Auto merge of #113116 - nnethercote:codegen-opts, r=oli-obk

A mish-mash of micro-optimizations

These were aimed at speeding up LLVM codegen, but ended up affecting other places as well.

r? `@bjorn3`

Author: bors

Diff for: compiler/rustc_codegen_cranelift/src/debuginfo/line_info.rs

@@ -81,7 +81,7 @@ impl DebugContext {
 
         match tcx.sess.source_map().lookup_line(span.lo()) {
             Ok(SourceFileAndLine { sf: file, line }) => {
-                let line_pos = file.line_begin_pos(span.lo());
+                let line_pos = file.lines(|lines| lines[line]);
 
                 (
                     file,

Diff for: compiler/rustc_codegen_llvm/src/attributes.rs

@@ -1,7 +1,6 @@
 //! Set and unset common attributes on LLVM values.
 
 use rustc_codegen_ssa::traits::*;
-use rustc_data_structures::small_str::SmallStr;
 use rustc_hir::def_id::DefId;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::ty::{self, TyCtxt};
@@ -481,8 +480,8 @@ pub fn from_fn_attrs<'ll, 'tcx>(
 
     let global_features = cx.tcx.global_backend_features(()).iter().map(|s| s.as_str());
     let function_features = function_features.iter().map(|s| s.as_str());
-    let target_features =
-        global_features.chain(function_features).intersperse(",").collect::<SmallStr<1024>>();
+    let target_features: String =
+        global_features.chain(function_features).intersperse(",").collect();
     if !target_features.is_empty() {
         to_add.push(llvm::CreateAttrStringValue(cx.llcx, "target-features", &target_features));
     }

Diff for: compiler/rustc_codegen_llvm/src/builder.rs

@@ -23,6 +23,7 @@ use rustc_span::Span;
 use rustc_symbol_mangling::typeid::{kcfi_typeid_for_fnabi, typeid_for_fnabi, TypeIdOptions};
 use rustc_target::abi::{self, call::FnAbi, Align, Size, WrappingRange};
 use rustc_target::spec::{HasTargetSpec, SanitizerSet, Target};
+use smallvec::SmallVec;
 use std::borrow::Cow;
 use std::iter;
 use std::ops::Deref;
@@ -225,17 +226,21 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         let args = self.check_call("invoke", llty, llfn, args);
         let funclet_bundle = funclet.map(|funclet| funclet.bundle());
         let funclet_bundle = funclet_bundle.as_ref().map(|b| &*b.raw);
-        let mut bundles = vec![funclet_bundle];
+        let mut bundles: SmallVec<[_; 2]> = SmallVec::new();
+        if let Some(funclet_bundle) = funclet_bundle {
+            bundles.push(funclet_bundle);
+        }
 
         // Emit CFI pointer type membership test
         self.cfi_type_test(fn_attrs, fn_abi, llfn);
 
         // Emit KCFI operand bundle
         let kcfi_bundle = self.kcfi_operand_bundle(fn_attrs, fn_abi, llfn);
         let kcfi_bundle = kcfi_bundle.as_ref().map(|b| &*b.raw);
-        bundles.push(kcfi_bundle);
+        if let Some(kcfi_bundle) = kcfi_bundle {
+            bundles.push(kcfi_bundle);
+        }
 
-        bundles.retain(|bundle| bundle.is_some());
         let invoke = unsafe {
             llvm::LLVMRustBuildInvoke(
                 self.llbuilder,
@@ -1181,17 +1186,21 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         let args = self.check_call("call", llty, llfn, args);
         let funclet_bundle = funclet.map(|funclet| funclet.bundle());
         let funclet_bundle = funclet_bundle.as_ref().map(|b| &*b.raw);
-        let mut bundles = vec![funclet_bundle];
+        let mut bundles: SmallVec<[_; 2]> = SmallVec::new();
+        if let Some(funclet_bundle) = funclet_bundle {
+            bundles.push(funclet_bundle);
+        }
 
         // Emit CFI pointer type membership test
         self.cfi_type_test(fn_attrs, fn_abi, llfn);
 
         // Emit KCFI operand bundle
         let kcfi_bundle = self.kcfi_operand_bundle(fn_attrs, fn_abi, llfn);
         let kcfi_bundle = kcfi_bundle.as_ref().map(|b| &*b.raw);
-        bundles.push(kcfi_bundle);
+        if let Some(kcfi_bundle) = kcfi_bundle {
+            bundles.push(kcfi_bundle);
+        }
 
-        bundles.retain(|bundle| bundle.is_some());
         let call = unsafe {
             llvm::LLVMRustBuildCall(
                 self.llbuilder,

Diff for: compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs

@@ -65,10 +65,10 @@ fn make_mir_scope<'ll, 'tcx>(
         debug_context.scopes[parent]
     } else {
         // The root is the function itself.
-        let loc = cx.lookup_debug_loc(mir.span.lo());
+        let file = cx.sess().source_map().lookup_source_file(mir.span.lo());
         debug_context.scopes[scope] = DebugScope {
-            file_start_pos: loc.file.start_pos,
-            file_end_pos: loc.file.end_pos,
+            file_start_pos: file.start_pos,
+            file_end_pos: file.end_pos,
             ..debug_context.scopes[scope]
         };
         instantiated.insert(scope);

Diff for: compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -262,7 +262,7 @@ impl CodegenCx<'_, '_> {
     pub fn lookup_debug_loc(&self, pos: BytePos) -> DebugLoc {
         let (file, line, col) = match self.sess().source_map().lookup_line(pos) {
             Ok(SourceFileAndLine { sf: file, line }) => {
-                let line_pos = file.line_begin_pos(pos);
+                let line_pos = file.lines(|lines| lines[line]);
 
                 // Use 1-based indexing.
                 let line = (line + 1) as u32;
@@ -331,7 +331,7 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             llvm::LLVMRustDIBuilderCreateSubroutineType(DIB(self), fn_signature)
         };
 
-        let mut name = String::new();
+        let mut name = String::with_capacity(64);
         type_names::push_item_name(tcx, def_id, false, &mut name);
 
         // Find the enclosing function, in case this is a closure.

Diff for: compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs

@@ -28,7 +28,7 @@ pub fn item_namespace<'ll>(cx: &CodegenCx<'ll, '_>, def_id: DefId) -> &'ll DISco
         .map(|parent| item_namespace(cx, DefId { krate: def_id.krate, index: parent }));
 
     let namespace_name_string = {
-        let mut output = String::new();
+        let mut output = String::with_capacity(64);
         type_names::push_item_name(cx.tcx, def_id, false, &mut output);
         output
     };

Diff for: compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1301,7 +1301,7 @@ extern "C" {
         NumArgs: c_uint,
         Then: &'a BasicBlock,
         Catch: &'a BasicBlock,
-        OpBundles: *const Option<&OperandBundleDef<'a>>,
+        OpBundles: *const &OperandBundleDef<'a>,
         NumOpBundles: c_uint,
         Name: *const c_char,
     ) -> &'a Value;
@@ -1673,7 +1673,7 @@ extern "C" {
         Fn: &'a Value,
         Args: *const &'a Value,
         NumArgs: c_uint,
-        OpBundles: *const Option<&OperandBundleDef<'a>>,
+        OpBundles: *const &OperandBundleDef<'a>,
         NumOpBundles: c_uint,
     ) -> &'a Value;
     pub fn LLVMRustBuildMemCpy<'a>(

Diff for: compiler/rustc_data_structures/src/lib.rs

@@ -68,7 +68,6 @@ pub mod macros;
 pub mod obligation_forest;
 pub mod sip128;
 pub mod small_c_str;
-pub mod small_str;
 pub mod snapshot_map;
 pub mod svh;
 pub use ena::snapshot_vec;

Diff for: compiler/rustc_data_structures/src/small_str.rs

@@ -8,13 +8,13 @@ use rustc_middle::ty::TyCtxt;
 
 pub struct Derefer;
 
-pub struct DerefChecker<'tcx> {
+pub struct DerefChecker<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     patcher: MirPatch<'tcx>,
-    local_decls: IndexVec<Local, LocalDecl<'tcx>>,
+    local_decls: &'a IndexVec<Local, LocalDecl<'tcx>>,
 }
 
-impl<'tcx> MutVisitor<'tcx> for DerefChecker<'tcx> {
+impl<'a, 'tcx> MutVisitor<'tcx> for DerefChecker<'a, 'tcx> {
     fn tcx(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
@@ -36,7 +36,7 @@ impl<'tcx> MutVisitor<'tcx> for DerefChecker<'tcx> {
 
             for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() {
                 if !p_ref.projection.is_empty() && p_elem == ProjectionElem::Deref {
-                    let ty = p_ref.ty(&self.local_decls, self.tcx).ty;
+                    let ty = p_ref.ty(self.local_decls, self.tcx).ty;
                     let temp = self.patcher.new_internal_with_info(
                         ty,
                         self.local_decls[p_ref.local].source_info.span,
@@ -70,7 +70,7 @@ impl<'tcx> MutVisitor<'tcx> for DerefChecker<'tcx> {
 
 pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     let patch = MirPatch::new(body);
-    let mut checker = DerefChecker { tcx, patcher: patch, local_decls: body.local_decls.clone() };
+    let mut checker = DerefChecker { tcx, patcher: patch, local_decls: &body.local_decls };
 
     for (bb, data) in body.basic_blocks.as_mut_preserves_cfg().iter_enumerated_mut() {
         checker.visit_basic_block_data(bb, data);

Diff for: compiler/rustc_data_structures/src/small_str/tests.rs

@@ -1072,11 +1072,7 @@ impl SourceMap {
     /// This index is guaranteed to be valid for the lifetime of this `SourceMap`,
     /// since `source_files` is a `MonotonicVec`
     pub fn lookup_source_file_idx(&self, pos: BytePos) -> usize {
-        self.files
-            .borrow()
-            .source_files
-            .binary_search_by_key(&pos, |key| key.start_pos)
-            .unwrap_or_else(|p| p - 1)
+        self.files.borrow().source_files.partition_point(|x| x.start_pos <= pos) - 1
     }
 
     pub fn count_lines(&self) -> usize {