Exploring Automatic ifunc and Gimple Intermediate Representation in GCC (Project Stage 2 - Part 1)

Introduction

In the world of compilers and optimization, understanding the intermediate representation of code is crucial. This blog post delves into the investigation of the proof-of-concept Automatic ifunc tool and the Gimple intermediate representation produced by the GCC compiler. We'll explore the steps involved, analyze the outputs, and discuss my key findings while working on this project.

Part I: Automatic ifunc Tool Exploration

Step 1: Obtaining the Proof-of-Concept Code

The journey begins by obtaining the autoifunc proof-of-concept code from the specified file and unpacking it on an aarch64 machine. The provided commands guide the user through this process, resulting in a directory structure at ~/spo600/autoifunc-preprocessor-poc/.

cd
tar xvf /public/spo600-autoifunc-preprocessor-pos.tgz
cd spo600/autoifunc-preprocessor-poc/

Step 2: Building and Comparing Outputs

The "make" command is used to build the assembly language code. The subsequent diff command compares the outputs of 'function.c' and 'function_ifunc.c'. 

make
diff function.c function_ifunc.c

This step helps identify the resolver function, two copies of 'adjust_channels', pragma statements, and the indirect function prototype, shedding light on the differences introduced by the automatic ifunc tool.

Step 3: Generating Gimple Representation

The compiler option '-fdump-tree-gimple' is added to the compilation process. This generates additional output files with the '.gimple' extension. 

make CFLAGS=-fdump-tree-gimple

Gimple is the intermediate representation used by GCC, providing a tree-based view of the program.

Step 4: Analyzing Gimple Files

Differences between SVE and ASIMD Versions
The Gimple files for 'function_ifunc.c' are examined for any disparities between the SVE and ASIMD versions of the function. This step uncovers insights into how the compiler handles different architectures.

Autovectorization
The investigation checks if autovectorization has been applied to the code at this stage in the compilation process. This involves identifying vectorization-related Gimple statements, showcasing the compiler's optimization capabilities.

Reflection of #pragma Lines
The examination includes understanding how #pragma lines in the source file are reflected in the Gimple representation. This highlights the translation of high-level directives into the intermediate representation.

Step 5: Transforming Gimple Representation

The final step explores what's required to transform the Gimple representation of function.c into that of 'function_ifunc.c'. This involves a meticulous analysis of differences, updating the source code based on Gimple statements, and ensuring proper application of pragma directives.

Conclusion

This journey into the Automatic ifunc tool and Gimple intermediate representation offers a glimpse into the intricacies of compiler optimization. Understanding the transformations applied to the code at different stages provides developers with insights to write more efficient and optimized programs. The investigation showcased in this blog post serves as a foundation for further exploration into compiler internals and code optimization strategies.

Stay tuned to my blogs for more adventures in the realm of compilers and programming optimization as we delve into part 2 of the Project stage 2 working on the designing part!

Comments

Post a Comment

Popular posts from this blog

Navigating the Patch Submission Processes in Open Source Communities: Linux Kernel & Python

     In the open-source world, contributing to established projects like the Linux kernel or the Python programming language can be a rewarding experience. However, the journey from having a great idea to getting your code accepted can be quite different from one community to another. In this blog post, I'll try to introduce and explain the patch submission process in two prominent open-source communities – Linux and Python – while highlighting the advantages and disadvantages of each approach. Linux Kernel: The Linux Patch Submission Process: Development : Like most open-source projects, contributors begin by developing their code changes. Version Control : Developers work in their own branches, forking the Linux kernel repository in Git. Patch Submission : Patches are submitted through the Linux kernel's mailing list as plain text email messages. Mailing List : The "linux-kernel" mailing list is the primary channel
Read more

Building GCC from Source: A Journey into Compiler Construction (Project Stage 1)

Introduction: Building a compiler from source code is an informative yet intricate process that provides insights into the heart of programming languages and system architectures. In this blog post, I'll share my experience building the GNU Compiler Collection (GCC) on both an x86_64 system and an AArch64 system, highlighting the steps, time considerations, the impact of parallel building, and ultimately, how I confirmed the functionality of the newly built compiler. Building on x86_64 System: Step 1: Cloning the GCC Repository The journey began by cloning the GCC repository from the official Git repository: git clone git://gcc.gnu.org/git/gcc.git Step 2: Creating a Build Directory To maintain a clean separation between the source and build files, I created a dedicated build directory outside the source tree: mkdir build_x86_64 cd build_x86_64 Step 3: Configuring t
Read more

Lab 3 - Understanding arithmetic/math and strings in 6502 assembly language(SPO600)

Introduction As a beginner delving into the world of assembly language programming, I recently had the opportunity to explore the realms of the 6502 Jumps, Branches, and Procedural Math (including Bitwise Operations). In Lab 3, I got the learning opportunity to work with 6502 Math and String in order to develop and understand how we can utilize user interaction to receive our desired output. My quest led me to a captivating code adventure - a color selector with live updates. This blog chronicles my journey, highlighting the code's working functionality, critical elements, and my reflections on the experience. The Actual Code Block The code begins with a warm welcome, invoking the SCINIT routine to initialize and clear the screen, setting the stage for the colorful escapade. A delightful list of color names is then printed, each ready to be chosen by the user.   ; Colour selector - live updates ; ROM routine entry points define                    SCINIT              
Read more