Remove more checks for LLVM < 12

compiler/rustc_codegen_llvm/src/abi.rs

@@ -1,7 +1,6 @@
 use crate::builder::Builder;
 use crate::context::CodegenCx;
 use crate::llvm::{self, AttributePlace};
-use crate::llvm_util;
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
@@ -53,15 +52,10 @@ pub trait ArgAttributesExt {
 }
 
 fn should_use_mutable_noalias(cx: &CodegenCx<'_, '_>) -> bool {
-    // LLVM prior to version 12 has known miscompiles in the presence of
-    // noalias attributes (see #54878). Only enable mutable noalias by
-    // default for versions we believe to be safe.
-    cx.tcx
-        .sess
-        .opts
-        .debugging_opts
-        .mutable_noalias
-        .unwrap_or_else(|| llvm_util::get_version() >= (12, 0, 0))
+    // LLVM prior to version 12 had known miscompiles in the presence of
+    // noalias attributes (see #54878), but we don't support earlier
+    // versions at all anymore. We now enable mutable noalias by default.
+    cx.tcx.sess.opts.debugging_opts.mutable_noalias.unwrap_or(true)
 }
 
 impl ArgAttributesExt for ArgAttributes {

compiler/rustc_codegen_llvm/src/builder.rs

@@ -731,7 +731,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     }
 
     fn fptoui_sat(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> Option<&'ll Value> {
-        if llvm_util::get_version() >= (12, 0, 0) && !self.fptoint_sat_broken_in_llvm() {
+        if !self.fptoint_sat_broken_in_llvm() {
             let src_ty = self.cx.val_ty(val);
             let float_width = self.cx.float_width(src_ty);
             let int_width = self.cx.int_width(dest_ty);
@@ -743,7 +743,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     }
 
     fn fptosi_sat(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> Option<&'ll Value> {
-        if llvm_util::get_version() >= (12, 0, 0) && !self.fptoint_sat_broken_in_llvm() {
+        if !self.fptoint_sat_broken_in_llvm() {
             let src_ty = self.cx.val_ty(val);
             let float_width = self.cx.float_width(src_ty);
             let int_width = self.cx.int_width(dest_ty);

compiler/rustc_codegen_llvm/src/context.rs

@@ -134,9 +134,6 @@ pub unsafe fn create_module(
     let llmod = llvm::LLVMModuleCreateWithNameInContext(mod_name.as_ptr(), llcx);
 
     let mut target_data_layout = sess.target.data_layout.clone();
-    if llvm_util::get_version() < (12, 0, 0) && sess.target.arch == "powerpc64" {
-        target_data_layout = target_data_layout.replace("-v256:256:256-v512:512:512", "");
-    }
     if llvm_util::get_version() < (13, 0, 0) {
         if sess.target.arch == "powerpc64" {
             target_data_layout = target_data_layout.replace("-S128", "");

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -406,11 +406,6 @@ pub fn llvm_global_features(sess: &Session) -> Vec<String> {
     // -Ctarget-features
     features.extend(sess.opts.cg.target_feature.split(',').flat_map(&filter));
 
-    // FIXME: Move outline-atomics to target definition when earliest supported LLVM is 12.
-    if get_version() >= (12, 0, 0) && sess.target.llvm_target.contains("aarch64-unknown-linux") {
-        features.push("+outline-atomics".to_string());
-    }
-
     features
 }
 

compiler/rustc_middle/src/ty/layout.rs

@@ -3060,9 +3060,10 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                     // LLVM's definition of `noalias` is based solely on memory
                     // dependencies rather than pointer equality
                     //
-                    // Due to miscompiles in LLVM < 12, we apply a separate NoAliasMutRef attribute
-                    // for UniqueBorrowed arguments, so that the codegen backend can decide
-                    // whether or not to actually emit the attribute.
+                    // Due to past miscompiles in LLVM, we apply a separate NoAliasMutRef attribute
+                    // for UniqueBorrowed arguments, so that the codegen backend can decide whether
+                    // or not to actually emit the attribute. It can also be controlled with the
+                    // `-Zmutable-noalias` debugging option.
                     let no_alias = match kind {
                         PointerKind::Shared | PointerKind::UniqueBorrowed => false,
                         PointerKind::UniqueOwned => true,

compiler/rustc_session/src/options.rs

@@ -1193,7 +1193,7 @@ options! {
     move_size_limit: Option<usize> = (None, parse_opt_number, [TRACKED],
         "the size at which the `large_assignments` lint starts to be emitted"),
     mutable_noalias: Option<bool> = (None, parse_opt_bool, [TRACKED],
-        "emit noalias metadata for mutable references (default: yes for LLVM >= 12, otherwise no)"),
+        "emit noalias metadata for mutable references (default: yes)"),
     new_llvm_pass_manager: Option<bool> = (None, parse_opt_bool, [TRACKED],
         "use new LLVM pass manager (default: no)"),
     nll_facts: bool = (false, parse_bool, [UNTRACKED],

compiler/rustc_target/src/abi/call/mod.rs

@@ -68,8 +68,10 @@ mod attr_impl {
             const NonNull   = 1 << 3;
             const ReadOnly  = 1 << 4;
             const InReg     = 1 << 5;
-            // NoAlias on &mut arguments can only be used with LLVM >= 12 due to miscompiles
-            // in earlier versions. FIXME: Remove this distinction once possible.
+            // Due to past miscompiles in LLVM, we use a separate attribute for
+            // &mut arguments, so that the codegen backend can decide whether
+            // or not to actually emit the attribute. It can also be controlled
+            // with the `-Zmutable-noalias` debugging option.
             const NoAliasMutRef = 1 << 6;
         }
     }

compiler/rustc_target/src/spec/aarch64_be_unknown_linux_gnu.rs

@@ -8,6 +8,7 @@ pub fn target() -> Target {
         data_layout: "E-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128".to_string(),
         arch: "aarch64".to_string(),
         options: TargetOptions {
+            features: "+outline-atomics".to_string(),
             max_atomic_width: Some(128),
             mcount: "\u{1}_mcount".to_string(),
             endian: Endian::Big,

compiler/rustc_target/src/spec/aarch64_be_unknown_linux_gnu_ilp32.rs

@@ -12,6 +12,7 @@ pub fn target() -> Target {
         arch: "aarch64".to_string(),
         options: TargetOptions {
             abi: "ilp32".to_string(),
+            features: "+outline-atomics".to_string(),
             mcount: "\u{1}_mcount".to_string(),
             endian: Endian::Big,
             ..base

compiler/rustc_target/src/spec/aarch64_unknown_linux_gnu.rs

@@ -7,6 +7,7 @@ pub fn target() -> Target {
         data_layout: "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128".to_string(),
         arch: "aarch64".to_string(),
         options: TargetOptions {
+            features: "+outline-atomics".to_string(),
             mcount: "\u{1}_mcount".to_string(),
             max_atomic_width: Some(128),
             supported_sanitizers: SanitizerSet::ADDRESS

compiler/rustc_target/src/spec/aarch64_unknown_linux_gnu_ilp32.rs

@@ -8,6 +8,7 @@ pub fn target() -> Target {
         arch: "aarch64".to_string(),
         options: TargetOptions {
             abi: "ilp32".to_string(),
+            features: "+outline-atomics".to_string(),
             max_atomic_width: Some(128),
             mcount: "\u{1}_mcount".to_string(),
             ..super::linux_gnu_base::opts()

compiler/rustc_target/src/spec/aarch64_unknown_linux_musl.rs

@@ -9,6 +9,10 @@ pub fn target() -> Target {
         pointer_width: 64,
         data_layout: "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128".to_string(),
         arch: "aarch64".to_string(),
-        options: TargetOptions { mcount: "\u{1}_mcount".to_string(), ..base },
+        options: TargetOptions {
+            features: "+outline-atomics".to_string(),
+            mcount: "\u{1}_mcount".to_string(),
+            ..base
+        },
     }
 }