Merge pull request #2360 from gottesmm/lto-changes-for-upstream

Lto changes for upstream

Author: gottesmm

CMakeLists.txt

@@ -301,7 +301,10 @@ else()
 endif()
 
 # lipo is used to create universal binaries.
-find_program(LIPO "lipo")
+if("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
+  include(SwiftDarwin)
+  find_toolchain_tool(LIPO "${SWIFT_DARWIN_XCRUN_TOOLCHAIN}" lipo)
+endif()
 
 if("${SWIFT_NATIVE_LLVM_TOOLS_PATH}" STREQUAL "")
   set(SWIFT_CROSS_COMPILING FALSE)

cmake/modules/SwiftDarwin.cmake

@@ -11,3 +11,10 @@ function(get_default_toolchain_dir result_var_name)
   set("${result_var_name}" "${toolchain_dir}" PARENT_SCOPE)
 endfunction()
 
+function(find_toolchain_tool result_var_name toolchain tool)
+  execute_process(
+      COMMAND "xcrun" "--toolchain" "${toolchain}" "--find" "${tool}"
+      OUTPUT_VARIABLE tool_path
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+  set("${result_var_name}" "${tool_path}" PARENT_SCOPE)
+endfunction()

utils/build-script-impl

@@ -277,10 +277,15 @@ function float_min() {
 function num_llvm_parallel_lto_link_jobs() {
     case "$(uname -s -m)" in
         Darwin\ x86_64)
-            # Currently with -gline-tables-only clang is ~3.5GB on Darwin. Use
-            # the formula GB Memory/3.5GB to get the number of parallel link
-            # threads we can support.
-            local NUM_MEMORY_THREADS=$(echo $(system_memory_in_bytes)/1000000000.0/3.5 | bc)
+            # *WARNING! HUERISTIC!*
+            #
+            # Use the formula (GB Memory - 3)/6.0GB to get the number of
+            # parallel link threads we can support. This gives the OS 3 GB of
+            # room to work with.
+            #
+            # This is a bit conservative, but I have found that this number
+            # prevents me from swapping on my test machine.
+            local NUM_MEMORY_THREADS=$(echo \( $(system_memory_in_bytes)/1000000000.0 - 3.0 \) / 6.0 | bc)
             echo $(float_min "${NUM_MEMORY_THREADS}" "${BUILD_JOBS}")
             ;;
         *)
@@ -293,10 +298,15 @@ function num_llvm_parallel_lto_link_jobs() {
 function num_swift_parallel_lto_link_jobs() {
     case "$(uname -s -m)" in
         Darwin\ x86_64)
-            # Currently with -gline-tables-only swift is ~5-6GB on Darwin. Use
-            # the formula GB Memory/6GB to get the number of parallel link
-            # threads we can support.
-            local NUM_MEMORY_THREADS=$(echo $(system_memory_in_bytes)/1000000000/6.0 | bc)
+            # *WARNING! HUERISTIC!*
+            #
+            # Use the formula (GB Memory - 3)/8.0GB to get the number of
+            # parallel link threads we can support. This gives the OS 3 GB of
+            # room to work with.
+            #
+            # This is a bit conservative, but I have found that this number
+            # prevents me from swapping on my test machine.
+            local NUM_MEMORY_THREADS=$(echo \( $(system_memory_in_bytes)/1000000000 - 3.0 \) / 8.0 | bc)
             echo $(float_min "${NUM_MEMORY_THREADS}" "${BUILD_JOBS}")
             ;;
         *)
@@ -531,10 +541,6 @@ function set_deployment_target_based_options() {
                 fi
 
                 llvm_cmake_options+=(
-                    "-DCMAKE_C_FLAGS=-O2 -flto -gline-tables-only -fno-stack-protector "
-                    "-DCMAKE_CXX_FLAGS=-O2 -flto -gline-tables-only -fno-stack-protector "
-                    "-DCMAKE_C_FLAGS_RELWITHDEBINFO=-O2 -flto -gline-tables-only -fno-stack-protector "
-                    "-DCMAKE_CXX_FLAGS_RELWITHDEBINFO=-O2 -flto -gline-tables-only -fno-stack-protector "
                     "-DLLVM_PARALLEL_LINK_JOBS=$(num_llvm_parallel_lto_link_jobs)"
                 )
             fi
@@ -1239,6 +1245,9 @@ function llvm_c_flags() {
     if [[ $(is_cmake_release_build_type "${LLVM_BUILD_TYPE}") ]] ; then
         echo -n " -fno-stack-protector"
     fi
+    if [[ $(true_false "${LLVM_ENABLE_LTO}") ]] ; then
+        echo -n " -gline-tables-only"
+    fi
 }
 
 function cmark_c_flags() {
@@ -1527,6 +1536,7 @@ for deployment_target in "${HOST_TARGET}" "${CROSS_TOOLS_DEPLOYMENT_TARGETS[@]}"
                     -DLLVM_TARGETS_TO_BUILD="${LLVM_TARGETS_TO_BUILD}"
                     -DLLVM_INCLUDE_TESTS:BOOL=$(true_false "${SOURCE_TREE_INCLUDES_TESTS}")
                     -DLLVM_INCLUDE_DOCS:BOOL=TRUE
+                    -DLLVM_ENABLE_LTO=$(true_false "${LLVM_ENABLE_LTO}")
                     "${llvm_cmake_options[@]}"
                 )
                 if [[ $(is_cross_tools_deployment_target ${deployment_target}) ]] ; then
@@ -1619,6 +1629,7 @@ for deployment_target in "${HOST_TARGET}" "${CROSS_TOOLS_DEPLOYMENT_TARGETS[@]}"
                     -DCMAKE_CXX_FLAGS="$(swift_c_flags ${deployment_target})"
                     -DCMAKE_BUILD_TYPE:STRING="${SWIFT_BUILD_TYPE}"
                     -DLLVM_ENABLE_ASSERTIONS:BOOL=$(true_false "${SWIFT_ENABLE_ASSERTIONS}")
+                    -DLLVM_ENABLE_LTO=$(true_false "${LLVM_ENABLE_LTO}")
                     -DSWIFT_ANALYZE_CODE_COVERAGE:STRING=$(toupper "${SWIFT_ANALYZE_CODE_COVERAGE}")
                     -DSWIFT_STDLIB_BUILD_TYPE:STRING="${SWIFT_STDLIB_BUILD_TYPE}"
                     -DSWIFT_STDLIB_ASSERTIONS:BOOL=$(true_false "${SWIFT_STDLIB_ENABLE_ASSERTIONS}")