// Halide tutorial lesson 3: Inspecting the generated code
// Halide入门第3讲：检查llvm编译生成的代码
// This lesson demonstrates how to inspect what the Halide compiler is producing.
// 本课演示了怎样查看Halide编译器做了些什么
// On linux, you can compile and run it like so:
// linux操作系统，按如下操作编译和运行
// g++ lesson_03*.cpp -g -I ../include -L ../bin -lHalide -lpthread -ldl -o lesson_03 -std=c++11
// LD_LIBRARY_PATH=../bin ./lesson_03
// On os x:
// g++ lesson_03*.cpp -g -I ../include -L ../bin -lHalide -o lesson_03 -std=c++11
// DYLD_LIBRARY_PATH=../bin ./lesson_03
// If you have the entire Halide source tree, you can also build it by
// running:
// make tutorial_lesson_03_debugging_1
// in a shell with the current directory at the top of the halide
// source tree.
#include "Halide.h"
#include <stdio.h>
// This time we'll just import the entire Halide namespace
using namespace Halide;
int main(int argc, char **argv) {
// We'll start by defining the simple single-stage imaging
// pipeline from lesson 1.
// This lesson will be about debugging, but unfortunately in C++,
// objects don't know their own names, which makes it hard for us
// to understand the generated code. To get around this, you can
// pass a string to the Func and Var constructors to give them a
// name for debugging purposes.
// 本课主要陈述调试（debugging），但c++中的对象并没有自己的名字标签，这就给理解生成代码增加了困难
// 为了克服这个问题，你可以给Func和Var的构造函数传入一个string类型的名字，从而达到方便调试的目的
Func gradient("gradient");
Var x("x"), y("y");
gradient(x, y) = x + y;
// Realize the function to produce an output image. We'll keep it
// very small for this lesson.
Buffer<int> output = gradient.realize(8, 8);
// That line compiled and ran the pipeline. Try running this
// lesson with the environment variable HL_DEBUG_CODEGEN set to
// 1. It will print out the various stages of compilation, and a
// pseudocode representation of the final pipeline.
// 设置环境变量HL_DEBUG_CODEGEN=1，此时运行程序会打印出编译的不同阶段和最终pipeline的伪代码
// export HL_DEBUG_CODEGEN=1
// If you set HL_DEBUG_CODEGEN to a higher number, you can see
// more and more details of how Halide compiles your pipeline.
// Setting HL_DEBUG_CODEGEN=2 shows the Halide code at each stage
// of compilation, and also the llvm bitcode we generate at the
// end.
// 设置HL_DEBUG_CODEGEN=2，此时会输出Halide编译的各个不同阶段，而且会输出llvm
//（开源编译器基础框架）最终生成的字节码
// export HL_DEBUG_CODEGEN=2
// Halide will also output an HTML version of this output, which
// supports syntax highlighting and code-folding, so it can be
// nicer to read for large pipelines. Open gradient.html with your
// browser after running this tutorial.
// Halide也提供HTML形式的伪代码输出，支持语法高亮，代码折叠，翻遍大规模复杂pipeline的阅读
gradient.compile_to_lowered_stmt("gradient.html", {}, HTML);
// You can usually figure out what code Halide is generating using
// this pseudocode. In the next lesson we'll see how to snoop on
// Halide at runtime.
printf("Success!\n");
return 0;
}
1. 设置环境变量HL_DEBUG_CODEGEN=1/2，jit即时编译打印出中间编译结果，方便调试
2. Func.compile_to_lowered_stmt("gradient.html", {}, HTML)， 将Halide中间调度以html形式保存出来，方便阅读和理解中间调度过程