[libc-commits] [libc] [libc] Make `crt1.o` available to clang for GPU builds (PR #100599)

[Joseph Huber via libc-commits]

https://github.com/jhuber6 updated https://github.com/llvm/llvm-project/pull/100599

>From 441c12aa99bcb63c03fbbcb952e43b7cdaa55535 Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Thu, 25 Jul 2024 12:01:09 -0500
Subject: [PATCH] [libc] Make `crt1.o` available to clang for GPU builds

Summary:
We want to provide the `crt1.o` object inside of the current build so
that other projects can use it for tests. Because it's currently an
object library (as is also required for the dependencies for the
hermetic tests) this cannot be renamed and is not emitted by default.
Here we simply add an executable that emits bitcode so that CMake will
give it a name.
---
 libc/startup/gpu/CMakeLists.txt | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/libc/startup/gpu/CMakeLists.txt b/libc/startup/gpu/CMakeLists.txt
index 6f67fa9ff44f7..84cbd61b6e51f 100644
--- a/libc/startup/gpu/CMakeLists.txt
+++ b/libc/startup/gpu/CMakeLists.txt
@@ -26,6 +26,16 @@ function(add_startup_object name)
     PROPERTIES
       OUTPUT_NAME ${name}.o
   )
+
+  # Make an executable target of relocatable bitcode for clang if needed.
+  if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR)
+    add_executable(${fq_target_name}.exe $<TARGET_OBJECTS:${fq_target_name}>)
+    set_target_properties(${fq_target_name}.exe PROPERTIES
+      RUNTIME_OUTPUT_DIRECTORY ${LIBC_LIBRARY_DIR}
+      RUNTIME_OUTPUT_NAME ${name}.o)
+    target_link_options(${fq_target_name}.exe PRIVATE 
+                        "-flto" "-Wl,--lto-emit-llvm" "-march= ")
+  endif()
 endfunction()
 
 if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_ARCHITECTURE})
@@ -44,6 +54,7 @@ set(startup_components crt1)
 foreach(target IN LISTS startup_components)
   set(fq_target_name libc.startup.gpu.${target})
   add_dependencies(libc-startup ${fq_target_name})
+
   install(FILES $<TARGET_OBJECTS:${fq_target_name}>
           DESTINATION ${LIBC_INSTALL_LIBRARY_DIR}
           RENAME $<TARGET_PROPERTY:${fq_target_name},OUTPUT_NAME>