From 5eed82c2bb7d1236d6b0bcb8fe1b6dc220284df1 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 14 May 2026 21:18:10 +0000
Subject: [PATCH] Enable linker dead code elimination for apphost, dotnet, and
 nethost

Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>
---
 eng/native/functions.cmake                     | 18 ++++++++++++++++++
 .../corehost/apphost/standalone/CMakeLists.txt |  1 +
 src/native/corehost/dotnet/CMakeLists.txt      |  1 +
 src/native/corehost/nethost/CMakeLists.txt     |  2 ++
 4 files changed, 22 insertions(+)

diff --git a/eng/native/functions.cmake b/eng/native/functions.cmake
index f7066de09a764c..52459476d143d7 100644
--- a/eng/native/functions.cmake
+++ b/eng/native/functions.cmake
@@ -655,6 +655,24 @@ function(link_natvis_sources_for_target targetName linkKind)
     endforeach()
 endfunction()
 
+# Enable linker dead code elimination for the given target in CHECKED/RELEASE/RELWITHDEBINFO
+function(enable_dead_code_elimination targetName)
+  set(dce_configs "$<OR:$<CONFIG:Checked>,$<CONFIG:Release>,$<CONFIG:RelWithDebInfo>>")
+
+  if (MSVC)
+    target_link_options(${targetName} PRIVATE $<${dce_configs}:/OPT:REF>)
+    return()
+  endif()
+
+  target_compile_options(${targetName} PRIVATE $<${dce_configs}:-fdata-sections>)
+
+  if (CLR_CMAKE_HOST_APPLE)
+    target_link_options(${targetName} PRIVATE $<${dce_configs}:LINKER:-dead_strip>)
+  else()
+    target_link_options(${targetName} PRIVATE $<${dce_configs}:LINKER:--gc-sections>)
+  endif()
+endfunction()
+
 # Add sanitizer runtime support code to the target.
 function(add_sanitizer_runtime_support targetName)
   # Add sanitizer support functions.
diff --git a/src/native/corehost/apphost/standalone/CMakeLists.txt b/src/native/corehost/apphost/standalone/CMakeLists.txt
index 17b114fd0c373c..0f3e1ecc7a32ee 100644
--- a/src/native/corehost/apphost/standalone/CMakeLists.txt
+++ b/src/native/corehost/apphost/standalone/CMakeLists.txt
@@ -34,6 +34,7 @@ add_executable(apphost ${SOURCES} ${RESOURCES})
 target_link_libraries(apphost PRIVATE hostmisc fxr_resolver)
 
 add_sanitizer_runtime_support(apphost)
+enable_dead_code_elimination(apphost)
 
 if(NOT CLR_CMAKE_TARGET_WIN32)
     disable_pax_mprotect(apphost)
diff --git a/src/native/corehost/dotnet/CMakeLists.txt b/src/native/corehost/dotnet/CMakeLists.txt
index 5704c911ac9568..2aa3052967be8e 100644
--- a/src/native/corehost/dotnet/CMakeLists.txt
+++ b/src/native/corehost/dotnet/CMakeLists.txt
@@ -17,6 +17,7 @@ add_executable(dotnet ${SOURCES})
 target_link_libraries(dotnet PRIVATE hostmisc fxr_resolver)
 
 add_sanitizer_runtime_support(dotnet)
+enable_dead_code_elimination(dotnet)
 
 if(NOT CLR_CMAKE_TARGET_WIN32)
     disable_pax_mprotect(dotnet)
diff --git a/src/native/corehost/nethost/CMakeLists.txt b/src/native/corehost/nethost/CMakeLists.txt
index 83c6f4aac8e3ec..b10dac5492b37d 100644
--- a/src/native/corehost/nethost/CMakeLists.txt
+++ b/src/native/corehost/nethost/CMakeLists.txt
@@ -38,6 +38,8 @@ target_link_libraries(libnethost PRIVATE hostmisc::public fxr_resolver)
 target_compile_definitions(nethost PRIVATE FEATURE_LIBHOST NETHOST_EXPORT)
 target_compile_definitions(libnethost PRIVATE FEATURE_LIBHOST NETHOST_EXPORT)
 
+enable_dead_code_elimination(nethost)
+
 set_target_properties(nethost PROPERTIES MACOSX_RPATH TRUE)
 set_target_properties(libnethost PROPERTIES MACOSX_RPATH TRUE)
 set_target_properties(libnethost PROPERTIES PREFIX "")