Auto merge of #71579 - Dylan-DPC:rollup-h9om2g3, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #71490 (Cleanup and document `-C relocation-model`)
 - #71562 (fix more clippy warnings)
 - #71571 (Fix since attribute for nonzero_bitor impl's)
 - #71574 (proc_macro: Fix since attributes for new Span methods)
 - #71575 (Fix stable(since) attribute for BTreeMap::remove_entry)

Failed merges:

r? @ghost

src/doc/rustc/src/codegen-options/index.md

@@ -319,11 +319,46 @@ to a valid `.profdata` file. See the chapter on
 
 ## relocation-model
 
-This option lets you choose which
-[relocation](https://en.wikipedia.org/wiki/Relocation_\(computing\)) model to
-use.
+This option controls generation of
+[position-independent code (PIC)](https://en.wikipedia.org/wiki/Position-independent_code).
 
-To find the valid options for this flag, run `rustc --print relocation-models`.
+Supported values for this option are:
+
+#### Primary relocation models
+
+- `static` - non-relocatable code, machine instructions may use absolute addressing modes.
+
+- `pic` - fully relocatable position independent code,
+machine instructions need to use relative addressing modes.  
+Equivalent to the "uppercase" `-fPIC` or `-fPIE` options in other compilers,
+depending on the produced crate types.  
+This is the default model for majority of supported targets.
+
+#### Special relocation models
+
+- `dynamic-no-pic` - relocatable external references, non-relocatable code.  
+Only makes sense on Darwin and is rarely used.  
+If StackOverflow tells you to use this as an opt-out of PIC or PIE, don't believe it,
+use `-C relocation-model=static` instead.
+- `ropi`, `rwpi` and `ropi-rwpi` - relocatable code and read-only data, relocatable read-write data,
+and combination of both, respectively.  
+Only makes sense for certain embedded ARM targets.
+- `default` - relocation model default to the current target.  
+Only makes sense as an override for some other explicitly specified relocation model
+previously set on the command line.
+
+Supported values can also be discovered by running `rustc --print relocation-models`.
+
+#### Linking effects
+
+In addition to codegen effects, `relocation-model` has effects during linking.
+
+If the relocation model is `pic` and the current target supports position-independent executables
+(PIE), the linker will be instructed (`-pie`) to produce one.  
+If the target doesn't support both position-independent and statically linked executables,
+then `-C target-feature=+crt-static` "wins" over `-C relocation-model=pic`,
+and the linker is instructed (`-static`) to produce a statically linked
+but not position-independent executable.
 
 ## remark
 

src/liballoc/collections/binary_heap.rs

@@ -1269,7 +1269,7 @@ impl<'a, T: Ord> Drop for DrainSorted<'a, T> {
 
         impl<'r, 'a, T: Ord> Drop for DropGuard<'r, 'a, T> {
             fn drop(&mut self) {
-                while let Some(_) = self.0.inner.pop() {}
+                while self.0.inner.pop().is_some() {}
             }
         }
 

src/liballoc/collections/btree/map.rs

@@ -930,7 +930,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
     /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
     /// assert_eq!(map.remove_entry(&1), None);
     /// ```
-    #[stable(feature = "btreemap_remove_entry", since = "1.44.0")]
+    #[stable(feature = "btreemap_remove_entry", since = "1.45.0")]
     pub fn remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)>
     where
         K: Borrow<Q>,

src/liballoc/collections/linked_list.rs

@@ -972,7 +972,7 @@ unsafe impl<#[may_dangle] T> Drop for LinkedList<T> {
             fn drop(&mut self) {
                 // Continue the same loop we do below. This only runs when a destructor has
                 // panicked. If another one panics this will abort.
-                while let Some(_) = self.0.pop_front_node() {}
+                while self.0.pop_front_node().is_some() {}
             }
         }
 

src/libcore/num/mod.rs

@@ -111,7 +111,7 @@ assert_eq!(size_of::<Option<core::num::", stringify!($Ty), ">>(), size_of::<", s
                 }
             }
 
-            #[stable(feature = "nonzero_bitor", since = "1.43.0")]
+            #[stable(feature = "nonzero_bitor", since = "1.45.0")]
             impl BitOr for $Ty {
                 type Output = Self;
                 #[inline]
@@ -122,7 +122,7 @@ assert_eq!(size_of::<Option<core::num::", stringify!($Ty), ">>(), size_of::<", s
                 }
             }
 
-            #[stable(feature = "nonzero_bitor", since = "1.43.0")]
+            #[stable(feature = "nonzero_bitor", since = "1.45.0")]
             impl BitOr<$Int> for $Ty {
                 type Output = Self;
                 #[inline]
@@ -134,7 +134,7 @@ assert_eq!(size_of::<Option<core::num::", stringify!($Ty), ">>(), size_of::<", s
                 }
             }
 
-            #[stable(feature = "nonzero_bitor", since = "1.43.0")]
+            #[stable(feature = "nonzero_bitor", since = "1.45.0")]
             impl BitOr<$Ty> for $Int {
                 type Output = $Ty;
                 #[inline]
@@ -146,15 +146,15 @@ assert_eq!(size_of::<Option<core::num::", stringify!($Ty), ">>(), size_of::<", s
                 }
             }
 
-            #[stable(feature = "nonzero_bitor", since = "1.43.0")]
+            #[stable(feature = "nonzero_bitor", since = "1.45.0")]
             impl BitOrAssign for $Ty {
                 #[inline]
                 fn bitor_assign(&mut self, rhs: Self) {
                     *self = *self | rhs;
                 }
             }
 
-            #[stable(feature = "nonzero_bitor", since = "1.43.0")]
+            #[stable(feature = "nonzero_bitor", since = "1.45.0")]
             impl BitOrAssign<$Int> for $Ty {
                 #[inline]
                 fn bitor_assign(&mut self, rhs: $Int) {

src/libproc_macro/lib.rs

@@ -351,14 +351,14 @@ impl Span {
 
     /// Creates a new span with the same line/column information as `self` but
     /// that resolves symbols as though it were at `other`.
-    #[stable(feature = "proc_macro_span_resolved_at", since = "1.43.0")]
+    #[stable(feature = "proc_macro_span_resolved_at", since = "1.45.0")]
     pub fn resolved_at(&self, other: Span) -> Span {
         Span(self.0.resolved_at(other.0))
     }
 
     /// Creates a new span with the same name resolution behavior as `self` but
     /// with the line/column information of `other`.
-    #[stable(feature = "proc_macro_span_located_at", since = "1.43.0")]
+    #[stable(feature = "proc_macro_span_located_at", since = "1.45.0")]
     pub fn located_at(&self, other: Span) -> Span {
         other.resolved_at(*self)
     }

src/librustc_codegen_llvm/back/write.rs

@@ -7,7 +7,7 @@ use crate::back::profiling::{
 use crate::base;
 use crate::common;
 use crate::consts;
-use crate::context::{get_reloc_model, is_pie_binary};
+use crate::context::all_outputs_are_pic_executables;
 use crate::llvm::{self, DiagnosticInfo, PassManager, SMDiagnostic};
 use crate::llvm_util;
 use crate::type_::Type;
@@ -25,6 +25,7 @@ use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{self, Lto, OutputType, Passes, Sanitizer, SwitchWithOptPath};
 use rustc_session::Session;
+use rustc_target::spec::RelocModel;
 
 use libc::{c_char, c_int, c_uint, c_void, size_t};
 use std::ffi::CString;
@@ -35,16 +36,6 @@ use std::slice;
 use std::str;
 use std::sync::Arc;
 
-pub const RELOC_MODEL_ARGS: [(&str, llvm::RelocMode); 7] = [
-    ("pic", llvm::RelocMode::PIC),
-    ("static", llvm::RelocMode::Static),
-    ("default", llvm::RelocMode::Default),
-    ("dynamic-no-pic", llvm::RelocMode::DynamicNoPic),
-    ("ropi", llvm::RelocMode::ROPI),
-    ("rwpi", llvm::RelocMode::RWPI),
-    ("ropi-rwpi", llvm::RelocMode::ROPI_RWPI),
-];
-
 pub const CODE_GEN_MODEL_ARGS: &[(&str, llvm::CodeModel)] = &[
     ("small", llvm::CodeModel::Small),
     ("kernel", llvm::CodeModel::Kernel),
@@ -84,19 +75,13 @@ pub fn write_output_file(
     }
 }
 
-pub fn create_informational_target_machine(
-    sess: &Session,
-    find_features: bool,
-) -> &'static mut llvm::TargetMachine {
-    target_machine_factory(sess, config::OptLevel::No, find_features)()
+pub fn create_informational_target_machine(sess: &Session) -> &'static mut llvm::TargetMachine {
+    target_machine_factory(sess, config::OptLevel::No)()
         .unwrap_or_else(|err| llvm_err(sess.diagnostic(), &err).raise())
 }
 
-pub fn create_target_machine(
-    tcx: TyCtxt<'_>,
-    find_features: bool,
-) -> &'static mut llvm::TargetMachine {
-    target_machine_factory(&tcx.sess, tcx.backend_optimization_level(LOCAL_CRATE), find_features)()
+pub fn create_target_machine(tcx: TyCtxt<'_>) -> &'static mut llvm::TargetMachine {
+    target_machine_factory(&tcx.sess, tcx.backend_optimization_level(LOCAL_CRATE))()
         .unwrap_or_else(|err| llvm_err(tcx.sess.diagnostic(), &err).raise())
 }
 
@@ -126,15 +111,22 @@ fn to_pass_builder_opt_level(cfg: config::OptLevel) -> llvm::PassBuilderOptLevel
     }
 }
 
-// If find_features is true this won't access `sess.crate_types` by assuming
-// that `is_pie_binary` is false. When we discover LLVM target features
-// `sess.crate_types` is uninitialized so we cannot access it.
+fn to_llvm_relocation_model(relocation_model: RelocModel) -> llvm::RelocModel {
+    match relocation_model {
+        RelocModel::Static => llvm::RelocModel::Static,
+        RelocModel::Pic => llvm::RelocModel::PIC,
+        RelocModel::DynamicNoPic => llvm::RelocModel::DynamicNoPic,
+        RelocModel::Ropi => llvm::RelocModel::ROPI,
+        RelocModel::Rwpi => llvm::RelocModel::RWPI,
+        RelocModel::RopiRwpi => llvm::RelocModel::ROPI_RWPI,
+    }
+}
+
 pub fn target_machine_factory(
     sess: &Session,
     optlvl: config::OptLevel,
-    find_features: bool,
 ) -> Arc<dyn Fn() -> Result<&'static mut llvm::TargetMachine, String> + Send + Sync> {
-    let reloc_model = get_reloc_model(sess);
+    let reloc_model = to_llvm_relocation_model(sess.relocation_model());
 
     let (opt_level, _) = to_llvm_opt_settings(optlvl);
     let use_softfp = sess.opts.cg.soft_float;
@@ -175,7 +167,7 @@ pub fn target_machine_factory(
     let features = features.join(",");
     let features = CString::new(features).unwrap();
     let abi = SmallCStr::new(&sess.target.target.options.llvm_abiname);
-    let is_pie_binary = !find_features && is_pie_binary(sess);
+    let pic_is_pie = all_outputs_are_pic_executables(sess);
     let trap_unreachable = sess.target.target.options.trap_unreachable;
     let emit_stack_size_section = sess.opts.debugging_opts.emit_stack_sizes;
 
@@ -192,7 +184,7 @@ pub fn target_machine_factory(
                 reloc_model,
                 opt_level,
                 use_softfp,
-                is_pie_binary,
+                pic_is_pie,
                 ffunction_sections,
                 fdata_sections,
                 trap_unreachable,

src/librustc_codegen_llvm/context.rs

@@ -21,7 +21,7 @@ use rustc_session::Session;
 use rustc_span::source_map::{Span, DUMMY_SP};
 use rustc_span::symbol::Symbol;
 use rustc_target::abi::{HasDataLayout, LayoutOf, PointeeInfo, Size, TargetDataLayout, VariantIdx};
-use rustc_target::spec::{HasTargetSpec, Target};
+use rustc_target::spec::{HasTargetSpec, RelocModel, Target};
 
 use std::cell::{Cell, RefCell};
 use std::ffi::CStr;
@@ -87,22 +87,6 @@ pub struct CodegenCx<'ll, 'tcx> {
     local_gen_sym_counter: Cell<usize>,
 }
 
-pub fn get_reloc_model(sess: &Session) -> llvm::RelocMode {
-    let reloc_model_arg = match sess.opts.cg.relocation_model {
-        Some(ref s) => &s[..],
-        None => &sess.target.target.options.relocation_model[..],
-    };
-
-    match crate::back::write::RELOC_MODEL_ARGS.iter().find(|&&arg| arg.0 == reloc_model_arg) {
-        Some(x) => x.1,
-        _ => {
-            sess.err(&format!("{:?} is not a valid relocation mode", reloc_model_arg));
-            sess.abort_if_errors();
-            bug!();
-        }
-    }
-}
-
 fn get_tls_model(sess: &Session) -> llvm::ThreadLocalMode {
     let tls_model_arg = match sess.opts.debugging_opts.tls_model {
         Some(ref s) => &s[..],
@@ -119,12 +103,14 @@ fn get_tls_model(sess: &Session) -> llvm::ThreadLocalMode {
     }
 }
 
-fn is_any_library(sess: &Session) -> bool {
-    sess.crate_types.borrow().iter().any(|ty| *ty != config::CrateType::Executable)
-}
-
-pub fn is_pie_binary(sess: &Session) -> bool {
-    !is_any_library(sess) && get_reloc_model(sess) == llvm::RelocMode::PIC
+/// PIE is potentially more effective than PIC, but can only be used in executables.
+/// If all our outputs are executables, then we can relax PIC to PIE when producing object code.
+/// If the list of crate types is not yet known we conservatively return `false`.
+pub fn all_outputs_are_pic_executables(sess: &Session) -> bool {
+    sess.relocation_model() == RelocModel::Pic
+        && sess.crate_types.try_get().map_or(false, |crate_types| {
+            crate_types.iter().all(|ty| *ty == config::CrateType::Executable)
+        })
 }
 
 fn strip_function_ptr_alignment(data_layout: String) -> String {
@@ -157,7 +143,7 @@ pub unsafe fn create_module(
 
     // Ensure the data-layout values hardcoded remain the defaults.
     if sess.target.target.options.is_builtin {
-        let tm = crate::back::write::create_informational_target_machine(&tcx.sess, false);
+        let tm = crate::back::write::create_informational_target_machine(tcx.sess);
         llvm::LLVMRustSetDataLayoutFromTargetMachine(llmod, tm);
         llvm::LLVMRustDisposeTargetMachine(tm);
 
@@ -200,11 +186,11 @@ pub unsafe fn create_module(
     let llvm_target = SmallCStr::new(&sess.target.target.llvm_target);
     llvm::LLVMRustSetNormalizedTarget(llmod, llvm_target.as_ptr());
 
-    if get_reloc_model(sess) == llvm::RelocMode::PIC {
+    if sess.relocation_model() == RelocModel::Pic {
         llvm::LLVMRustSetModulePICLevel(llmod);
     }
 
-    if is_pie_binary(sess) {
+    if all_outputs_are_pic_executables(sess) {
         llvm::LLVMRustSetModulePIELevel(llmod);
     }
 

src/librustc_codegen_llvm/lib.rs

@@ -110,9 +110,8 @@ impl ExtraBackendMethods for LlvmCodegenBackend {
         &self,
         sess: &Session,
         optlvl: OptLevel,
-        find_features: bool,
     ) -> Arc<dyn Fn() -> Result<&'static mut llvm::TargetMachine, String> + Send + Sync> {
-        back::write::target_machine_factory(sess, optlvl, find_features)
+        back::write::target_machine_factory(sess, optlvl)
     }
     fn target_cpu<'b>(&self, sess: &'b Session) -> &'b str {
         llvm_util::target_cpu(sess)
@@ -201,7 +200,9 @@ impl CodegenBackend for LlvmCodegenBackend {
         match req {
             PrintRequest::RelocationModels => {
                 println!("Available relocation models:");
-                for &(name, _) in back::write::RELOC_MODEL_ARGS.iter() {
+                for name in
+                    &["static", "pic", "dynamic-no-pic", "ropi", "rwpi", "ropi-rwpi", "default"]
+                {
                     println!("    {}", name);
                 }
                 println!();
@@ -351,19 +352,15 @@ impl ModuleLlvm {
         unsafe {
             let llcx = llvm::LLVMRustContextCreate(tcx.sess.fewer_names());
             let llmod_raw = context::create_module(tcx, llcx, mod_name) as *const _;
-            ModuleLlvm { llmod_raw, llcx, tm: create_target_machine(tcx, false) }
+            ModuleLlvm { llmod_raw, llcx, tm: create_target_machine(tcx) }
         }
     }
 
     fn new_metadata(tcx: TyCtxt<'_>, mod_name: &str) -> Self {
         unsafe {
             let llcx = llvm::LLVMRustContextCreate(tcx.sess.fewer_names());
             let llmod_raw = context::create_module(tcx, llcx, mod_name) as *const _;
-            ModuleLlvm {
-                llmod_raw,
-                llcx,
-                tm: create_informational_target_machine(&tcx.sess, false),
-            }
+            ModuleLlvm { llmod_raw, llcx, tm: create_informational_target_machine(tcx.sess) }
         }
     }
 

src/librustc_codegen_llvm/llvm/ffi.rs

@@ -445,8 +445,7 @@ pub struct SanitizerOptions {
 /// LLVMRelocMode
 #[derive(Copy, Clone, PartialEq)]
 #[repr(C)]
-pub enum RelocMode {
-    Default,
+pub enum RelocModel {
     Static,
     PIC,
     DynamicNoPic,
@@ -1946,7 +1945,7 @@ extern "C" {
         Features: *const c_char,
         Abi: *const c_char,
         Model: CodeModel,
-        Reloc: RelocMode,
+        Reloc: RelocModel,
         Level: CodeGenOptLevel,
         UseSoftFP: bool,
         PositionIndependentExecutable: bool,