,17 +1,21 @@
 // Checks if the correct annotation for the sysv64 ABI is passed to
 // llvm. Also checks that the abi-sysv64 feature gate allows usage
 // of the sysv64 abi.
-
-// ignore-arm
-// ignore-aarch64
-// ignore-riscv64 sysv64 not supported
-
-// compile-flags: -C no-prepopulate-passes
+//
+// needs-llvm-components: x86
+// compile-flags: -C no-prepopulate-passes --target=x86_64-unknown-linux-gnu
 
 #![crate_type = "lib"]
+#![no_core]
+#![feature(abi_x86_interrupt, no_core, lang_items)]
+
+#[lang = "sized"]
+trait Sized {}
+#[lang = "copy"]
+trait Copy {}
 
 // CHECK: define x86_64_sysvcc i64 @has_sysv64_abi
 #[no_mangle]
 pub extern "sysv64" fn has_sysv64_abi(a: i64) -> i64 {
-    a * 2
+    a
 }

src/test/codegen/abi-x86-interrupt.rs

@@ -2,17 +2,20 @@
 // llvm. Also checks that the abi_x86_interrupt feature gate allows usage
 // of the x86-interrupt abi.
 
-// ignore-arm
-// ignore-aarch64
-// ignore-riscv64 x86-interrupt is not supported
-
-// compile-flags: -C no-prepopulate-passes
+// needs-llvm-components: x86
+// compile-flags: -C no-prepopulate-passes --target=x86_64-unknown-linux-gnu
 
 #![crate_type = "lib"]
-#![feature(abi_x86_interrupt)]
+#![no_core]
+#![feature(abi_x86_interrupt, no_core, lang_items)]
+
+#[lang = "sized"]
+trait Sized {}
+#[lang = "copy"]
+trait Copy {}
 
 // CHECK: define x86_intrcc i64 @has_x86_interrupt_abi
 #[no_mangle]
 pub extern "x86-interrupt" fn has_x86_interrupt_abi(a: i64) -> i64 {
-    a * 2
+    a
 }

src/test/codegen/cdylib-external-inline-fns.rs

@@ -2,42 +2,42 @@
 
 #![crate_type = "cdylib"]
 
-// CHECK: define void @a()
+// CHECK: define{{( dso_local)?}} void @a()
 #[no_mangle]
 #[inline]
 pub extern "C" fn a() {}
 
-// CHECK: define void @b()
+// CHECK: define{{( dso_local)?}} void @b()
 #[export_name = "b"]
 #[inline]
 pub extern "C" fn b() {}
 
-// CHECK: define void @c()
+// CHECK: define{{( dso_local)?}} void @c()
 #[no_mangle]
 #[inline]
 extern "C" fn c() {}
 
-// CHECK: define void @d()
+// CHECK: define{{( dso_local)?}} void @d()
 #[export_name = "d"]
 #[inline]
 extern "C" fn d() {}
 
-// CHECK: define void @e()
+// CHECK: define{{( dso_local)?}} void @e()
 #[no_mangle]
 #[inline(always)]
 pub extern "C" fn e() {}
 
-// CHECK: define void @f()
+// CHECK: define{{( dso_local)?}} void @f()
 #[export_name = "f"]
 #[inline(always)]
 pub extern "C" fn f() {}
 
-// CHECK: define void @g()
+// CHECK: define{{( dso_local)?}} void @g()
 #[no_mangle]
 #[inline(always)]
 extern "C" fn g() {}
 
-// CHECK: define void @h()
+// CHECK: define{{( dso_local)?}} void @h()
 #[export_name = "h"]
 #[inline(always)]
 extern "C" fn h() {}

src/test/codegen/dealloc-no-unwind.rs

@@ -1,4 +1,3 @@
-//
 // no-system-llvm
 // compile-flags: -O
 
@@ -15,7 +14,7 @@ impl Drop for A {
 
 #[no_mangle]
 pub fn a(a: Box<i32>) {
-    // CHECK-LABEL: define void @a
+    // CHECK-LABEL: define{{.*}}void @a
     // CHECK: call void @__rust_dealloc
     // CHECK-NEXT: call void @foo
     let _a = A;

src/test/codegen/external-no-mangle-fns.rs

@@ -4,30 +4,30 @@
 #![crate_type = "lib"]
 #![no_std]
 
-// CHECK: define void @a()
+// CHECK: define{{( dso_local)?}} void @a()
 #[no_mangle]
 fn a() {}
 
-// CHECK: define void @b()
+// CHECK: define{{( dso_local)?}} void @b()
 #[no_mangle]
 pub fn b() {}
 
 mod private {
-    // CHECK: define void @c()
+    // CHECK: define{{( dso_local)?}} void @c()
     #[no_mangle]
     fn c() {}
 
-    // CHECK: define void @d()
+    // CHECK: define{{( dso_local)?}} void @d()
     #[no_mangle]
     pub fn d() {}
 }
 
 const HIDDEN: () = {
-    // CHECK: define void @e()
+    // CHECK: define{{( dso_local)?}} void @e()
     #[no_mangle]
     fn e() {}
 
-    // CHECK: define void @f()
+    // CHECK: define{{( dso_local)?}} void @f()
     #[no_mangle]
     pub fn f() {}
 };
@@ -38,13 +38,13 @@ const HIDDEN: () = {
 // CHECK-NEXT: define internal
 #[inline(never)]
 fn x() {
-    // CHECK: define void @g()
+    // CHECK: define{{( dso_local)?}} void @g()
     #[no_mangle]
     fn g() {
         x();
     }
 
-    // CHECK: define void @h()
+    // CHECK: define{{( dso_local)?}} void @h()
     #[no_mangle]
     pub fn h() {}
 
@@ -54,22 +54,22 @@ fn x() {
     }
 }
 
-// CHECK: define void @i()
+// CHECK: define{{( dso_local)?}} void @i()
 #[no_mangle]
 #[inline]
 fn i() {}
 
-// CHECK: define void @j()
+// CHECK: define{{( dso_local)?}} void @j()
 #[no_mangle]
 #[inline]
 pub fn j() {}
 
-// CHECK: define void @k()
+// CHECK: define{{( dso_local)?}} void @k()
 #[no_mangle]
 #[inline(always)]
 fn k() {}
 
-// CHECK: define void @l()
+// CHECK: define{{( dso_local)?}} void @l()
 #[no_mangle]
 #[inline(always)]
 pub fn l() {}