From 98cd818d785f38b59ec874e13e7b83f6521553c7 Mon Sep 17 00:00:00 2001
From: Gary Guo <gary@garyguo.net>
Date: Sun, 10 Apr 2022 02:16:12 +0100
Subject: [PATCH] Refactor exported_symbols and linked_symbols for code reuse

---
 compiler/rustc_codegen_ssa/src/back/linker.rs | 70 +++++++------------
 1 file changed, 26 insertions(+), 44 deletions(-)

diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs
index 044dd9556fed0..fce340232500f 100644
--- a/compiler/rustc_codegen_ssa/src/back/linker.rs
+++ b/compiler/rustc_codegen_ssa/src/back/linker.rs
@@ -12,7 +12,7 @@ use std::{env, mem, str};
 
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
 use rustc_middle::middle::dependency_format::Linkage;
-use rustc_middle::middle::exported_symbols::SymbolExportKind;
+use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo, SymbolExportKind};
 use rustc_middle::ty::TyCtxt;
 use rustc_serialize::{json, Encoder};
 use rustc_session::config::{self, CrateType, DebugInfo, LinkerPluginLto, Lto, OptLevel, Strip};
@@ -1519,22 +1519,13 @@ impl<'a> L4Bender<'a> {
     }
 }
 
-pub(crate) fn exported_symbols(tcx: TyCtxt<'_>, crate_type: CrateType) -> Vec<String> {
-    if let Some(ref exports) = tcx.sess.target.override_export_symbols {
-        return exports.clone();
-    }
-
-    let mut symbols = Vec::new();
-
-    let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
+fn for_each_exported_symbols_include_dep<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    crate_type: CrateType,
+    mut callback: impl FnMut(ExportedSymbol<'tcx>, SymbolExportInfo, CrateNum),
+) {
     for &(symbol, info) in tcx.exported_symbols(LOCAL_CRATE).iter() {
-        if info.level.is_below_threshold(export_threshold) {
-            symbols.push(symbol_export::symbol_name_for_instance_in_crate(
-                tcx,
-                symbol,
-                LOCAL_CRATE,
-            ));
-        }
+        callback(symbol, info, LOCAL_CRATE);
     }
 
     let formats = tcx.dependency_formats(());
@@ -1544,16 +1535,26 @@ pub(crate) fn exported_symbols(tcx: TyCtxt<'_>, crate_type: CrateType) -> Vec<St
         let cnum = CrateNum::new(index + 1);
         // For each dependency that we are linking to statically ...
         if *dep_format == Linkage::Static {
-            // ... we add its symbol list to our export list.
             for &(symbol, info) in tcx.exported_symbols(cnum).iter() {
-                if !info.level.is_below_threshold(export_threshold) {
-                    continue;
-                }
-
-                symbols.push(symbol_export::symbol_name_for_instance_in_crate(tcx, symbol, cnum));
+                callback(symbol, info, cnum);
             }
         }
     }
+}
+
+pub(crate) fn exported_symbols(tcx: TyCtxt<'_>, crate_type: CrateType) -> Vec<String> {
+    if let Some(ref exports) = tcx.sess.target.override_export_symbols {
+        return exports.clone();
+    }
+
+    let mut symbols = Vec::new();
+
+    let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
+    for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
+        if info.level.is_below_threshold(export_threshold) {
+            symbols.push(symbol_export::symbol_name_for_instance_in_crate(tcx, symbol, cnum));
+        }
+    });
 
     symbols
 }
@@ -1572,33 +1573,14 @@ pub(crate) fn linked_symbols(
     let mut symbols = Vec::new();
 
     let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
-    for &(symbol, info) in tcx.exported_symbols(LOCAL_CRATE).iter() {
+    for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
         if info.level.is_below_threshold(export_threshold) || info.used {
             symbols.push((
-                symbol_export::symbol_name_for_instance_in_crate(tcx, symbol, LOCAL_CRATE),
+                symbol_export::symbol_name_for_instance_in_crate(tcx, symbol, cnum),
                 info.kind,
             ));
         }
-    }
-
-    let formats = tcx.dependency_formats(());
-    let deps = formats.iter().find_map(|(t, list)| (*t == crate_type).then_some(list)).unwrap();
-
-    for (index, dep_format) in deps.iter().enumerate() {
-        let cnum = CrateNum::new(index + 1);
-        // For each dependency that we are linking to statically ...
-        if *dep_format == Linkage::Static {
-            // ... we add its symbol list to our export list.
-            for &(symbol, info) in tcx.exported_symbols(cnum).iter() {
-                if info.level.is_below_threshold(export_threshold) || info.used {
-                    symbols.push((
-                        symbol_export::symbol_name_for_instance_in_crate(tcx, symbol, cnum),
-                        info.kind,
-                    ));
-                }
-            }
-        }
-    }
+    });
 
     symbols
 }