Auto merge of #128004 - folkertdev:naked-fn-asm, r=Amanieu

codegen `#[naked]` functions using global asm

tracking issue: https://github.com/rust-lang/rust/issues/90957

Fixes #124375

This implements the approach suggested in the tracking issue: use the existing global assembly infrastructure to emit the body of `#[naked]` functions. The main advantage is that we now have full control over what gets generated, and are no longer dependent on LLVM not sneakily messing with our output (inlining, adding extra instructions, etc).

I discussed this approach with `@Amanieu` and while I think the general direction is correct, there is probably a bunch of stuff that needs to change or move around here. I'll leave some inline comments on things that I'm not sure about.

Combined with https://github.com/rust-lang/rust/pull/127853, if both accepted, I think that resolves all steps from the tracking issue.

r? `@Amanieu`

7 files changed, 318 insertions, 77 deletions

diff --git a/tests/codegen/naked-asan.rs b/tests/codegen/naked-asan.rs
index bcaa60baeff..8efedab6ea5 100644
--- a/tests/codegen/naked-asan.rs
+++ b/tests/codegen/naked-asan.rs
@@ -8,14 +8,15 @@
 #![no_std]
 #![feature(abi_x86_interrupt, naked_functions)]
 
-// CHECK: define x86_intrcc void @page_fault_handler(ptr {{.*}}%0, i64 {{.*}}%1){{.*}}#[[ATTRS:[0-9]+]] {
-// CHECK-NOT: memcpy
+pub fn caller() {
+    page_fault_handler(1, 2);
+}
+
+// CHECK: declare x86_intrcc void @page_fault_handler(ptr {{.*}}, i64{{.*}}){{.*}}#[[ATTRS:[0-9]+]]
 #[naked]
 #[no_mangle]
 pub extern "x86-interrupt" fn page_fault_handler(_: u64, _: u64) {
-    unsafe {
-        core::arch::naked_asm!("ud2");
-    }
+    unsafe { core::arch::naked_asm!("ud2") };
 }
 
 // CHECK: #[[ATTRS]] =
diff --git a/tests/codegen/naked-fn/aligned.rs b/tests/codegen/naked-fn/aligned.rs
index 3bbd67981e5..d9dcd7f6c3e 100644
--- a/tests/codegen/naked-fn/aligned.rs
+++ b/tests/codegen/naked-fn/aligned.rs
@@ -6,15 +6,12 @@
 #![feature(naked_functions, fn_align)]
 use std::arch::naked_asm;
 
-// CHECK: Function Attrs: naked
-// CHECK-NEXT: define{{.*}}void @naked_empty()
-// CHECK: align 16
+// CHECK: .balign 16
+// CHECK-LABEL: naked_empty:
 #[repr(align(16))]
 #[no_mangle]
 #[naked]
 pub unsafe extern "C" fn naked_empty() {
-    // CHECK-NEXT: start:
-    // CHECK-NEXT: call void asm
-    // CHECK-NEXT: unreachable
+    // CHECK: ret
     naked_asm!("ret");
 }
diff --git a/tests/codegen/naked-fn/generics.rs b/tests/codegen/naked-fn/generics.rs
new file mode 100644
index 00000000000..a33d213617a
--- /dev/null
+++ b/tests/codegen/naked-fn/generics.rs
@@ -0,0 +1,116 @@
+//@ compile-flags: -O
+//@ only-x86_64
+
+#![crate_type = "lib"]
+#![feature(naked_functions, asm_const)]
+
+use std::arch::naked_asm;
+
+#[no_mangle]
+fn test(x: u64) {
+    // just making sure these symbols get used
+    using_const_generics::<1>(x);
+    using_const_generics::<2>(x);
+
+    generic_function::<i64>(x as i64);
+
+    let foo = Foo(x);
+
+    foo.method();
+    foo.trait_method();
+}
+
+// CHECK: .balign 4
+// CHECK: add rax, 2
+// CHECK: add rax, 42
+
+// CHECK: .balign 4
+// CHECK: add rax, 1
+// CHECK: add rax, 42
+
+#[naked]
+pub extern "C" fn using_const_generics<const N: u64>(x: u64) -> u64 {
+    const M: u64 = 42;
+
+    unsafe {
+        naked_asm!(
+            "xor rax, rax",
+            "add rax, rdi",
+            "add rax, {}",
+            "add rax, {}",
+            "ret",
+            const N,
+            const M,
+        )
+    }
+}
+
+trait Invert {
+    fn invert(self) -> Self;
+}
+
+impl Invert for i64 {
+    fn invert(self) -> Self {
+        -1 * self
+    }
+}
+
+// CHECK: .balign 4
+// CHECK-LABEL: generic_function:
+// CHECK: call
+// CHECK: ret
+
+#[naked]
+#[no_mangle]
+pub extern "C" fn generic_function<T: Invert>(x: i64) -> i64 {
+    unsafe {
+        naked_asm!(
+            "call {}",
+            "ret",
+            sym <T as Invert>::invert,
+        )
+    }
+}
+
+#[derive(Copy, Clone)]
+#[repr(transparent)]
+struct Foo(u64);
+
+// CHECK: .balign 4
+// CHECK-LABEL: method:
+// CHECK: mov rax, rdi
+
+impl Foo {
+    #[naked]
+    #[no_mangle]
+    extern "C" fn method(self) -> u64 {
+        unsafe { naked_asm!("mov rax, rdi", "ret") }
+    }
+}
+
+// CHECK: .balign 4
+// CHECK-LABEL: trait_method:
+// CHECK: mov rax, rdi
+
+trait Bar {
+    extern "C" fn trait_method(self) -> u64;
+}
+
+impl Bar for Foo {
+    #[naked]
+    #[no_mangle]
+    extern "C" fn trait_method(self) -> u64 {
+        unsafe { naked_asm!("mov rax, rdi", "ret") }
+    }
+}
+
+// CHECK: .balign 4
+// CHECK-LABEL: naked_with_args_and_return:
+// CHECK: lea rax, [rdi + rsi]
+
+// this previously ICE'd, see https://github.com/rust-lang/rust/issues/124375
+#[naked]
+#[no_mangle]
+pub unsafe extern "C" fn naked_with_args_and_return(a: isize, b: isize) -> isize {
+    naked_asm!("lea rax, [rdi + rsi]", "ret");
+}
diff --git a/tests/codegen/naked-fn/instruction-set.rs b/tests/codegen/naked-fn/instruction-set.rs
new file mode 100644
index 00000000000..5b790b2034c
--- /dev/null
+++ b/tests/codegen/naked-fn/instruction-set.rs
@@ -0,0 +1,59 @@
+//@ revisions: arm-mode thumb-mode
+//@ [arm-mode] compile-flags: --target armv5te-none-eabi
+//@ [thumb-mode] compile-flags: --target thumbv5te-none-eabi
+//@ [arm-mode] needs-llvm-components: arm
+//@ [thumb-mode] needs-llvm-components: arm
+
+#![crate_type = "lib"]
+#![feature(no_core, lang_items, rustc_attrs, naked_functions)]
+#![no_core]
+
+#[rustc_builtin_macro]
+macro_rules! naked_asm {
+    () => {};
+}
+
+#[lang = "sized"]
+trait Sized {}
+#[lang = "copy"]
+trait Copy {}
+
+// arm-mode: .arm
+// thumb-mode: .thumb
+// CHECK-LABEL: test_unspecified:
+// CHECK: bx lr
+// CHECK: .popsection
+// arm-mode: .arm
+// thumb-mode: .thumb
+#[no_mangle]
+#[naked]
+unsafe extern "C" fn test_unspecified() {
+    naked_asm!("bx lr");
+}
+
+// CHECK: .thumb
+// CHECK: .thumb_func
+// CHECK-LABEL: test_thumb:
+// CHECK: bx lr
+// CHECK: .popsection
+// arm-mode: .arm
+// thumb-mode: .thumb
+#[no_mangle]
+#[naked]
+#[instruction_set(arm::t32)]
+unsafe extern "C" fn test_thumb() {
+    naked_asm!("bx lr");
+}
+
+// CHECK: .arm
+// CHECK-LABEL: test_arm:
+// CHECK: bx lr
+// CHECK: .popsection
+// arm-mode: .arm
+// thumb-mode: .thumb
+#[no_mangle]
+#[naked]
+#[instruction_set(arm::a32)]
+unsafe extern "C" fn test_arm() {
+    naked_asm!("bx lr");
+}
diff --git a/tests/codegen/naked-fn/naked-functions.rs b/tests/codegen/naked-fn/naked-functions.rs
index 3f7447af599..f505d27d48c 100644
--- a/tests/codegen/naked-fn/naked-functions.rs
+++ b/tests/codegen/naked-fn/naked-functions.rs
@@ -1,29 +1,147 @@
-//@ compile-flags: -C no-prepopulate-passes -Copt-level=0
-//@ needs-asm-support
-//@ only-x86_64
+//@ revisions: linux win macos thumb
+//
+//@[linux] compile-flags: --target x86_64-unknown-linux-gnu
+//@[linux] needs-llvm-components: x86
+//@[win] compile-flags: --target x86_64-pc-windows-gnu
+//@[win] needs-llvm-components: x86
+//@[macos] compile-flags: --target aarch64-apple-darwin
+//@[macos] needs-llvm-components: arm
+//@[thumb] compile-flags: --target thumbv7em-none-eabi
+//@[thumb] needs-llvm-components: arm
 
 #![crate_type = "lib"]
-#![feature(naked_functions)]
-use std::arch::naked_asm;
+#![feature(no_core, lang_items, rustc_attrs, naked_functions)]
+#![no_core]
+
+#[rustc_builtin_macro]
+macro_rules! naked_asm {
+    () => {};
+}
+
+#[lang = "sized"]
+trait Sized {}
+#[lang = "copy"]
+trait Copy {}
+
+// linux,win: .intel_syntax
+//
+// linux:   .pushsection .text.naked_empty,\22ax\22, @progbits
+// macos:   .pushsection __TEXT,__text,regular,pure_instructions
+// win: .pushsection .text.naked_empty,\22xr\22
+// thumb:   .pushsection .text.naked_empty,\22ax\22, %progbits
+//
+// CHECK: .balign 4
+//
+// linux,win,thumb: .globl naked_empty
+// macos: .globl _naked_empty
+//
+// CHECK-NOT: .private_extern
+// CHECK-NOT: .hidden
+//
+// linux: .type naked_empty, @function
+//
+// win: .def naked_empty
+// win: .scl 2
+// win: .type 32
+// win: .endef naked_empty
+//
+// thumb: .type naked_empty, %function
+// thumb: .thumb
+// thumb: .thumb_func
+//
+// CHECK-LABEL: naked_empty:
+//
+// linux,macos,win: ret
+// thumb: bx lr
+//
+// CHECK: .popsection
+//
+// thumb: .thumb
+//
+// linux,win: .att_syntax
 
-// CHECK: Function Attrs: naked
-// CHECK-NEXT: define{{.*}}void @naked_empty()
 #[no_mangle]
 #[naked]
 pub unsafe extern "C" fn naked_empty() {
-    // CHECK-NEXT: {{.+}}:
-    // CHECK-NEXT: call void asm
-    // CHECK-NEXT: unreachable
+    #[cfg(not(all(target_arch = "arm", target_feature = "thumb-mode")))]
     naked_asm!("ret");
+
+    #[cfg(all(target_arch = "arm", target_feature = "thumb-mode"))]
+    naked_asm!("bx lr");
 }
 
-// CHECK: Function Attrs: naked
-// CHECK-NEXT: define{{.*}}i{{[0-9]+}} @naked_with_args_and_return(i64 %0, i64 %1)
+// linux,win: .intel_syntax
+//
+// linux:   .pushsection .text.naked_with_args_and_return,\22ax\22, @progbits
+// macos:   .pushsection __TEXT,__text,regular,pure_instructions
+// win: .pushsection .text.naked_with_args_and_return,\22xr\22
+// thumb:   .pushsection .text.naked_with_args_and_return,\22ax\22, %progbits
+//
+// CHECK: .balign 4
+//
+// linux,win,thumb: .globl naked_with_args_and_return
+// macos: .globl _naked_with_args_and_return
+//
+// CHECK-NOT: .private_extern
+// CHECK-NOT: .hidden
+//
+// linux: .type naked_with_args_and_return, @function
+//
+// win: .def naked_with_args_and_return
+// win: .scl 2
+// win: .type 32
+// win: .endef naked_with_args_and_return
+//
+// thumb: .type naked_with_args_and_return, %function
+// thumb: .thumb
+// thumb: .thumb_func
+//
+// CHECK-LABEL: naked_with_args_and_return:
+//
+// linux, win: lea rax, [rdi + rsi]
+// macos: add x0, x0, x1
+// thumb: adds r0, r0, r1
+//
+// linux,macos,win: ret
+// thumb: bx lr
+//
+// CHECK: .popsection
+//
+// thumb: .thumb
+//
+// linux,win: .att_syntax
+
 #[no_mangle]
 #[naked]
 pub unsafe extern "C" fn naked_with_args_and_return(a: isize, b: isize) -> isize {
-    // CHECK-NEXT: {{.+}}:
-    // CHECK-NEXT: call void asm
-    // CHECK-NEXT: unreachable
-    naked_asm!("lea rax, [rdi + rsi]", "ret");
+    #[cfg(any(target_os = "windows", target_os = "linux"))]
+    {
+        naked_asm!("lea rax, [rdi + rsi]", "ret")
+    }
+
+    #[cfg(target_os = "macos")]
+    {
+        naked_asm!("add x0, x0, x1", "ret")
+    }
+
+    #[cfg(all(target_arch = "arm", target_feature = "thumb-mode"))]
+    {
+        naked_asm!("adds r0, r0, r1", "bx lr")
+    }
+}
+
+// linux:   .pushsection .text.some_different_name,\22ax\22, @progbits
+// macos:   .pushsection .text.some_different_name,regular,pure_instructions
+// win: .pushsection .text.some_different_name,\22xr\22
+// thumb:   .pushsection .text.some_different_name,\22ax\22, %progbits
+// CHECK-LABEL: test_link_section:
+#[no_mangle]
+#[naked]
+#[link_section = ".text.some_different_name"]
+pub unsafe extern "C" fn test_link_section() {
+    #[cfg(not(all(target_arch = "arm", target_feature = "thumb-mode")))]
+    naked_asm!("ret");
+
+    #[cfg(all(target_arch = "arm", target_feature = "thumb-mode"))]
+    naked_asm!("bx lr");
 }
diff --git a/tests/codegen/naked-fn/naked-nocoverage.rs b/tests/codegen/naked-fn/naked-nocoverage.rs
deleted file mode 100644
index f63661bcd3a..00000000000
--- a/tests/codegen/naked-fn/naked-nocoverage.rs
+++ /dev/null
@@ -1,19 +0,0 @@
-// Checks that naked functions are not instrumented by -Cinstrument-coverage.
-// Regression test for issue #105170.
-//
-//@ needs-asm-support
-//@ compile-flags: -Zno-profiler-runtime
-//@ compile-flags: -Cinstrument-coverage
-#![crate_type = "lib"]
-#![feature(naked_functions)]
-use std::arch::naked_asm;
-
-#[naked]
-#[no_mangle]
-pub unsafe extern "C" fn f() {
-    // CHECK:       define {{(dso_local )?}}void @f()
-    // CHECK-NEXT:  start:
-    // CHECK-NEXT:    call void asm
-    // CHECK-NEXT:    unreachable
-    naked_asm!("");
-}
diff --git a/tests/codegen/naked-fn/naked-noinline.rs b/tests/codegen/naked-fn/naked-noinline.rs
deleted file mode 100644
index 6ea36d96783..00000000000
--- a/tests/codegen/naked-fn/naked-noinline.rs
+++ /dev/null
@@ -1,31 +0,0 @@
-// Checks that naked functions are never inlined.
-//@ compile-flags: -O -Zmir-opt-level=3
-//@ needs-asm-support
-//@ ignore-wasm32
-#![crate_type = "lib"]
-#![feature(naked_functions)]
-
-use std::arch::naked_asm;
-
-#[naked]
-#[no_mangle]
-pub unsafe extern "C" fn f() {
-    // Check that f has naked and noinline attributes.
-    //
-    // CHECK:       define {{(dso_local )?}}void @f() unnamed_addr [[ATTR:#[0-9]+]]
-    // CHECK-NEXT:  start:
-    // CHECK-NEXT:    call void asm
-    naked_asm!("");
-}
-
-#[no_mangle]
-pub unsafe fn g() {
-    // Check that call to f is not inlined.
-    //
-    // CHECK-LABEL: define {{(dso_local )?}}void @g()
-    // CHECK-NEXT:  start:
-    // CHECK-NEXT:    call void @f()
-    f();
-}
-
-// CHECK: attributes [[ATTR]] = { naked{{.*}}noinline{{.*}} }