Using llvm-mca to Analyze and Optimize C++ Code Performance
By
ckennelly
5mo ago· 17 min readen
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Summary
This article from the Abseil Performance Tip of the Week series demonstrates how to use llvm-mca (Machine Code Analyzer) to analyze and optimize C++ code performance. The article explains that modern processors decompose instructions into micro-ops executed by backend units, and shows how llvm-mca can simulate instruction execution to identify performance bottlenecks. It includes practical examples of using the tool to analyze varint encoding functions and provides insights into optimizing backend-bound code through instruction-level analysis.
Key quotes
· 4 pulledThe RISC versus CISC debate ended in a draw: Modern processors decompose instructions into micro-ops handled by backend execution units.
Understanding how instructions are executed by these units can give us insights on optimizing key functions that are backend bound.
llvm-mca, short for Machine Code Analyzer, is a performance analysis tool that uses information available in LLVM to statically measure the performance of machine code for a specific CPU.
In this episode, we walk through using llvm-mca to analyze functions and identify performance insights from its simulation.
An open-source collection of core C++ library code
