Remove PrintBackendInfo trait

It is only implemented for a single type. Directly passing this type is
simpler and avoids overhead from indirect calls.

compiler/rustc_codegen_llvm/src/lib.rs

@@ -274,10 +274,11 @@ impl CodegenBackend for LlvmCodegenBackend {
             |tcx, ()| llvm_util::global_llvm_features(tcx.sess, true)
     }
 
-    fn print(&self, req: &PrintRequest, out: &mut dyn PrintBackendInfo, sess: &Session) {
+    fn print(&self, req: &PrintRequest, out: &mut String, sess: &Session) {
+        use std::fmt::Write;
         match req.kind {
             PrintKind::RelocationModels => {
-                writeln!(out, "Available relocation models:");
+                writeln!(out, "Available relocation models:").unwrap();
                 for name in &[
                     "static",
                     "pic",
@@ -288,25 +289,25 @@ impl CodegenBackend for LlvmCodegenBackend {
                     "ropi-rwpi",
                     "default",
                 ] {
-                    writeln!(out, "    {name}");
+                    writeln!(out, "    {name}").unwrap();
                 }
-                writeln!(out);
+                writeln!(out).unwrap();
             }
             PrintKind::CodeModels => {
-                writeln!(out, "Available code models:");
+                writeln!(out, "Available code models:").unwrap();
                 for name in &["tiny", "small", "kernel", "medium", "large"] {
-                    writeln!(out, "    {name}");
+                    writeln!(out, "    {name}").unwrap();
                 }
-                writeln!(out);
+                writeln!(out).unwrap();
             }
             PrintKind::TlsModels => {
-                writeln!(out, "Available TLS models:");
+                writeln!(out, "Available TLS models:").unwrap();
                 for name in
                     &["global-dynamic", "local-dynamic", "initial-exec", "local-exec", "emulated"]
                 {
-                    writeln!(out, "    {name}");
+                    writeln!(out, "    {name}").unwrap();
                 }
-                writeln!(out);
+                writeln!(out).unwrap();
             }
             PrintKind::StackProtectorStrategies => {
                 writeln!(
@@ -332,7 +333,8 @@ impl CodegenBackend for LlvmCodegenBackend {
     none
         Do not generate stack canaries.
 "#
-                );
+                )
+                .unwrap();
             }
             _other => llvm_util::print(req, out, sess),
         }

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -6,7 +6,6 @@ use crate::errors::{
 use crate::llvm;
 use libc::c_int;
 use rustc_codegen_ssa::base::wants_wasm_eh;
-use rustc_codegen_ssa::traits::PrintBackendInfo;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::small_c_str::SmallCStr;
 use rustc_fs_util::path_to_c_string;
@@ -18,6 +17,7 @@ use rustc_target::spec::{MergeFunctions, PanicStrategy};
 use rustc_target::target_features::RUSTC_SPECIFIC_FEATURES;
 
 use std::ffi::{c_char, c_void, CStr, CString};
+use std::fmt::Write;
 use std::path::Path;
 use std::ptr;
 use std::slice;
@@ -372,7 +372,7 @@ fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
     ret
 }
 
-fn print_target_features(out: &mut dyn PrintBackendInfo, sess: &Session, tm: &llvm::TargetMachine) {
+fn print_target_features(out: &mut String, sess: &Session, tm: &llvm::TargetMachine) {
     let mut llvm_target_features = llvm_target_features(tm);
     let mut known_llvm_target_features = FxHashSet::<&'static str>::default();
     let mut rustc_target_features = sess
@@ -412,24 +412,26 @@ fn print_target_features(out: &mut dyn PrintBackendInfo, sess: &Session, tm: &ll
         .max()
         .unwrap_or(0);
 
-    writeln!(out, "Features supported by rustc for this target:");
+    writeln!(out, "Features supported by rustc for this target:").unwrap();
     for (feature, desc) in &rustc_target_features {
-        writeln!(out, "    {feature:max_feature_len$} - {desc}.");
+        writeln!(out, "    {feature:max_feature_len$} - {desc}.").unwrap();
     }
-    writeln!(out, "\nCode-generation features supported by LLVM for this target:");
+    writeln!(out, "\nCode-generation features supported by LLVM for this target:").unwrap();
     for (feature, desc) in &llvm_target_features {
-        writeln!(out, "    {feature:max_feature_len$} - {desc}.");
+        writeln!(out, "    {feature:max_feature_len$} - {desc}.").unwrap();
     }
     if llvm_target_features.is_empty() {
-        writeln!(out, "    Target features listing is not supported by this LLVM version.");
+        writeln!(out, "    Target features listing is not supported by this LLVM version.")
+            .unwrap();
     }
-    writeln!(out, "\nUse +feature to enable a feature, or -feature to disable it.");
+    writeln!(out, "\nUse +feature to enable a feature, or -feature to disable it.").unwrap();
-    writeln!(out, "For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
+    writeln!(out, "For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n")
-    writeln!(out, "Code-generation features cannot be used in cfg or #[target_feature],");
+        .unwrap();
-    writeln!(out, "and may be renamed or removed in a future version of LLVM or rustc.\n");
+    writeln!(out, "Code-generation features cannot be used in cfg or #[target_feature],").unwrap();
+    writeln!(out, "and may be renamed or removed in a future version of LLVM or rustc.\n").unwrap();
 }
 
-pub(crate) fn print(req: &PrintRequest, mut out: &mut dyn PrintBackendInfo, sess: &Session) {
+pub(crate) fn print(req: &PrintRequest, mut out: &mut String, sess: &Session) {
     require_inited();
     let tm = create_informational_target_machine(sess);
     match req.kind {
@@ -440,9 +442,9 @@ pub(crate) fn print(req: &PrintRequest, mut out: &mut dyn PrintBackendInfo, sess
             let cpu_cstring = CString::new(handle_native(sess.target.cpu.as_ref()))
                 .unwrap_or_else(|e| bug!("failed to convert to cstring: {}", e));
             unsafe extern "C" fn callback(out: *mut c_void, string: *const c_char, len: usize) {
-                let out = &mut *(out as *mut &mut dyn PrintBackendInfo);
+                let out = &mut *(out as *mut &mut String);
                 let bytes = slice::from_raw_parts(string as *const u8, len);
-                write!(out, "{}", String::from_utf8_lossy(bytes));
+                write!(out, "{}", String::from_utf8_lossy(bytes)).unwrap();
             }
             unsafe {
                 llvm::LLVMRustPrintTargetCPUs(

compiler/rustc_codegen_ssa/src/traits/backend.rs

@@ -22,8 +22,6 @@ use rustc_session::{
 use rustc_span::symbol::Symbol;
 use rustc_target::abi::call::FnAbi;
 
-use std::fmt;
-
 pub trait BackendTypes {
     type Value: CodegenObject;
     type Function: CodegenObject;
@@ -62,7 +60,7 @@ pub trait CodegenBackend {
     fn locale_resource(&self) -> &'static str;
 
     fn init(&self, _sess: &Session) {}
-    fn print(&self, _req: &PrintRequest, _out: &mut dyn PrintBackendInfo, _sess: &Session) {}
+    fn print(&self, _req: &PrintRequest, _out: &mut String, _sess: &Session) {}
     fn target_features(&self, _sess: &Session, _allow_unstable: bool) -> Vec<Symbol> {
         vec![]
     }
@@ -150,19 +148,3 @@ pub trait ExtraBackendMethods:
         std::thread::Builder::new().name(name).spawn(f)
     }
 }
-
-pub trait PrintBackendInfo {
-    fn infallible_write_fmt(&mut self, args: fmt::Arguments<'_>);
-}
-
-impl PrintBackendInfo for String {
-    fn infallible_write_fmt(&mut self, args: fmt::Arguments<'_>) {
-        fmt::Write::write_fmt(self, args).unwrap();
-    }
-}
-
-impl dyn PrintBackendInfo + '_ {
-    pub fn write_fmt(&mut self, args: fmt::Arguments<'_>) {
-        self.infallible_write_fmt(args);
-    }
-}

compiler/rustc_codegen_ssa/src/traits/mod.rs

@@ -30,9 +30,7 @@ mod write;
 
 pub use self::abi::AbiBuilderMethods;
 pub use self::asm::{AsmBuilderMethods, AsmMethods, GlobalAsmOperandRef, InlineAsmOperandRef};
-pub use self::backend::{
+pub use self::backend::{Backend, BackendTypes, CodegenBackend, ExtraBackendMethods};
-    Backend, BackendTypes, CodegenBackend, ExtraBackendMethods, PrintBackendInfo,
-};
 pub use self::builder::{BuilderMethods, OverflowOp};
 pub use self::consts::ConstMethods;
 pub use self::coverageinfo::CoverageInfoBuilderMethods;