ICE: If-conversion of Conditional Expressions

ICE is a python-based LLVM optimizer currently supporting if-conversion optimization. ICE issimple, modular and a decoupled optimization framework to run LLVM-IR optimization passes. We demonstrate the effectiveness of the tool through the if-conversion optimization. We observe an overall reduction in latency with a modest resource increase. The modular nature of the framework allows users to easily add support for additional optimization passes easily by incrementally supporting the subset of LLVM-IR needed for that particular optimization.

Installation The following softwares need to be installed

1. Python [https://www.python.org/downloads/]
2. pip [https://phoenixnap.com/kb/how-to-install-python-3-windows]
3. numpy [https://docs.scipy.org/doc/numpy/user/install.html]
4. LLVM-tool Chain _ CLANG [https://releases.llvm.org/download.html]
5. PyGraphviz- [https://pygraphviz.github.io/documentation/latest/install.html]
6. Bambu HLS - [https://panda.dei.polimi.it/?page_id=31]

Directory Structure

• src/ - Contains the source code for ICE
  • predicate.py - Contains the base class declaration and core logic for if-conversion
  • CFG.py - Base class definition of CDFG
  • IR.py - Definition of ICE-IR
  • Util,py - Utility functions required for preprocessing data
  • Writer.py - Helper functions for Code generation
  • output/ - The transformed code is output in this directory
• benchmarks/ - Contains the C-code for all the benchmarks tested by ICE
• input_unoptimized/ - Contains the unoptimized version of LLVM-IR extracted from the benchmarks
• output_optimized - Contains the optimized version of LLVM-IR after if-conversion

Usage python predicate.py -h usage: predicate.py [-h] [-fname]

optional arguments: -h, --help show this help message and exit -fname provide the name of the input file [only *.c files]

Sample Usage From the root directory, cd src/ python predicate.py -fname example.c

• The fname argument takes input file name and reads the from the ../benchmarks/ directory and performs if-conversion optimization
• The output is obtained in src/output/ directory
• The output is suffixed with a string '_named'. For example, if the input file name is example.c, the tranformed output will be named as example_transformed.ll
• The transformed LLVM-IR file is fed through Bambu HLS tool with the following command
  • cd src/output/
  • bambu --compiler=I386_CLANG6 example_tranformed.ll --simulate
• The generated Verilog design can be obtained in the same directory