Rollup merge of #82270 - asquared31415:asm-syntax-directive-errors, r=nagisa

Emit error when trying to use assembler syntax directives in `asm!`

The `.intel_syntax` and `.att_syntax` assembler directives should not be used, in favor of not specifying a syntax for intel, and in favor of the explicit `att_syntax` option using the inline assembly options.

Closes #79869

src/test/ui/asm/inline-syntax.arm.stderr

@@ -0,0 +1,14 @@
+error: att syntax is the default syntax on this target, and trying to use this directive may cause issues
+  --> $DIR/inline-syntax.rs:22:15
+   |
+LL |         asm!(".att_syntax noprefix", "nop");
+   |               ^^^^^^^^^^^^^^^^^^^^ help: remove this assembler directive
+
+error: att syntax is the default syntax on this target, and trying to use this directive may cause issues
+  --> $DIR/inline-syntax.rs:25:15
+   |
+LL |         asm!(".att_syntax bbb noprefix", "nop");
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^ help: remove this assembler directive
+
+error: aborting due to 2 previous errors
+

src/test/ui/asm/inline-syntax.rs

@@ -0,0 +1,38 @@
+// revisions: x86_64 arm
+//[x86_64] compile-flags: --target x86_64-unknown-linux-gnu
+//[arm] compile-flags: --target armv7-unknown-linux-gnueabihf
+
+#![feature(no_core, lang_items, rustc_attrs)]
+#![no_core]
+
+#[rustc_builtin_macro]
+macro_rules! asm {
+    () => {};
+}
+
+#[lang = "sized"]
+trait Sized {}
+
+fn main() {
+    unsafe {
+        asm!(".intel_syntax noprefix", "nop");
+        //[x86_64]~^ ERROR intel syntax is the default syntax on this target
+        asm!(".intel_syntax aaa noprefix", "nop");
+        //[x86_64]~^ ERROR intel syntax is the default syntax on this target
+        asm!(".att_syntax noprefix", "nop");
+        //[x86_64]~^ ERROR using the .att_syntax directive may cause issues
+        //[arm]~^^ att syntax is the default syntax on this target
+        asm!(".att_syntax bbb noprefix", "nop");
+        //[x86_64]~^ ERROR using the .att_syntax directive may cause issues
+        //[arm]~^^ att syntax is the default syntax on this target
+        asm!(".intel_syntax noprefix; nop");
+        //[x86_64]~^ ERROR intel syntax is the default syntax on this target
+
+        asm!(
+            r"
+            .intel_syntax noprefix
+            nop"
+        );
+        //[x86_64]~^^^ ERROR intel syntax is the default syntax on this target
+    }
+}

src/test/ui/asm/inline-syntax.x86_64.stderr

@@ -0,0 +1,50 @@
+error: intel syntax is the default syntax on this target, and trying to use this directive may cause issues
+  --> $DIR/inline-syntax.rs:18:15
+   |
+LL |         asm!(".intel_syntax noprefix", "nop");
+   |               ^^^^^^^^^^^^^^^^^^^^^^ help: remove this assembler directive
+
+error: intel syntax is the default syntax on this target, and trying to use this directive may cause issues
+  --> $DIR/inline-syntax.rs:20:15
+   |
+LL |         asm!(".intel_syntax aaa noprefix", "nop");
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove this assembler directive
+
+error: using the .att_syntax directive may cause issues, use the att_syntax option instead
+  --> $DIR/inline-syntax.rs:22:15
+   |
+LL |         asm!(".att_syntax noprefix", "nop");
+   |               ^^^^^^^^^^^^^^^^^^^^
+   |
+help: remove the assembler directive and replace it with options(att_syntax)
+   |
+LL |         asm!("", "nop", options(att_syntax));
+   |              --       ^^^^^^^^^^^^^^^^^^^^^
+
+error: using the .att_syntax directive may cause issues, use the att_syntax option instead
+  --> $DIR/inline-syntax.rs:25:15
+   |
+LL |         asm!(".att_syntax bbb noprefix", "nop");
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: remove the assembler directive and replace it with options(att_syntax)
+   |
+LL |         asm!("", "nop", options(att_syntax));
+   |              --       ^^^^^^^^^^^^^^^^^^^^^
+
+error: intel syntax is the default syntax on this target, and trying to use this directive may cause issues
+  --> $DIR/inline-syntax.rs:28:15
+   |
+LL |         asm!(".intel_syntax noprefix; nop");
+   |               ^^^^^^^^^^^^^^^^^^^^^^ help: remove this assembler directive
+
+error: intel syntax is the default syntax on this target, and trying to use this directive may cause issues
+  --> $DIR/inline-syntax.rs:33:14
+   |
+LL |               .intel_syntax noprefix
+   |  ______________^
+LL | |             nop"
+   | |_ help: remove this assembler directive
+
+error: aborting due to 6 previous errors
+