Rollup merge of #126803 - tgross35:verbose-asm, r=Amanieu

Change `asm-comments` to `verbose-asm`, always emit user comments

Implements what is described in https://github.com/rust-lang/compiler-team/issues/762

Tracking issue: https://github.com/rust-lang/rust/issues/126802

compiler/rustc_codegen_llvm/src/back/owned_target_machine.rs

@@ -32,7 +32,7 @@ impl OwnedTargetMachine {
         unique_section_names: bool,
         trap_unreachable: bool,
         singletree: bool,
-        asm_comments: bool,
+        verbose_asm: bool,
         emit_stack_size_section: bool,
         relax_elf_relocations: bool,
         use_init_array: bool,
@@ -64,7 +64,7 @@ impl OwnedTargetMachine {
                 unique_section_names,
                 trap_unreachable,
                 singletree,
-                asm_comments,
+                verbose_asm,
                 emit_stack_size_section,
                 relax_elf_relocations,
                 use_init_array,

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -214,7 +214,7 @@ pub fn target_machine_factory(
         sess.opts.unstable_opts.trap_unreachable.unwrap_or(sess.target.trap_unreachable);
     let emit_stack_size_section = sess.opts.unstable_opts.emit_stack_sizes;
 
-    let asm_comments = sess.opts.unstable_opts.asm_comments;
+    let verbose_asm = sess.opts.unstable_opts.verbose_asm;
     let relax_elf_relocations =
         sess.opts.unstable_opts.relax_elf_relocations.unwrap_or(sess.target.relax_elf_relocations);
 
@@ -289,7 +289,7 @@ pub fn target_machine_factory(
             funique_section_names,
             trap_unreachable,
             singlethread,
-            asm_comments,
+            verbose_asm,
             emit_stack_size_section,
             relax_elf_relocations,
             use_init_array,

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2185,7 +2185,7 @@ extern "C" {
         UniqueSectionNames: bool,
         TrapUnreachable: bool,
         Singlethread: bool,
-        AsmComments: bool,
+        VerboseAsm: bool,
         EmitStackSizeSection: bool,
         RelaxELFRelocations: bool,
         UseInitArray: bool,

compiler/rustc_interface/src/tests.rs

@@ -757,7 +757,6 @@ fn test_unstable_options_tracking_hash() {
     // tidy-alphabetical-start
     tracked!(allow_features, Some(vec![String::from("lang_items")]));
     tracked!(always_encode_mir, true);
-    tracked!(asm_comments, true);
     tracked!(assume_incomplete_release, true);
     tracked!(binary_dep_depinfo, true);
     tracked!(box_noalias, false);
@@ -862,6 +861,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(uninit_const_chunk_threshold, 123);
     tracked!(unleash_the_miri_inside_of_you, true);
     tracked!(use_ctors_section, Some(true));
+    tracked!(verbose_asm, true);
     tracked!(verify_llvm_ir, true);
     tracked!(virtual_function_elimination, true);
     tracked!(wasi_exec_model, Some(WasiExecModel::Reactor));

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -407,7 +407,7 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
     const char *ABIStr, LLVMRustCodeModel RustCM, LLVMRustRelocModel RustReloc,
     LLVMRustCodeGenOptLevel RustOptLevel, bool UseSoftFloat,
     bool FunctionSections, bool DataSections, bool UniqueSectionNames,
-    bool TrapUnreachable, bool Singlethread, bool AsmComments,
+    bool TrapUnreachable, bool Singlethread, bool VerboseAsm,
     bool EmitStackSizeSection, bool RelaxELFRelocations, bool UseInitArray,
     const char *SplitDwarfFile, const char *OutputObjFile,
     const char *DebugInfoCompression, bool UseEmulatedTls,
@@ -435,8 +435,9 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
   Options.DataSections = DataSections;
   Options.FunctionSections = FunctionSections;
   Options.UniqueSectionNames = UniqueSectionNames;
-  Options.MCOptions.AsmVerbose = AsmComments;
+  Options.MCOptions.AsmVerbose = VerboseAsm;
-  Options.MCOptions.PreserveAsmComments = AsmComments;
+  // Always preserve comments that were written by the user
+  Options.MCOptions.PreserveAsmComments = true;
   Options.MCOptions.ABIName = ABIStr;
   if (SplitDwarfFile) {
     Options.MCOptions.SplitDwarfFile = SplitDwarfFile;

compiler/rustc_session/src/options.rs

@@ -1630,8 +1630,6 @@ options! {
         "only allow the listed language features to be enabled in code (comma separated)"),
     always_encode_mir: bool = (false, parse_bool, [TRACKED],
         "encode MIR of all functions into the crate metadata (default: no)"),
-    asm_comments: bool = (false, parse_bool, [TRACKED],
-        "generate comments into the assembly (may change behavior) (default: no)"),
     assert_incr_state: Option<String> = (None, parse_opt_string, [UNTRACKED],
         "assert that the incremental cache is in given state: \
          either `loaded` or `not-loaded`."),
@@ -2107,6 +2105,8 @@ written to standard error output)"),
         "Generate sync unwind tables instead of async unwind tables (default: no)"),
     validate_mir: bool = (false, parse_bool, [UNTRACKED],
         "validate MIR after each transformation"),
+    verbose_asm: bool = (false, parse_bool, [TRACKED],
+        "add descriptive comments from LLVM to the assembly (may change behavior) (default: no)"),
     #[rustc_lint_opt_deny_field_access("use `Session::verbose_internals` instead of this field")]
     verbose_internals: bool = (false, parse_bool, [TRACKED_NO_CRATE_HASH],
         "in general, enable more debug printouts (default: no)"),

src/doc/unstable-book/src/compiler-flags/verbose-asm.md

@@ -0,0 +1,70 @@
+# `verbose-asm`
+
+The tracking issue for this feature is: [#126802](https://github.com/rust-lang/rust/issues/126802).
+
+------------------------
+
+This enables passing `-Zverbose-asm` to get contextual comments added by LLVM.
+
+Sample code:
+
+```rust
+#[no_mangle]
+pub fn foo(a: i32, b: i32) -> i32 {
+    a + b
+}
+```
+
+Default output:
+
+```asm
+foo:
+        push    rax
+        add     edi, esi
+        mov     dword ptr [rsp + 4], edi
+        seto    al
+        jo      .LBB0_2
+        mov     eax, dword ptr [rsp + 4]
+        pop     rcx
+        ret
+.LBB0_2:
+        lea     rdi, [rip + .L__unnamed_1]
+        mov     rax, qword ptr [rip + core::panicking::panic_const::panic_const_add_overflow::h9c85248fe0d735b2@GOTPCREL]
+        call    rax
+
+.L__unnamed_2:
+        .ascii  "/app/example.rs"
+
+.L__unnamed_1:
+        .quad   .L__unnamed_2
+        .asciz  "\017\000\000\000\000\000\000\000\004\000\000\000\005\000\000"
+```
+
+With `-Zverbose-asm`:
+
+```asm
+foo:                                    # @foo
+# %bb.0:
+        push    rax
+        add     edi, esi
+        mov     dword ptr [rsp + 4], edi        # 4-byte Spill
+        seto    al
+        jo      .LBB0_2
+# %bb.1:
+        mov     eax, dword ptr [rsp + 4]        # 4-byte Reload
+        pop     rcx
+        ret
+.LBB0_2:
+        lea     rdi, [rip + .L__unnamed_1]
+        mov     rax, qword ptr [rip + core::panicking::panic_const::panic_const_add_overflow::h9c85248fe0d735b2@GOTPCREL]
+        call    rax
+                                        # -- End function
+.L__unnamed_2:
+        .ascii  "/app/example.rs"
+
+.L__unnamed_1:
+        .quad   .L__unnamed_2
+        .asciz  "\017\000\000\000\000\000\000\000\004\000\000\000\005\000\000"
+
+                                        # DW_AT_external
+```

tests/assembly/asm-comments.rs

@@ -0,0 +1,12 @@
+//@ assembly-output: emit-asm
+//@ only-x86_64
+// Check that comments in assembly get passed
+
+#![crate_type = "lib"]
+
+// CHECK-LABEL: test_comments:
+#[no_mangle]
+pub fn test_comments() {
+    // CHECK: example comment
+    unsafe { core::arch::asm!("nop // example comment") };
+}