From f3e10a9aee4db798b5ac4a8b5cba9c037dff3faa Mon Sep 17 00:00:00 2001
From: Kalev Lember <klember@redhat.com>
Date: Mon, 19 Dec 2022 13:58:03 +0100
Subject: [PATCH] Revert "Linux: Don't default to ld.gold linker"

Keep on using ld.gold on RHEL 8 and 9 where using ldc with ld.bfd breaks
gtkd and leads to crashing tilix.

https://bugzilla.redhat.com/show_bug.cgi?id=2134875

This reverts commit e125411e988679dfa8cbfc9dcfc05524a37589f7.
---
 driver/linker-gcc.cpp | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/driver/linker-gcc.cpp b/driver/linker-gcc.cpp
index a53936a9aa..5ae90ce650 100644
--- a/driver/linker-gcc.cpp
+++ b/driver/linker-gcc.cpp
@@ -599,12 +599,22 @@ void ArgsBuilder::build(llvm::StringRef outputPath,
 void ArgsBuilder::addLinker() {
   llvm::StringRef linker = opts::linker;
 
-  // Default to ld.bfd for Android (placing .tdata and .tbss sections adjacent
-  // to each other as required by druntime's rt.sections_android, contrary to
-  // gold and lld as of Android NDK r21d).
-  if (global.params.targetTriple->getEnvironment() == llvm::Triple::Android &&
+  // We have a default linker preference for Linux targets. It can be disabled
+  // via `-linker=` (explicitly empty).
+  if (global.params.targetTriple->isOSLinux() &&
       opts::linker.getNumOccurrences() == 0) {
-    linker = "bfd";
+    // Default to ld.bfd for Android (placing .tdata and .tbss sections adjacent
+    // to each other as required by druntime's rt.sections_android, contrary to
+    // gold and lld as of Android NDK r21d).
+    if (global.params.targetTriple->getEnvironment() == llvm::Triple::Android) {
+      linker = "bfd";
+    }
+    // Otherwise default to ld.gold for Linux due to ld.bfd issues with ThinLTO
+    // (see #2278) and older bfd versions stripping llvm.used symbols (e.g.,
+    // ModuleInfo refs) with --gc-sections (see #2870).
+    else {
+      linker = "gold";
+    }
   }
 
   if (!linker.empty())
-- 
2.39.0