[libclc] [libclc] Use a response file when building on Windows (PR #89756)

[Fraser Cormack via cfe-commits]

https://github.com/frasercrmck created https://github.com/llvm/llvm-project/pull/89756

We've recently seen the libclc llvm-link invocations become so long that they exceed the character limits on certain platforms.

Using a 'response file' should solve this by offloading the list of inputs into a separate file, and using special syntax to pass it to llvm-link. Note that neither the response file nor syntax aren't specific to Windows but we restrict it to that platform regardless. We have the option of expanding it to other platforms in the future.

>From 640b18bdf3ccd706a509b534d1b8a01b499eddd7 Mon Sep 17 00:00:00 2001
From: Fraser Cormack <fraser at codeplay.com>
Date: Tue, 23 Apr 2024 13:50:54 +0100
Subject: [PATCH] [libclc] Use a response file when building on Windows

We've recently seen the libclc llvm-link invocations become so long that
they exceed the character limits on certain platforms.

Using a 'response file' should solve this by offloading the list of
inputs into a separate file, and using special syntax to pass it to
llvm-link. Note that neither the response file nor syntax aren't
specific to Windows but we restrict it to that platform regardless. We
have the option of expanding it to other platforms in the future.
---
 libclc/cmake/modules/AddLibclc.cmake | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/libclc/cmake/modules/AddLibclc.cmake b/libclc/cmake/modules/AddLibclc.cmake
index bbedc244a72899..7f4620fa6a21df 100644
--- a/libclc/cmake/modules/AddLibclc.cmake
+++ b/libclc/cmake/modules/AddLibclc.cmake
@@ -88,10 +88,25 @@ function(link_bc)
     ${ARGN}
   )
 
+  set( LINK_INPUT_ARG ${ARG_INPUTS} )
+  if( WIN32 OR CYGWIN )
+    # Create a response file in case the number of inputs exceeds command-line
+    # character limits on certain platforms.
+    file( TO_CMAKE_PATH ${LIBCLC_ARCH_OBJFILE_DIR}/${ARG_TARGET}.rsp RSP_FILE )
+    # Turn it into a space-separate list of input files
+    list( JOIN ARG_INPUTS " " RSP_INPUT )
+    file( WRITE ${RSP_FILE} ${RSP_INPUT} )
+    # Ensure that if this file is removed, we re-run CMake
+    set_property( DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS
+      ${RSP_FILE}
+    )
+    set( LINK_INPUT_ARG "@${RSP_FILE}" )
+  endif()
+
   add_custom_command(
     OUTPUT ${ARG_TARGET}.bc
-    COMMAND libclc::llvm-link -o ${ARG_TARGET}.bc ${ARG_INPUTS}
-    DEPENDS libclc::llvm-link ${ARG_INPUTS}
+    COMMAND libclc::llvm-link -o ${ARG_TARGET}.bc ${LINK_INPUT_ARG}
+    DEPENDS libclc::llvm-link ${ARG_INPUTS} ${RSP_FILE}
   )
 
   add_custom_target( ${ARG_TARGET} ALL DEPENDS ${ARG_TARGET}.bc )