[llvm] 904f1b1 - [CMake] Configure ccache using command line options (#134857)

[via llvm-commits]

Author: Kajetan Puchalski
Date: 2025-04-14T20:25:07+01:00
New Revision: 904f1b17d30335b102bd05f63a73e9ed5576ba0a

URL: https://github.com/llvm/llvm-project/commit/904f1b17d30335b102bd05f63a73e9ed5576ba0a
DIFF: https://github.com/llvm/llvm-project/commit/904f1b17d30335b102bd05f63a73e9ed5576ba0a.diff

LOG: [CMake] Configure ccache using command line options (#134857)

Since ccache 4.8, it is possible to pass configuration options directly
to ccache on the command line as opposed to through environment
variables.
This is the intended way for CMake to configure ccache, as described on
the GitHub wiki for the project:
https://github.com/ccache/ccache/wiki/CMake

This should allow for uniform ccache configuration that does not rely on
platform-specific environment setup.

Rework the way ccache is configured by LLVM accordingly.

---------

Signed-off-by: Kajetan Puchalski <kajetan.puchalski at arm.com>

Added: 
    

Modified: 
    llvm/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index cfd1a086c0fc2..6913fde73be67 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -271,30 +271,51 @@ set(LLVM_CCACHE_BUILD OFF CACHE BOOL "Set to ON for a ccache enabled build")
 if(LLVM_CCACHE_BUILD)
   find_program(CCACHE_PROGRAM ccache)
   if(CCACHE_PROGRAM)
+    # ccache --version example output: "ccache version 4.9.1\n(..)"
+    execute_process(COMMAND ${CCACHE_PROGRAM} --version OUTPUT_VARIABLE CCACHE_VERSION_STR)
+    string(REGEX MATCH "[0-9]+\.[0-9]+\.?[0-9]*" CCACHE_VERSION "${CCACHE_VERSION_STR}")
+
     set(LLVM_CCACHE_MAXSIZE "" CACHE STRING "Size of ccache")
     set(LLVM_CCACHE_DIR "" CACHE STRING "Directory to keep ccached data")
-    set(LLVM_CCACHE_PARAMS "CCACHE_CPP2=yes CCACHE_HASHDIR=yes"
-        CACHE STRING "Parameters to pass through to ccache")
 
-    if(NOT CMAKE_SYSTEM_NAME MATCHES "Windows")
-      set(CCACHE_PROGRAM "${LLVM_CCACHE_PARAMS} ${CCACHE_PROGRAM}")
+    # ccache only supports passing options on the command line from version 4.8.0
+    # use a workaround with ad-hoc environment variables for older versions
+    if (CCACHE_VERSION VERSION_LESS "4.8.0")
+      set(LLVM_CCACHE_PARAMS "CCACHE_CPP2=yes;CCACHE_HASHDIR=yes"
+          CACHE STRING "Parameters to pass through to ccache")
+
+      if(NOT CMAKE_SYSTEM_NAME MATCHES "Windows")
+        set(launcher_params ${LLVM_CCACHE_PARAMS})
+        if (LLVM_CCACHE_MAXSIZE)
+          set(launcher_params CCACHE_MAXSIZE=${LLVM_CCACHE_MAXSIZE} ${launcher_params})
+        endif()
+        if (LLVM_CCACHE_DIR)
+          set(launcher_params CCACHE_DIR=${LLVM_CCACHE_DIR} ${launcher_params})
+        endif()
+        set(launcher ${launcher_params} "${CCACHE_PROGRAM}")
+      else()
+        if(LLVM_CCACHE_MAXSIZE OR LLVM_CCACHE_DIR OR
+           NOT LLVM_CCACHE_PARAMS MATCHES "CCACHE_CPP2=yes;CCACHE_HASHDIR=yes")
+          message(FATAL_ERROR "Ccache configuration through CMake is not supported on Windows. Please use environment variables.")
+        endif()
+        set(launcher "${CCACHE_PROGRAM}")
+      endif()
+    else()
+      set(LLVM_CCACHE_PARAMS "run_second_cpp=true;hash_dir=true"
+          CACHE STRING "Parameters to pass through to ccache")
+
+      set(launcher_params ${LLVM_CCACHE_PARAMS})
       if (LLVM_CCACHE_MAXSIZE)
-        set(CCACHE_PROGRAM "CCACHE_MAXSIZE=${LLVM_CCACHE_MAXSIZE} ${CCACHE_PROGRAM}")
+        set(launcher_params max_size=${LLVM_CCACHE_MAXSIZE} ${launcher_params})
       endif()
       if (LLVM_CCACHE_DIR)
-        set(CCACHE_PROGRAM "CCACHE_DIR=${LLVM_CCACHE_DIR} ${CCACHE_PROGRAM}")
+        set(launcher_params cache_dir=${LLVM_CCACHE_DIR} ${launcher_params})
       endif()
-      set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ${CCACHE_PROGRAM})
-    else()
-      if(LLVM_CCACHE_MAXSIZE OR LLVM_CCACHE_DIR OR
-         NOT LLVM_CCACHE_PARAMS MATCHES "CCACHE_CPP2=yes CCACHE_HASHDIR=yes")
-        message(FATAL_ERROR "Ccache configuration through CMake is not supported on Windows. Please use environment variables.")
-      endif()
-      # RULE_LAUNCH_COMPILE should work with Ninja but currently has issues
-      # with cmd.exe and some MSVC tools other than cl.exe
-      set(CMAKE_C_COMPILER_LAUNCHER ${CCACHE_PROGRAM})
-      set(CMAKE_CXX_COMPILER_LAUNCHER ${CCACHE_PROGRAM})
+      set(launcher "${CCACHE_PROGRAM}" ${launcher_params})
     endif()
+
+    set(CMAKE_C_COMPILER_LAUNCHER ${launcher})
+    set(CMAKE_CXX_COMPILER_LAUNCHER ${launcher})
   else()
     message(FATAL_ERROR "Unable to find the program ccache. Set LLVM_CCACHE_BUILD to OFF")
   endif()