[Take 2:] Make opt-viewer more usable by general developers - part 1/N

[OfekShilon]

Summary

This is a renewed attempt to submit opt-viewer improvements, originally started at https://reviews.llvm.org/D131518.
Part 1/N is just an addition of an example 1-file cpp project with a build script and a run_optview.sh script.
The current submission includes most of @fhahn comments (clang-format, llvm license header,etc.).

The only request knowingly not addressed yet is to make the small utility script ./opt-viewer/cpp_optimization_example/run_optview.sh create a virtual-env and install dependencies. I'm not sure if this would make it cleaner or dirtier... I think I personally would have been surprised by such side effects for a run of a script which was supposed to just render htmls. Opinions are very welcome.

[fhahn]

Looks good, but can add a short readme showing how to use it, e.g. what paths need to be specified/set to use the correct clang and so on?

[fhahn]

reverse ping, any updates? :)

[justincady]

I recently watched the CppCon talk on this and subsequently found this diff. So, another reverse ping: any update here? :)

llvm/tools/opt-viewer/CMakeLists.txt

 set (files
   "opt-diff.py"
   "opt-stats.py"
   "opt-viewer.py"
   "optpmap.py"
   "optrecord.py"
-  "style.css")
+  "style.css"
+  "requirements.txt"
+  "cpp_optimization_example/main.cc"
+  "cpp_optimization_example/Makefile"
+  "cpp_optimization_example/run_optview.sh")
 
 foreach (file ${files})
   install(PROGRAMS ${file}
     DESTINATION "${CMAKE_INSTALL_DATADIR}/opt-viewer"
     COMPONENT opt-viewer)
 endforeach (file)
 
 add_custom_target(opt-viewer DEPENDS ${files})
 if(NOT LLVM_ENABLE_IDE)
   add_llvm_install_targets("install-opt-viewer"
                            DEPENDS opt-viewer
                            COMPONENT opt-viewer)
 endif()

llvm/tools/opt-viewer/cpp_optimization_example/.gitignore

+example
+*.o
+yaml_optimization_remarks
+.depend
+.vscode
+html_output

llvm/tools/opt-viewer/cpp_optimization_example/Makefile

+CC=clang++
+CXX=clang++
+RM=rm -f
+MKDIR_P=mkdir -p
+OBJS_DIR=objs
+DEPENDS_FILE=${OBJS_DIR}/.depend
+YAML_OUTPUT_DIR=yaml_optimization_remarks
+OPTIMIZATION_RECORD_FLAGS=-fsave-optimization-record -foptimization-record-file=./${YAML_OUTPUT_DIR}/$(patsubst %.o,%.opt.yaml,$(notdir $@))
+CPPFLAGS=-O3 -std=c++17
+LDFLAGS=
+LDLIBS=
+BINARY_NAME=example
+
+SRCS=$(wildcard *.cpp)
+OBJS=$(addprefix $(OBJS_DIR)/,$(subst .cpp,.o,$(SRCS)))
+
+.PHONY: output_folder
+
+all: output_folder ${BINARY_NAME}
+
+directories: ${YAML_OUTPUT_DIR} ${OBJS_DIR}
+
+${YAML_OUTPUT_DIR} ${OBJS_DIR}:
+  ${MKDIR_P} $@
+
+${BINARY_NAME}: $(OBJS)
+  $(CXX) $(LDFLAGS) -o $(BINARY_NAME) $(OBJS) $(LDLIBS)
+
+${OBJS_DIR}/%.o : %.cpp
+  $(CXX) -c $(CFLAGS) $(CPPFLAGS) $(OPTIMIZATION_RECORD_FLAGS) $< -o $@
+
+depend: $(DEPENDS_FILE)
+
+$(DEPENDS_FILE): $(SRCS)
+  $(RM) $(DEPENDS_FILE)
+  $(MKDIR_P) ${YAML_OUTPUT_DIR} ${OBJS_DIR}
+  $(CXX) $(CPPFLAGS) -MM $^ >> $(DEPENDS_FILE)
+
+include $(DEPENDS_FILE)
+
+clean:
+  $(RM) -r ${YAML_OUTPUT_DIR} ${OBJS_DIR}
+

llvm/tools/opt-viewer/cpp_optimization_example/main.cpp

+//===-- main.cpp ------------------------------------------------*- C++-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===---------------------------------------------------------------------===//
+//
+// Source for a toy cpp project, demonstrating opt-viewer usage.
+//
+//===---------------------------------------------------------------------===//
+
+#include <iostream>
+#include <vector>
+
+// Based on Roi Barkan - "Argument passing, core guidelines and concepts" -
+// https://www.youtube.com/watch?v=uylFACqcWYI
+void scale_down(std::vector<double> &v, const double &a) {
+  for (auto &item : v) {
+    item /= a;
+  }
+}
+
+void scale_down_example() {
+  std::vector<double> v{2, 1, 2, 3, 4};
+  scale_down(v, v[0]);
+}
+
+int main() {
+  scale_down_example();
+  return 0;
+}

llvm/tools/opt-viewer/cpp_optimization_example/run_optview.sh

+#!/bin/bash
+set -euo pipefail
+cd "$(dirname "$0")" || exit 1
+
+echo "Running make..."
+make
+
+echo "Running opt-viewer..."
+../opt-viewer.py --open-browser --output-dir ./html_output --source-dir ./ ./yaml_optimization_remarks