CGF Format

Concept

The CGF (Coverage Group Format) is the coverpoint specification language used by RISCV-ISAC to express architectural coverage goals. It allows coverpoints to be written as pure Python expressions over instruction fields and is consumed by RISCV-CTG to drive Constraint Satisfaction Problem (CSP) solving for test generation.

First seen 7/3/2026

Last seen 7/3/2026

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CGF Format

Overview

The CGF (Coverage Group Format) is the coverpoint specification format defined and used by RISCV-ISAC. A coverpoint in CGF specifies a boolean expression over the fields of an architectural element (instruction or architectural state) that must be covered during execution of a test ^[1].

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RISCV-ISAC ← uses 95% 1e

RISCV-ISAC defines and uses the CGF format for coverage specification.

RISCV-CTG ← uses 95% 1e

RISCV-CTG uses the CGF format defined by ISAC to generate tests.

ISA Coverage Specification part of → 85% 1e

The CGF format is the concrete representation of the ISA coverage specification.

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RISCV-ISAC USES Extracted graph relationship

RISCV-CTG USES Extracted graph relationship

ISA Coverage Specification PART_OF Extracted graph relationship

CITATIONS

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[1] A coverpoint specifies a boolean expression over the fields of an architectural element (instruction/state) that is required to be covered during execution. Automating Generation and Maintenance of a High-Quality Architectural Test Suite for RISC-V - CARRV at ISCA 2022

[2] In ISAC, coverpoints are expressed as pure Python expressions, in contrast to classical DV coverpoints in SV-UVM. Automating Generation and Maintenance of a High-Quality Architectural Test Suite for RISC-V - CARRV at ISCA 2022

[3] CGF coverpoints are categorized by instruction mnemonics (opcode), register operands, operand combinations, value combinations, CSR value combinations, and cross combinations. Automating Generation and Maintenance of a High-Quality Architectural Test Suite for RISC-V - CARRV at ISCA 2022

[4] Custom Python functions (abstract_comb) are resolved into standard coverpoints during normalization. Automating Generation and Maintenance of a High-Quality Architectural Test Suite for RISC-V - CARRV at ISCA 2022

[5] RISCV-CTG uses the CGF format defined by ISAC and models coverpoints as a Constraint Satisfaction Problem, solved independently for op_comb and val_comb using Min-Conflict or Backtracking solvers. Automating Generation and Maintenance of a High-Quality Architectural Test Suite for RISC-V - CARRV at ISCA 2022

[6] A #nosat suffix can be used on a coverpoint to skip the CSP solver when all instruction fields are fully defined. Automating Generation and Maintenance of a High-Quality Architectural Test Suite for RISC-V - CARRV at ISCA 2022

[7] CTG interleaves op_comb and val_comb solutions, filters test cases so that each hits at least one unique coverpoint, and substitutes values into assembly macro templates to emit assembly files. Automating Generation and Maintenance of a High-Quality Architectural Test Suite for RISC-V - CARRV at ISCA 2022

[8] ISAC evaluates coverage from an instruction trace containing instruction address, instruction encoding, and architectural state changes (CSR and register file updates). Automating Generation and Maintenance of a High-Quality Architectural Test Suite for RISC-V - CARRV at ISCA 2022