Merge pull request #49600 from azat/build/rust-lto

RFC: Improve performance of BLAKE3 by 11% by enabling LTO for Rust

CMakeLists.txt

@@ -522,6 +522,26 @@ include (cmake/print_flags.cmake)
 
 if (ENABLE_RUST)
     add_subdirectory (rust)
+
+    # With LTO Rust adds few symbols with global visiblity, the most common is
+    # rust_eh_personality. And this leads to linking errors because multiple
+    # Rust libraries contains the same symbol.
+    #
+    # If it was shared library, that we could use version script for linker to
+    # hide this symbols, but libraries are static.
+    #
+    # we could in theory compile everything to one library but this will be a
+    # mess
+    #
+    # But this should be OK since CI has lots of other builds that are done
+    # without LTO and it will find multiple definitions if there will be any.
+    #
+    # More information about this behaviour in Rust can be found here
+    # - https://github.com/rust-lang/rust/issues/44322
+    # - https://alanwu.space/post/symbol-hygiene/
+    if (ENABLE_THINLTO)
+        set (CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--allow-multiple-definition")
+    endif()
 endif()
 
 add_subdirectory (base)

rust/BLAKE3/Cargo.toml

@@ -11,3 +11,10 @@ libc = "0.2.132"
 [lib]
 crate-type = ["staticlib"]
 
+[profile.release]
+debug = true
+
+[profile.release-thinlto]
+inherits = "release"
+# BLAKE3 module requires "full" LTO (not "thin") to get additional 10% performance benefit
+lto = true

rust/CMakeLists.txt

@@ -34,9 +34,18 @@ function(clickhouse_import_crate)
     else()
         set(CMAKE_CONFIGURATION_TYPES "${CMAKE_BUILD_TYPE};debug")
     endif()
-    # NOTE: we may use LTO for rust too
 
-    corrosion_import_crate(NO_STD ${ARGN})
+    if (CMAKE_BUILD_TYPE_UC STREQUAL "DEBUG")
+        set(profile "")
+    else()
+        if (ENABLE_THINLTO)
+            set(profile "release-thinlto")
+        else()
+            set(profile "release")
+        endif()
+    endif()
+
+    corrosion_import_crate(NO_STD ${ARGN} PROFILE ${profile})
 endfunction()
 
 # Add crate from the build directory.

rust/skim/Cargo.toml

@@ -18,3 +18,8 @@ crate-type = ["staticlib"]
 
 [profile.release]
 debug = true
+
+[profile.release-thinlto]
+inherits = "release"
+# We use LTO here as well to slightly decrease binary size
+lto = true