Don't deduplicate anonymous allocations

Author: bjorn3

Cargo.lock

@@ -9,11 +9,11 @@ crate-type = ["dylib"]
 
 [dependencies]
 # These have to be in sync with each other
-cranelift-codegen = { git = "https://github.com/bytecodealliance/wasmtime/", branch = "main", features = ["unwind", "x64"] }
-cranelift-frontend = { git = "https://github.com/bytecodealliance/wasmtime/", branch = "main" }
-cranelift-module = { git = "https://github.com/bytecodealliance/wasmtime/", branch = "main" }
-cranelift-jit = { git = "https://github.com/bytecodealliance/wasmtime/", branch = "main", optional = true }
-cranelift-object = { git = "https://github.com/bytecodealliance/wasmtime/", branch = "main" }
+cranelift-codegen = { git = "https://github.com/bjorn3/wasmtime.git", branch = "anon_allocs", features = ["unwind", "x64"] }
+cranelift-frontend = { git = "https://github.com/bjorn3/wasmtime.git", branch = "anon_allocs" }
+cranelift-module = { git = "https://github.com/bjorn3/wasmtime.git", branch = "anon_allocs" }
+cranelift-jit = { git = "https://github.com/bjorn3/wasmtime.git", branch = "anon_allocs", optional = true }
+cranelift-object = { git = "https://github.com/bjorn3/wasmtime.git", branch = "anon_allocs" }
 target-lexicon = "0.11.0"
 gimli = { version = "0.23.0", default-features = false, features = ["write"]}
 object = { version = "0.23.0", default-features = false, features = ["std", "read_core", "write", "archive", "coff", "elf", "macho", "pe"] }

Cargo.toml

@@ -296,6 +296,11 @@ fn main() {
     unsafe {
         global_asm_test();
     }
+
+    // Both statics have a reference that points to the same anonymous allocation.
+    static REF1: &u8 = &42;
+    static REF2: &u8 = REF1;
+    assert_eq!(*REF1, *REF2);
 }
 
 #[cfg(all(not(jit), target_os = "linux"))]

example/mini_core_hello_world.rs

@@ -47,6 +47,7 @@ rm src/test/ui/issues/issue-51947.rs # same
 rm src/test/ui/numbers-arithmetic/saturating-float-casts.rs # intrinsic gives different but valid result
 rm src/test/ui/mir/mir_misc_casts.rs # depends on deduplication of constants
 rm src/test/ui/mir/mir_raw_fat_ptr.rs # same
+rm src/test/ui/consts/issue-33537.rs # same
 rm src/test/ui/async-await/async-fn-size-moved-locals.rs # -Cpanic=abort shrinks some generator by one byte
 rm src/test/ui/async-await/async-fn-size-uninit-locals.rs # same
 rm src/test/ui/generator/size-moved-locals.rs # same

scripts/test_rustc_tests.sh

@@ -6,6 +6,7 @@ use rustc_middle::ty::adjustment::PointerCast;
 use rustc_middle::ty::layout::FnAbiExt;
 use rustc_target::abi::call::FnAbi;
 
+use crate::constant::ConstantCx;
 use crate::prelude::*;
 
 pub(crate) fn codegen_fn<'tcx>(cx: &mut crate::CodegenCx<'_, 'tcx>, instance: Instance<'tcx>) {
@@ -47,6 +48,7 @@ pub(crate) fn codegen_fn<'tcx>(cx: &mut crate::CodegenCx<'_, 'tcx>, instance: In
         tcx,
         pointer_type,
         vtables: FxHashMap::default(),
+        constants_cx: ConstantCx::new(),
 
         instance,
         symbol_name,
@@ -92,6 +94,8 @@ pub(crate) fn codegen_fn<'tcx>(cx: &mut crate::CodegenCx<'_, 'tcx>, instance: In
     let source_info_set = fx.source_info_set;
     let local_map = fx.local_map;
 
+    fx.constants_cx.finalize(fx.tcx, &mut *fx.cx.module);
+
     // Store function in context
     let context = &mut cx.cached_context;
     context.func = func;

src/base.rs

@@ -4,6 +4,7 @@ use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::{Integer, Primitive};
 use rustc_target::spec::{HasTargetSpec, Target};
 
+use crate::constant::ConstantCx;
 use crate::prelude::*;
 
 pub(crate) fn pointer_ty(tcx: TyCtxt<'_>) -> types::Type {
@@ -232,6 +233,7 @@ pub(crate) struct FunctionCx<'m, 'clif, 'tcx> {
     pub(crate) tcx: TyCtxt<'tcx>,
     pub(crate) pointer_type: Type, // Cached from module
     pub(crate) vtables: FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), DataId>,
+    pub(crate) constants_cx: ConstantCx,
 
     pub(crate) instance: Instance<'tcx>,
     pub(crate) symbol_name: SymbolName<'tcx>,

src/common.rs

@@ -2,7 +2,7 @@
 
 use rustc_span::DUMMY_SP;
 
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_errors::ErrorReported;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::interpret::{
@@ -13,12 +13,12 @@ use rustc_middle::ty::ConstKind;
 use cranelift_codegen::ir::GlobalValueData;
 use cranelift_module::*;
 
-use crate::prelude::*;
+use crate::{prelude::*, CodegenCx};
 
-#[derive(Default)]
 pub(crate) struct ConstantCx {
     todo: Vec<TodoItem>,
     done: FxHashSet<DataId>,
+    anon_allocs: FxHashMap<AllocId, DataId>,
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -28,6 +28,10 @@ enum TodoItem {
 }
 
 impl ConstantCx {
+    pub(crate) fn new() -> Self {
+        ConstantCx { todo: vec![], done: FxHashSet::default(), anon_allocs: FxHashMap::default() }
+    }
+
     pub(crate) fn finalize(mut self, tcx: TyCtxt<'_>, module: &mut dyn Module) {
         //println!("todo {:?}", self.todo);
         define_all_allocs(tcx, module, &mut self);
@@ -74,8 +78,10 @@ pub(crate) fn check_constants(fx: &mut FunctionCx<'_, '_, '_>) -> bool {
     all_constants_ok
 }
 
-pub(crate) fn codegen_static(constants_cx: &mut ConstantCx, def_id: DefId) {
+pub(crate) fn codegen_static(cx: &mut CodegenCx<'_, '_>, def_id: DefId) {
+    let mut constants_cx = ConstantCx::new();
     constants_cx.todo.push(TodoItem::Static(def_id));
+    constants_cx.finalize(cx.tcx, &mut *cx.module);
 }
 
 pub(crate) fn codegen_tls_ref<'tcx>(
@@ -182,9 +188,13 @@ pub(crate) fn codegen_const_value<'tcx>(
                     let alloc_kind = fx.tcx.get_global_alloc(ptr.alloc_id);
                     let base_addr = match alloc_kind {
                         Some(GlobalAlloc::Memory(alloc)) => {
-                            fx.cx.constants_cx.todo.push(TodoItem::Alloc(ptr.alloc_id));
-                            let data_id =
-                                data_id_for_alloc_id(fx.cx.module, ptr.alloc_id, alloc.mutability);
+                            fx.constants_cx.todo.push(TodoItem::Alloc(ptr.alloc_id));
+                            let data_id = data_id_for_alloc_id(
+                                &mut fx.constants_cx,
+                                fx.cx.module,
+                                ptr.alloc_id,
+                                alloc.mutability,
+                            );
                             let local_data_id =
                                 fx.cx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
                             if fx.clif_comments.enabled() {
@@ -243,8 +253,9 @@ fn pointer_for_allocation<'tcx>(
     alloc: &'tcx Allocation,
 ) -> crate::pointer::Pointer {
     let alloc_id = fx.tcx.create_memory_alloc(alloc);
-    fx.cx.constants_cx.todo.push(TodoItem::Alloc(alloc_id));
-    let data_id = data_id_for_alloc_id(fx.cx.module, alloc_id, alloc.mutability);
+    fx.constants_cx.todo.push(TodoItem::Alloc(alloc_id));
+    let data_id =
+        data_id_for_alloc_id(&mut fx.constants_cx, &mut *fx.cx.module, alloc_id, alloc.mutability);
 
     let local_data_id = fx.cx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
     if fx.clif_comments.enabled() {
@@ -255,18 +266,14 @@ fn pointer_for_allocation<'tcx>(
 }
 
 fn data_id_for_alloc_id(
+    cx: &mut ConstantCx,
     module: &mut dyn Module,
     alloc_id: AllocId,
     mutability: rustc_hir::Mutability,
 ) -> DataId {
-    module
-        .declare_data(
-            &format!(".L__alloc_{:x}", alloc_id.0),
-            Linkage::Local,
-            mutability == rustc_hir::Mutability::Mut,
-            false,
-        )
-        .unwrap()
+    *cx.anon_allocs.entry(alloc_id).or_insert_with(|| {
+        module.declare_anonymous_data(mutability == rustc_hir::Mutability::Mut, false).unwrap()
+    })
 }
 
 fn data_id_for_static(
@@ -344,7 +351,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
                     GlobalAlloc::Memory(alloc) => alloc,
                     GlobalAlloc::Function(_) | GlobalAlloc::Static(_) => unreachable!(),
                 };
-                let data_id = data_id_for_alloc_id(module, alloc_id, alloc.mutability);
+                let data_id = data_id_for_alloc_id(cx, module, alloc_id, alloc.mutability);
                 (data_id, alloc, None)
             }
             TodoItem::Static(def_id) => {
@@ -397,7 +404,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
                 }
                 GlobalAlloc::Memory(target_alloc) => {
                     cx.todo.push(TodoItem::Alloc(reloc));
-                    data_id_for_alloc_id(module, reloc, target_alloc.mutability)
+                    data_id_for_alloc_id(cx, module, reloc, target_alloc.mutability)
                 }
                 GlobalAlloc::Static(def_id) => {
                     if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
@@ -419,8 +426,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
             data_ctx.write_data_addr(offset.bytes() as u32, global_value, addend as i64);
         }
 
-        // FIXME don't duplicate definitions in lazy jit mode
-        let _ = module.define_data(data_id, &data_ctx);
+        module.define_data(data_id, &data_ctx).unwrap();
         cx.done.insert(data_id);
     }
 

src/constant.rs

@@ -121,9 +121,7 @@ fn module_codegen(
             MonoItem::Fn(inst) => {
                 cx.tcx.sess.time("codegen fn", || crate::base::codegen_fn(&mut cx, inst));
             }
-            MonoItem::Static(def_id) => {
-                crate::constant::codegen_static(&mut cx.constants_cx, def_id)
-            }
+            MonoItem::Static(def_id) => crate::constant::codegen_static(&mut cx, def_id),
             MonoItem::GlobalAsm(item_id) => {
                 let item = cx.tcx.hir().item(item_id);
                 if let rustc_hir::ItemKind::GlobalAsm(rustc_hir::GlobalAsm { asm }) = item.kind {

src/driver/aot.rs

@@ -58,7 +58,7 @@ pub(super) fn run_jit(tcx: TyCtxt<'_>, backend_config: BackendConfig) -> ! {
                     CodegenMode::JitLazy => codegen_shim(&mut cx, inst),
                 },
                 MonoItem::Static(def_id) => {
-                    crate::constant::codegen_static(&mut cx.constants_cx, def_id);
+                    crate::constant::codegen_static(&mut cx, def_id);
                 }
                 MonoItem::GlobalAsm(item_id) => {
                     let item = cx.tcx.hir().item(item_id);

src/driver/jit.rs

@@ -36,7 +36,6 @@ use rustc_session::Session;
 use cranelift_codegen::settings::{self, Configurable};
 
 pub use crate::config::*;
-use crate::constant::ConstantCx;
 use crate::prelude::*;
 
 mod abi;
@@ -123,7 +122,6 @@ struct CodegenCx<'m, 'tcx: 'm> {
     tcx: TyCtxt<'tcx>,
     module: &'m mut dyn Module,
     global_asm: String,
-    constants_cx: ConstantCx,
     cached_context: Context,
     debug_context: Option<DebugContext<'tcx>>,
     unwind_context: UnwindContext<'tcx>,
@@ -147,15 +145,13 @@ impl<'m, 'tcx> CodegenCx<'m, 'tcx> {
             tcx,
             module,
             global_asm: String::new(),
-            constants_cx: ConstantCx::default(),
             cached_context: Context::new(),
             debug_context,
             unwind_context,
         }
     }
 
     fn finalize(self) -> (String, Option<DebugContext<'tcx>>, UnwindContext<'tcx>) {
-        self.constants_cx.finalize(self.tcx, self.module);
         (self.global_asm, self.debug_context, self.unwind_context)
     }
 }