make -Zmin-function-alignment a target modifier

compiler/rustc_session/src/options.rs

@@ -2340,7 +2340,7 @@ options! {
         "gather metadata statistics (default: no)"),
     metrics_dir: Option<PathBuf> = (None, parse_opt_pathbuf, [UNTRACKED],
         "the directory metrics emitted by rustc are dumped into (implicitly enables default set of metrics)"),
-    min_function_alignment: Option<Align> = (None, parse_align, [TRACKED],
+    min_function_alignment: Option<Align> = (None, parse_align, [TRACKED TARGET_MODIFIER],
         "align all functions to at least this many bytes. Must be a power of 2"),
     mir_emit_retag: bool = (false, parse_bool, [TRACKED],
         "emit Retagging MIR statements, interpreted e.g., by miri; implies -Zmir-opt-level=0 \

src/tools/miri/tests/pass/fn_align.rs

@@ -1,4 +1,4 @@
-//@compile-flags: -Zmin-function-alignment=8
+//@compile-flags: -Zmin-function-alignment=8 -Cunsafe-allow-abi-mismatch=min-function-alignment
 #![feature(fn_align)]
 
 // When a function uses `align(N)`, the function address should be a multiple of `N`.

tests/codegen/min-function-alignment.rs

@@ -1,10 +1,17 @@
+//@ add-core-stubs
 //@ revisions: align16 align1024
 //@ compile-flags: -C no-prepopulate-passes -Z mir-opt-level=0 -Clink-dead-code
 //@ [align16] compile-flags: -Zmin-function-alignment=16
 //@ [align1024] compile-flags: -Zmin-function-alignment=1024
 
-#![crate_type = "lib"]
+#![feature(no_core)]
 #![feature(fn_align)]
+#![crate_type = "lib"]
+#![no_std]
+#![no_core]
+
+extern crate minicore;
+use minicore::*;
 
 // Functions without explicit alignment use the global minimum.
 //

tests/codegen/naked-fn/min-function-alignment.rs

@@ -1,33 +1,40 @@
+//@ add-core-stubs
 //@ compile-flags: -C no-prepopulate-passes -Copt-level=0 -Zmin-function-alignment=16
 //@ needs-asm-support
 //@ ignore-arm no "ret" mnemonic
 
+#![feature(no_core)]
 #![feature(fn_align)]
 #![crate_type = "lib"]
+#![no_std]
+#![no_core]
+
+extern crate minicore;
+use minicore::*;
 
 // functions without explicit alignment use the global minimum
 //
 // CHECK: .balign 16
 #[no_mangle]
 #[unsafe(naked)]
 pub extern "C" fn naked_no_explicit_align() {
-    core::arch::naked_asm!("ret")
+    naked_asm!("ret")
 }
 
 // CHECK: .balign 16
 #[no_mangle]
 #[align(8)]
 #[unsafe(naked)]
 pub extern "C" fn naked_lower_align() {
-    core::arch::naked_asm!("ret")
+    naked_asm!("ret")
 }
 
 // CHECK: .balign 32
 #[no_mangle]
 #[align(32)]
 #[unsafe(naked)]
 pub extern "C" fn naked_higher_align() {
-    core::arch::naked_asm!("ret")
+    naked_asm!("ret")
 }
 
 // cold functions follow the same rules as other functions
@@ -40,5 +47,5 @@ pub extern "C" fn naked_higher_align() {
 #[cold]
 #[unsafe(naked)]
 pub extern "C" fn no_explicit_align_cold() {
-    core::arch::naked_asm!("ret")
+    naked_asm!("ret")
 }

tests/ui/target_modifiers/auxiliary/min_function_alignment.rs

@@ -0,0 +1,7 @@
+//@ no-prefer-dynamic
+//@ compile-flags: --target aarch64-unknown-none -Zmin-function-alignment=32
+//@ needs-llvm-components: aarch64
+
+#![feature(no_core)]
+#![crate_type = "rlib"]
+#![no_core]

tests/ui/target_modifiers/incompatible_min_function_alignment.error_mismatch.stderr

@@ -0,0 +1,13 @@
+error: mixing `-Zmin-function-alignment` will cause an ABI mismatch in crate `incompatible_min_function_alignment`
+  --> $DIR/incompatible_min_function_alignment.rs:13:1
+   |
+LL | #![feature(no_core)]
+   | ^
+   |
+   = help: the `-Zmin-function-alignment` flag modifies the ABI so Rust crates compiled with different values of this flag cannot be used together safely
+   = note: `-Zmin-function-alignment=4` in this crate is incompatible with `-Zmin-function-alignment=32` in dependency `min_function_alignment`
+   = help: set `-Zmin-function-alignment=32` in this crate or `-Zmin-function-alignment=4` in `min_function_alignment`
+   = help: if you are sure this will not cause problems, you may use `-Cunsafe-allow-abi-mismatch=min-function-alignment` to silence this error
+
+error: aborting due to 1 previous error
+

tests/ui/target_modifiers/incompatible_min_function_alignment.error_omitted.stderr

@@ -0,0 +1,13 @@
+error: mixing `-Zmin-function-alignment` will cause an ABI mismatch in crate `incompatible_min_function_alignment`
+  --> $DIR/incompatible_min_function_alignment.rs:13:1
+   |
+LL | #![feature(no_core)]
+   | ^
+   |
+   = help: the `-Zmin-function-alignment` flag modifies the ABI so Rust crates compiled with different values of this flag cannot be used together safely
+   = note: unset `-Zmin-function-alignment` in this crate is incompatible with `-Zmin-function-alignment=32` in dependency `min_function_alignment`
+   = help: set `-Zmin-function-alignment=32` in this crate or unset `-Zmin-function-alignment` in `min_function_alignment`
+   = help: if you are sure this will not cause problems, you may use `-Cunsafe-allow-abi-mismatch=min-function-alignment` to silence this error
+
+error: aborting due to 1 previous error
+

tests/ui/target_modifiers/incompatible_min_function_alignment.rs

@@ -0,0 +1,18 @@
+//@ aux-build:min_function_alignment.rs
+//@ compile-flags: --target aarch64-unknown-none
+//@ needs-llvm-components: aarch64
+
+//@ revisions:allow_match allow_mismatch error_mismatch error_omitted
+//@[allow_match] compile-flags: -Zmin-function-alignment=32
+//@[allow_mismatch] compile-flags: -Cunsafe-allow-abi-mismatch=min-function-alignment
+//@[error_mismatch] compile-flags: -Zmin-function-alignment=4
+//@[error_omitted] compile-flags:
+//@[allow_mismatch] check-pass
+//@[allow_match] check-pass
+
+#![feature(no_core)]
+//[error_mismatch,error_omitted]~^ ERROR mixing `-Zmin-function-alignment` will cause an ABI mismatch in crate `incompatible_min_function_alignment`
+#![crate_type = "rlib"]
+#![no_core]
+
+extern crate min_function_alignment;