Rollup merge of #81618 - bjorn3:sync_cg_clif-2021-02-01, r=bjorn3

[rust.git] / src / backend.rs

diff --git a/src/backend.rs b/src/backend.rs
index 0d654aed160ca2f68835180c05eb80d5dc194f76..0ce34c904bdcc43d274263f46035c5302d5b5a78 100644 (file)
--- a/src/backend.rs
+++ b/src/backend.rs
@@ -1,14 +1,16 @@
+//! Abstraction around the object writing crate
+
 use std::convert::{TryFrom, TryInto};
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_session::Session;
 
-use cranelift_module::{FuncId, Module};
+use cranelift_module::FuncId;
 
 use object::write::*;
 use object::{RelocationEncoding, RelocationKind, SectionKind, SymbolFlags};
 
-use cranelift_object::{ObjectBackend, ObjectBuilder, ObjectProduct};
+use cranelift_object::{ObjectBuilder, ObjectModule, ObjectProduct};
 
 use gimli::SectionId;
 
@@ -68,8 +70,19 @@ fn add_debug_section(
         .into_bytes();
 
         let segment = self.object.segment_name(StandardSegment::Debug).to_vec();
-        let section_id = self.object.add_section(segment, name, SectionKind::Debug);
-        self.object.section_mut(section_id).set_data(data, 1);
+        // FIXME use SHT_X86_64_UNWIND for .eh_frame
+        let section_id = self.object.add_section(
+            segment,
+            name,
+            if id == SectionId::EhFrame {
+                SectionKind::ReadOnlyData
+            } else {
+                SectionKind::Debug
+            },
+        );
+        self.object
+            .section_mut(section_id)
+            .set_data(data, if id == SectionId::EhFrame { 8 } else { 1 });
         let symbol_id = self.object.section_symbol(section_id);
         (section_id, symbol_id)
     }
@@ -95,7 +108,7 @@ fn add_debug_reloc(
                 Relocation {
                     offset: u64::from(reloc.offset),
                     symbol,
-                    kind: RelocationKind::Absolute,
+                    kind: reloc.kind,
                     encoding: RelocationEncoding::Generic,
                     size: reloc.size * 8,
                     addend: i64::try_from(symbol_offset).unwrap() + reloc.addend,
@@ -119,10 +132,16 @@ fn add_constructor(&mut self, func_id: FuncId) {
         let init_array_section =
             self.object
                 .add_section(segment.to_vec(), b".init_array".to_vec(), SectionKind::Data);
+        let address_size = self
+            .object
+            .architecture()
+            .address_size()
+            .expect("address_size must be known")
+            .bytes();
         self.object.append_section_data(
             init_array_section,
             &std::iter::repeat(0)
-                .take(8 /*FIXME pointer size*/)
+                .take(address_size.into())
                 .collect::<Vec<u8>>(),
             8,
         );
@@ -131,7 +150,7 @@ fn add_constructor(&mut self, func_id: FuncId) {
                 init_array_section,
                 object::write::Relocation {
                     offset: 0,
-                    size: 64, // FIXME pointer size
+                    size: address_size * 8,
                     kind: RelocationKind::Absolute,
                     encoding: RelocationEncoding::Generic,
                     symbol,
@@ -142,30 +161,17 @@ fn add_constructor(&mut self, func_id: FuncId) {
     }
 }
 
-pub(crate) trait Emit {
-    fn emit(self) -> Vec<u8>;
-}
-
-impl Emit for ObjectProduct {
-    fn emit(self) -> Vec<u8> {
-        self.object.write().unwrap()
-    }
-}
-
 pub(crate) fn with_object(sess: &Session, name: &str, f: impl FnOnce(&mut Object)) -> Vec<u8> {
-    let triple = crate::build_isa(sess, true).triple().clone();
+    let triple = crate::build_isa(sess).triple().clone();
 
     let binary_format = match triple.binary_format {
         target_lexicon::BinaryFormat::Elf => object::BinaryFormat::Elf,
         target_lexicon::BinaryFormat::Coff => object::BinaryFormat::Coff,
         target_lexicon::BinaryFormat::Macho => object::BinaryFormat::MachO,
-        target_lexicon::BinaryFormat::Wasm => sess.fatal("binary format wasm is unsupported"),
-        target_lexicon::BinaryFormat::Unknown => sess.fatal("binary format is unknown"),
+        binary_format => sess.fatal(&format!("binary format {} is unsupported", binary_format)),
     };
     let architecture = match triple.architecture {
-        target_lexicon::Architecture::I386
-        | target_lexicon::Architecture::I586
-        | target_lexicon::Architecture::I686 => object::Architecture::I386,
+        target_lexicon::Architecture::X86_32(_) => object::Architecture::I386,
         target_lexicon::Architecture::X86_64 => object::Architecture::X86_64,
         target_lexicon::Architecture::Arm(_) => object::Architecture::Arm,
         target_lexicon::Architecture::Aarch64(_) => object::Architecture::Aarch64,
@@ -185,17 +191,16 @@ pub(crate) fn with_object(sess: &Session, name: &str, f: impl FnOnce(&mut Object
     metadata_object.write().unwrap()
 }
 
-pub(crate) type Backend =
-    impl cranelift_module::Backend<Product: AddConstructor + Emit + WriteDebugInfo>;
-
-pub(crate) fn make_module(sess: &Session, name: String) -> Module<Backend> {
-    let module: Module<ObjectBackend> = Module::new(
-        ObjectBuilder::new(
-            crate::build_isa(sess, true),
-            name + ".o",
-            cranelift_module::default_libcall_names(),
-        )
-        .unwrap(),
-    );
-    module
+pub(crate) fn make_module(sess: &Session, name: String) -> ObjectModule {
+    let mut builder = ObjectBuilder::new(
+        crate::build_isa(sess),
+        name + ".o",
+        cranelift_module::default_libcall_names(),
+    )
+    .unwrap();
+    // Unlike cg_llvm, cg_clif defaults to disabling -Zfunction-sections. For cg_llvm binary size
+    // is important, while cg_clif cares more about compilation times. Enabling -Zfunction-sections
+    // can easily double the amount of time necessary to perform linking.
+    builder.per_function_section(sess.opts.debugging_opts.function_sections.unwrap_or(false));
+    ObjectModule::new(builder)
 }