[PATCH] D125426: Add a new flavor "BBLabels" to LLVM_BUILD_INSTRUMENTED

[Han Shen via Phabricator via llvm-commits]

shenhan created this revision.
shenhan added reviewers: tmsriram, hans.
Herald added a subscriber: mgorny.
Herald added a project: All.
shenhan requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

This CL adds "BBLabels" support for LLVM_BUILD_INSTRUMENTED.

"BBLabels" adds -fbasic-block-sections=labels to C/CXX flags as well as LD flags when doing ThinLTO. With this option, CMAKE builds binaries with auxiliary basic block meta data that later guide propeller[1] profile generation.

With this patch (and its to-be-uploaded child patch that adds support for passing propeller profiles using LLVM_PROFDATA_FILE), it enables people to build propeller optimized llvm tools in a formalized way.

1. Propeller <https://lists.llvm.org/pipermail/llvm-dev/2019-September/135393.html>, submitted in 2021.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D125426

Files:
  llvm/cmake/modules/HandleLLVMOptions.cmake


Index: llvm/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -978,7 +978,7 @@
 option(LLVM_ENABLE_IR_PGO "Build LLVM and tools with IR PGO instrumentation (deprecated)" Off)
 mark_as_advanced(LLVM_ENABLE_IR_PGO)
 
-set(LLVM_BUILD_INSTRUMENTED OFF CACHE STRING "Build LLVM and tools with PGO instrumentation. May be specified as IR or Frontend")
+set(LLVM_BUILD_INSTRUMENTED OFF CACHE STRING "Build LLVM and tools with instrumentation. Use IR, CSIR or Frontend for PGO. Use BBLabels for basic block sections instrumentation")
 set(LLVM_VP_COUNTERS_PER_SITE "1.5" CACHE STRING "Value profile counters to use per site for IR PGO with Clang")
 mark_as_advanced(LLVM_BUILD_INSTRUMENTED LLVM_VP_COUNTERS_PER_SITE)
 string(TOUPPER "${LLVM_BUILD_INSTRUMENTED}" uppercase_LLVM_BUILD_INSTRUMENTED)
@@ -1011,6 +1011,17 @@
         CMAKE_EXE_LINKER_FLAGS
         CMAKE_SHARED_LINKER_FLAGS)
     endif()
+  elseif(uppercase_LLVM_BUILD_INSTRUMENTED STREQUAL "BBLABELS")
+    if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND
+        CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 11)
+      append("-fbasic-block-sections=labels" CMAKE_CXX_FLAGS CMAKE_C_FLAGS)
+    else()
+      message(FATAL_ERROR
+        "LLVM_BUILD_INSTRUMENTED=BBLabels is only available when building with clang")
+    endif()
+    if(uppercase_LLVM_ENABLE_LTO STREQUAL "THIN")
+      append("-Wl,--lto-basic-block-sections=labels" CMAKE_EXE_LINKER_FLAGS)
+    endif()
   else()
     append("-fprofile-instr-generate=\"${LLVM_PROFILE_FILE_PATTERN}\""
       CMAKE_CXX_FLAGS


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D125426.428785.patch
Type: text/x-patch
Size: 1688 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220511/23d4ec62/attachment.bin>