Constrained Random Instruction Generation

Concept

Constrained random instruction generation is the production of randomized instruction streams under validity-oriented rules rather than as arbitrary bit patterns. In the cited processor-verification flow, it appears as the first phase of simulation-based verification, feeding RTL simulation and architectural-state comparison against a golden reference model.

First seen 5/25/2026

Last seen 6/2/2026

Evidence 9 chunks

Wiki v3

WIKI

Overview

Constrained random instruction generation is a verification approach in which a test generator produces randomized instruction streams while respecting constraints. In the cited processor-verification flow, the generator creates instruction streams "based on constraints" or on coverage goals, rather than emitting unconstrained inputs.

Role in simulation-based processor verification

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RELATIONSHIPS

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riscv-dv ← implements 100% 1e

RISCV-DV generates millions of constrained-randomized RISC-V instructions.

RISC-V core ← uses 90% 1e

The RISC-V generates test instructions and data through an online constrained random process.

DiFuzzRTL ← uses 85% 1e

DifuzzRTL uses static analysis to generate instructions with required operands.

LINKED ENTITIES

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DiFuzzRTL USES Extracted graph relationship

CITATIONS

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5 citations — click to expand

[1] In typical simulation-based processor verification, the test case generator randomly generates instruction streams based on constraints or coverage. MorFuzz: Fuzzing Processor via Runtime Instruction Morphing enhanced Synchronizable Co-simulation

[2] After generation, the RTL simulator translates processor RTL into a software model and compiles it with a test harness into a host executable binary. MorFuzz: Fuzzing Processor via Runtime Instruction Morphing enhanced Synchronizable Co-simulation

[3] Correctness is determined by comparing the externally visible architectural state of the DUT with that of a golden reference model. MorFuzz: Fuzzing Processor via Runtime Instruction Morphing enhanced Synchronizable Co-simulation

[4] In the cited RISC-V context, instructions have two valid lengths: 16-bit compressed instructions and 32-bit instructions. MorFuzz: Fuzzing Processor via Runtime Instruction Morphing enhanced Synchronizable Co-simulation

[5] The paper divides RISC-V instruction fields into opcode-related and operand-related fields; funct/opcode determine the operation or opcode type, while rs, imm, and rd provide operands and destination selection. MorFuzz: Fuzzing Processor via Runtime Instruction Morphing enhanced Synchronizable Co-simulation