cconvey commented on code in PR #11189:
URL: https://github.com/apache/tvm/pull/11189#discussion_r864952809
##########
CMakeLists.txt:
##########
@@ -509,6 +510,103 @@ set(LIBINFO_FILE
${CMAKE_CURRENT_LIST_DIR}/src/support/libinfo.cc)
add_lib_info(${LIBINFO_FILE})
list(REMOVE_ITEM COMPILER_SRCS ${LIBINFO_FILE})
+# Caches the build.
+# Note that ccache-3.x doesn't support nvcc well, so CUDA kernels may never
hit the cache and still
+# need to be re-compiled every time. Using ccache 4.0+ can resolve this issue.
+#
+# NOTE: CMAKE_C[XX]_COMPILER_LAUNCHER only affects build targets that we add
*later*.
+# So we want this logic to appear towards the top of thet this CMakeLists.txt
file.
+if(USE_CCACHE) # True for AUTO, ON, /path/to/ccache
+
+
#-------------------------------------------------------------------------------------------------
+ # Determine which requested policy.
+ # If ccache is required but can't be found, fail with an error message.
+
#-------------------------------------------------------------------------------------------------
+ if("${USE_CCACHE}" STREQUAL "AUTO") # Auto mode
+ set(CCACHE_PROGRAM_CANDIDATE ccache)
+ set(CCACHE_REQUIRED FALSE)
+ elseif("${USE_CCACHE}" MATCHES ${IS_TRUE_PATTERN})
+ set(CCACHE_PROGRAM_CANDIDATE ccache)
+ set(CCACHE_REQUIRED TRUE)
+ else() # /path/to/ccache
+ set(CCACHE_PROGRAM_CANDIDATE "${USE_CCACHE}")
+ set(CCACHE_REQUIRED TRUE)
+ endif()
+
+ find_program(CCACHE_PROGRAM "${CCACHE_PROGRAM_CANDIDATE}")
+ if (CCACHE_PROGRAM)
+ message(STATUS "Found ccache program: '${CCACHE_PROGRAM}'")
+ else()
+ # Note: Once we require cmake >= 3.18, we can simplify this logic using
+ # `find_program(... REQUIRED)`.
+ if (CCACHE_REQUIRED)
+ message(FATAL_ERROR "Unable to find ccache program:
'${CCACHE_PROGRAM_CANDIDATE}'")
+ else()
+ message(STATUS "Unable to find ccache program:
'${CCACHE_PROGRAM_CANDIDATE}'")
Review Comment:
Good question. I think the basic issue is that we can't distinguish the two
causes of `USE_CCACHE=AUTO`:
- the user explicitly set it that way, vs.
- the user left the default value in place, perhaps unwittingly.
If we knew that the user explicitly set it to `AUTO`, I think `WARNING` is a
better choice than `STATUS`.
Since we don't know either way, my personal preference is to bias towards
clean builds.
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