[llvm] [orc-rt] Add ORC_RT_ENABLE_PIC, default on. (PR #221705)

[Lang Hames via llvm-commits]

https://github.com/lhames created https://github.com/llvm/llvm-project/pull/221705

An upcoming patch will add support for building bedrock as a dylib.  In preparation for this, add ORC_RT_ENABLE_PIC option, and use it to set POSITION_INDEPENDENT_CODE (needed for shared library builds) on the bedrock and support object libraries.

>From cd996cdef1282943e3d9cd8441c81ea3a899faf0 Mon Sep 17 00:00:00 2001
From: Lang Hames <lhames at apple.com>
Date: Mon, 7 Sep 2026 21:09:55 +1000
Subject: [PATCH] [orc-rt] Add ORC_RT_ENABLE_PIC, default on.

An upcoming patch will add support for building bedrock as a dylib.  In
preparation for this, add ORC_RT_ENABLE_PIC option, and use it to set
POSITION_INDEPENDENT_CODE (needed for shared library builds) on the
bedrock and support object libraries.
---
 orc-rt/CMakeLists.txt             | 9 +++++++++
 orc-rt/lib/bedrock/CMakeLists.txt | 3 +++
 orc-rt/lib/support/CMakeLists.txt | 3 +++
 3 files changed, 15 insertions(+)

diff --git a/orc-rt/CMakeLists.txt b/orc-rt/CMakeLists.txt
index ad14181eb60a7..01928f1fbc380 100644
--- a/orc-rt/CMakeLists.txt
+++ b/orc-rt/CMakeLists.txt
@@ -57,6 +57,15 @@ option(ORC_RT_ENABLE_ASSERTIONS "Enable assertions independent of build mode." O
 option(ORC_RT_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
 option(ORC_RT_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
 
+option(ORC_RT_ENABLE_PIC "Build position-independent code." ON)
+if(NOT ORC_RT_ENABLE_PIC AND
+   "${CMAKE_C_FLAGS} ${CMAKE_CXX_FLAGS} ${CMAKE_ASM_FLAGS}" MATCHES "-fPIC")
+  message(WARNING
+    "ORC_RT_ENABLE_PIC is OFF, but -fPIC is already in CMAKE_C_FLAGS, "
+    "CMAKE_CXX_FLAGS or CMAKE_ASM_FLAGS, so the build will still be "
+    "position-independent.")
+endif()
+
 # --- Language runtime (RTTI / exceptions) ---
 option(ORC_RT_ENABLE_RTTI "Enable RTTI." ON)
 option(ORC_RT_ENABLE_EXCEPTIONS "Enable exceptions." ON)
diff --git a/orc-rt/lib/bedrock/CMakeLists.txt b/orc-rt/lib/bedrock/CMakeLists.txt
index 63a7a46dcc0da..5174c1644e998 100644
--- a/orc-rt/lib/bedrock/CMakeLists.txt
+++ b/orc-rt/lib/bedrock/CMakeLists.txt
@@ -76,6 +76,9 @@ endif()
 
 add_library(orc-rt-bedrock-objects OBJECT ${ORC_RT_BEDROCK_SOURCES})
 
+set_target_properties(orc-rt-bedrock-objects PROPERTIES
+  POSITION_INDEPENDENT_CODE ${ORC_RT_ENABLE_PIC})
+
 target_link_libraries(orc-rt-bedrock-objects PUBLIC orc-rt-headers)
 
 # Apply RTTI and exceptions compile flags
diff --git a/orc-rt/lib/support/CMakeLists.txt b/orc-rt/lib/support/CMakeLists.txt
index 8d7cb1d5bb5da..e77a1dd268f45 100644
--- a/orc-rt/lib/support/CMakeLists.txt
+++ b/orc-rt/lib/support/CMakeLists.txt
@@ -27,6 +27,9 @@ endif()
 # ship, never shipped on its own.
 add_library(orc-rt-support-objects OBJECT ${ORC_RT_SUPPORT_SOURCES})
 
+set_target_properties(orc-rt-support-objects PROPERTIES
+  POSITION_INDEPENDENT_CODE ${ORC_RT_ENABLE_PIC})
+
 target_link_libraries(orc-rt-support-objects PUBLIC orc-rt-headers)
 
 # Apply RTTI and exceptions compile flags