Auto merge of #54911 - ljedrz:cleanup_codegen_llvm_top, r=michaelwoerister

Cleanup top-level codegen_llvm

- improve allocations
- improve common patterns
- remove explicit returns
- fix spelling & grammatical errors
- whitespace & formatting improvements

Author: bors

src/librustc_codegen_llvm/abi.rs

@@ -259,8 +259,7 @@ impl ArgTypeExt<'ll, 'tcx> for ArgType<'tcx, Ty<'tcx>> {
 }
 
 pub trait FnTypeExt<'tcx> {
-    fn of_instance(cx: &CodegenCx<'ll, 'tcx>, instance: &ty::Instance<'tcx>)
-                   -> Self;
+    fn of_instance(cx: &CodegenCx<'ll, 'tcx>, instance: &ty::Instance<'tcx>) -> Self;
     fn new(cx: &CodegenCx<'ll, 'tcx>,
            sig: ty::FnSig<'tcx>,
            extra_args: &[Ty<'tcx>]) -> Self;
@@ -283,8 +282,7 @@ pub trait FnTypeExt<'tcx> {
 }
 
 impl<'tcx> FnTypeExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
-    fn of_instance(cx: &CodegenCx<'ll, 'tcx>, instance: &ty::Instance<'tcx>)
-                       -> Self {
+    fn of_instance(cx: &CodegenCx<'ll, 'tcx>, instance: &ty::Instance<'tcx>) -> Self {
         let fn_ty = instance.ty(cx.tcx);
         let sig = ty_fn_sig(cx, fn_ty);
         let sig = cx.tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
@@ -338,7 +336,7 @@ impl<'tcx> FnTypeExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
             RustIntrinsic | PlatformIntrinsic |
             Rust | RustCall => Conv::C,
 
-            // It's the ABI's job to select this, not us.
+            // It's the ABI's job to select this, not ours.
             System => bug!("system abi should be selected elsewhere"),
 
             Stdcall => Conv::X86Stdcall,
@@ -697,14 +695,13 @@ impl<'tcx> FnTypeExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
             // If the value is a boolean, the range is 0..2 and that ultimately
             // become 0..0 when the type becomes i1, which would be rejected
             // by the LLVM verifier.
-            match scalar.value {
-                layout::Int(..) if !scalar.is_bool() => {
+            if let layout::Int(..) = scalar.value {
+                if !scalar.is_bool() {
                     let range = scalar.valid_range_exclusive(bx.cx);
                     if range.start != range.end {
                         bx.range_metadata(callsite, range);
                     }
                 }
-                _ => {}
             }
         }
         for arg in &self.args {

src/librustc_codegen_llvm/allocator.rs

@@ -33,7 +33,7 @@ pub(crate) unsafe fn codegen(tcx: TyCtxt, mods: &ModuleLlvm, kind: AllocatorKind
     let void = llvm::LLVMVoidTypeInContext(llcx);
 
     for method in ALLOCATOR_METHODS {
-        let mut args = Vec::new();
+        let mut args = Vec::with_capacity(method.inputs.len());
         for ty in method.inputs.iter() {
             match *ty {
                 AllocatorTy::Layout => {

src/librustc_codegen_llvm/attributes.rs

@@ -94,9 +94,8 @@ pub fn set_probestack(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
     // Currently stack probes seem somewhat incompatible with the address
     // sanitizer. With asan we're already protected from stack overflow anyway
     // so we don't really need stack probes regardless.
-    match cx.sess().opts.debugging_opts.sanitizer {
-        Some(Sanitizer::Address) => return,
-        _ => {}
+    if let Some(Sanitizer::Address) = cx.sess().opts.debugging_opts.sanitizer {
+        return
     }
 
     // probestack doesn't play nice either with pgo-gen.
@@ -280,12 +279,14 @@ pub fn provide_extern(providers: &mut Providers) {
         // `NativeLibrary` internally contains information about
         // `#[link(wasm_import_module = "...")]` for example.
         let native_libs = tcx.native_libraries(cnum);
-        let mut def_id_to_native_lib = FxHashMap();
-        for lib in native_libs.iter() {
+
+        let def_id_to_native_lib = native_libs.iter().filter_map(|lib|
             if let Some(id) = lib.foreign_module {
-                def_id_to_native_lib.insert(id, lib);
-            }
+                Some((id, lib))
+            } else {
+                None
             }
+        ).collect::<FxHashMap<_, _>>();
 
         let mut ret = FxHashMap();
         for lib in tcx.foreign_modules(cnum).iter() {
@@ -296,10 +297,10 @@ pub fn provide_extern(providers: &mut Providers) {
                 Some(s) => s,
                 None => continue,
             };
-            for id in lib.foreign_items.iter() {
+            ret.extend(lib.foreign_items.iter().map(|id| {
                 assert_eq!(id.krate, cnum);
-                ret.insert(*id, module.to_string());
-            }
+                (*id, module.to_string())
+            }));
         }
 
         Lrc::new(ret)

src/librustc_codegen_llvm/base.rs

@@ -363,8 +363,8 @@ fn cast_shift_rhs<'ll, F, G>(op: hir::BinOpKind,
         if lhs_sz < rhs_sz {
             trunc(rhs, lhs_llty)
         } else if lhs_sz > rhs_sz {
-            // FIXME (#1877: If shifting by negative
-            // values becomes not undefined then this is wrong.
+            // FIXME (#1877: If in the future shifting by negative
+            // values is no longer undefined then this is wrong.
             zext(rhs, lhs_llty)
         } else {
             rhs
@@ -495,10 +495,8 @@ pub fn codegen_instance<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>, instance: Instance<'
     let sig = common::ty_fn_sig(cx, fn_ty);
     let sig = cx.tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
 
-    let lldecl = match cx.instances.borrow().get(&instance) {
-        Some(&val) => val,
-        None => bug!("Instance `{:?}` not already declared", instance)
-    };
+    let lldecl = cx.instances.borrow().get(&instance).cloned().unwrap_or_else(||
+        bug!("Instance `{:?}` not already declared", instance));
 
     cx.stats.borrow_mut().n_closures += 1;
 
@@ -737,8 +735,8 @@ fn determine_cgu_reuse<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
 pub fn codegen_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                rx: mpsc::Receiver<Box<dyn Any + Send>>)
-                             -> OngoingCodegen {
-
+                               -> OngoingCodegen
+{
     check_for_rustc_errors_attr(tcx);
 
     if let Some(true) = tcx.sess.opts.debugging_opts.thinlto {
@@ -803,8 +801,7 @@ pub fn codegen_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
     // Run the monomorphization collector and partition the collected items into
     // codegen units.
-    let codegen_units =
-        tcx.collect_and_partition_mono_items(LOCAL_CRATE).1;
+    let codegen_units = tcx.collect_and_partition_mono_items(LOCAL_CRATE).1;
     let codegen_units = (*codegen_units).clone();
 
     // Force all codegen_unit queries so they are already either red or green
@@ -837,12 +834,7 @@ pub fn codegen_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         .iter()
         .any(|(_, list)| {
             use rustc::middle::dependency_format::Linkage;
-            list.iter().any(|linkage| {
-                match linkage {
-                    Linkage::Dynamic => true,
-                    _ => false,
-                }
-            })
+            list.iter().any(|&linkage| linkage == Linkage::Dynamic)
         });
     let allocator_module = if any_dynamic_crate {
         None
@@ -1123,7 +1115,15 @@ impl CrateInfo {
             info.load_wasm_imports(tcx, LOCAL_CRATE);
         }
 
-        for &cnum in tcx.crates().iter() {
+        let crates = tcx.crates();
+
+        let n_crates = crates.len();
+        info.native_libraries.reserve(n_crates);
+        info.crate_name.reserve(n_crates);
+        info.used_crate_source.reserve(n_crates);
+        info.missing_lang_items.reserve(n_crates);
+
+        for &cnum in crates.iter() {
             info.native_libraries.insert(cnum, tcx.native_libraries(cnum));
             info.crate_name.insert(cnum, tcx.crate_name(cnum).to_string());
             info.used_crate_source.insert(cnum, tcx.used_crate_source(cnum));
@@ -1165,11 +1165,12 @@ impl CrateInfo {
     }
 
     fn load_wasm_imports(&mut self, tcx: TyCtxt, cnum: CrateNum) {
-        for (&id, module) in tcx.wasm_import_module_map(cnum).iter() {
+        self.wasm_imports.extend(tcx.wasm_import_module_map(cnum).iter().map(|(&id, module)| {
             let instance = Instance::mono(tcx, id);
             let import_name = tcx.symbol_name(instance);
-            self.wasm_imports.insert(import_name.to_string(), module.clone());
-        }
+
+            (import_name.to_string(), module.clone())
+        }));
     }
 }
 

src/librustc_codegen_llvm/builder.rs

@@ -1194,7 +1194,7 @@ impl Builder<'a, 'll, 'tcx> {
             })
             .collect();
 
-        return Cow::Owned(casted_args);
+        Cow::Owned(casted_args)
     }
 
     pub fn lifetime_start(&self, ptr: &'ll Value, size: Size) {

src/librustc_codegen_llvm/common.rs

@@ -336,16 +336,13 @@ pub fn langcall(tcx: TyCtxt,
                 msg: &str,
                 li: LangItem)
                 -> DefId {
-    match tcx.lang_items().require(li) {
-        Ok(id) => id,
-        Err(s) => {
+    tcx.lang_items().require(li).unwrap_or_else(|s| {
         let msg = format!("{} {}", msg, s);
         match span {
             Some(span) => tcx.sess.span_fatal(span, &msg[..]),
             None => tcx.sess.fatal(&msg[..]),
         }
-        }
-    }
+    })
 }
 
 // To avoid UB from LLVM, these two functions mask RHS with an

src/librustc_codegen_llvm/consts.rs

@@ -249,15 +249,14 @@ fn check_and_apply_linkage(
         // extern "C" fn() from being non-null, so we can't just declare a
         // static and call it a day. Some linkages (like weak) will make it such
         // that the static actually has a null value.
-        let llty2 = match ty.sty {
-            ty::RawPtr(ref mt) => cx.layout_of(mt.ty).llvm_type(cx),
-            _ => {
-                if span.is_some() {
-                    cx.sess().span_fatal(span.unwrap(), "must have type `*const T` or `*mut T`")
+        let llty2 = if let ty::RawPtr(ref mt) = ty.sty {
+            cx.layout_of(mt.ty).llvm_type(cx)
+        } else {
+            if let Some(span) = span {
+                cx.sess().span_fatal(span, "must have type `*const T` or `*mut T`")
             } else {
                 bug!("must have type `*const T` or `*mut T`")
             }
-            }
         };
         unsafe {
             // Declare a symbol `foo` with the desired linkage.
@@ -273,9 +272,9 @@ fn check_and_apply_linkage(
             let mut real_name = "_rust_extern_with_linkage_".to_string();
             real_name.push_str(&sym);
             let g2 = declare::define_global(cx, &real_name, llty).unwrap_or_else(||{
-                if span.is_some() {
+                if let Some(span) = span {
                     cx.sess().span_fatal(
-                        span.unwrap(),
+                        span,
                         &format!("symbol `{}` is already defined", &sym)
                     )
                 } else {

src/librustc_codegen_llvm/context.rs

@@ -59,8 +59,8 @@ pub struct CodegenCx<'a, 'tcx: 'a> {
     /// Cache instances of monomorphic and polymorphic items
     pub instances: RefCell<FxHashMap<Instance<'tcx>, &'a Value>>,
     /// Cache generated vtables
-    pub vtables: RefCell<FxHashMap<(Ty<'tcx>,
-                                Option<ty::PolyExistentialTraitRef<'tcx>>), &'a Value>>,
+    pub vtables: RefCell<FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>),
+                                   &'a Value>>,
     /// Cache of constant strings,
     pub const_cstr_cache: RefCell<FxHashMap<LocalInternedString, &'a Value>>,
 
@@ -318,10 +318,8 @@ impl<'b, 'tcx> CodegenCx<'b, 'tcx> {
         if let Some(v) = self.intrinsics.borrow().get(key).cloned() {
             return v;
         }
-        match declare_intrinsic(self, key) {
-            Some(v) => return v,
-            None => bug!("unknown intrinsic '{}'", key)
-        }
+
+        declare_intrinsic(self, key).unwrap_or_else(|| bug!("unknown intrinsic '{}'", key))
     }
 
     /// Generate a new symbol name with the given prefix. This symbol name must
@@ -465,9 +463,10 @@ impl LayoutOf for &'a CodegenCx<'ll, 'tcx> {
 
     fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout {
         self.tcx.layout_of(ty::ParamEnv::reveal_all().and(ty))
-            .unwrap_or_else(|e| match e {
-                LayoutError::SizeOverflow(_) => self.sess().fatal(&e.to_string()),
-                _ => bug!("failed to get layout for `{}`: {}", ty, e)
+            .unwrap_or_else(|e| if let LayoutError::SizeOverflow(_) = e {
+                self.sess().fatal(&e.to_string())
+            } else {
+                bug!("failed to get layout for `{}`: {}", ty, e)
             })
     }
 }
@@ -772,5 +771,6 @@ fn declare_intrinsic(cx: &CodegenCx<'ll, '_>, key: &str) -> Option<&'ll Value> {
         ifn!("llvm.dbg.declare", fn(Type::metadata(cx), Type::metadata(cx)) -> void);
         ifn!("llvm.dbg.value", fn(Type::metadata(cx), t_i64, Type::metadata(cx)) -> void);
     }
-    return None;
+
+    None
 }