Posts / Tag
#objdump
3 posts
RISC-VRISC-V Decoder Design: Decode Tables, Formats, and Illegal Instructions
Part 15 of the RISC-V series. Fills in the RV32I decode table down to the control signals and defines five illegal instruction conditions, then checks it against GNU objdump on 174,608 words. 165,923 matched, and all 8,685 mismatches were explained by four causes.
RISC-VC Extension: Decompressor, 16-Bit Fetch, and Misaligned 32-Bit Instructions
Part 21 of the RISC-V series. I built the C extension's decompressor and fetch buffer in Python and checked all 49,152 16-bit values and a real rv32imc program against objdump. 36.7% of executed instructions spanned two words, and the fetch buffer cut word reads from 33,771 to 23,903.
RISC-VThe C Extension: Compressed Formats and Their 32-bit Equivalents
Part 11 of the RISC-V series. Covers the nine 16-bit formats of the C extension and their 32-bit equivalents, then checks a hand-written decompressor against objdump for all 49,152 16-bit values. In real code, 51–69% of instructions became 16-bit, shrinking code by 26–34%.