Repository Analysis

chipsalliance/chisel

Chisel: A Modern Hardware Design Language

2.7 Likely human-written View on GitHub

Analysis Overview

This report presents the forensic synthetic code analysis of chipsalliance/chisel, a Scala project with 4,721 GitHub stars. SynthScan v2.0 examined 156,111 lines of code across 827 source files, recording 66 pattern matches distributed across 8 syntactic categories. The overall adjusted score of 2.7 places this repository in the Likely human-written band.

The scanner applied 160+ deterministic lexical heuristics, multi-line block detectors, abstract syntax tree depth profilers, and a cross-file Jaccard similarity matrix to construct a statistically normalised synthetic code estimate. All matches are individually weighted by severity coefficient and contextual multiplier before summation, and the resulting headline score is temporally discounted to account for the repository's development history relative to the commercial emergence of large language model coding tooling (November 2022 onward).

2.7
Adjusted Score
2.7
Raw Score
100%
Time Factor
2026-07-14
Last Push
4.7K
Stars
Scala
Language
156.1K
Lines of Code
827
Files
66
Pattern Hits
2026-07-14
Scan Date
0.04
HC Hit Rate

What These Metrics Mean

Adjusted Score
Primary synthetic code indicator. Raw score normalised per 1,000 lines of code and multiplied by the temporal discount factor. This is the definitive comparative metric — use it to rank repositories by AI authorship density.
Raw Score
The unmodified sum of all severity-weighted, context-multiplied pattern match scores before temporal discounting. Reflects the absolute signal strength independent of when the repository was last active.
Time Factor
The temporal discount multiplier (0–100%) applied to the raw score. Repositories last updated before ChatGPT's launch (Nov 2022) receive a 5% factor. Full signal is only assigned to repositories active in the post-adoption era (Jan 2024+).
Pattern Hits
Total count of individual pattern matches across all files and categories. A high hit count with a low score may indicate a very large codebase with isolated AI snippets; a low count with a high score indicates dense, concentrated AI signatures.
HC Hit Rate
High+Critical pattern hits per file, averaged across the repository. This orthogonal signal catches repositories where a few files are densely packed with high-severity AI tells — a strong indicator even when the normalised score appears moderate due to codebase size.
Lines of Code / Files
Total lines and files analysed. The scanner examines 94 file extensions. These denominators are used to normalise the score, enabling fair comparison between repositories of vastly different sizes.

Score History

Longitudinal tracking requires multiple scan runs. Once this repository is re-scanned after new commits land, this chart will visualise how the synthetic code signal evolves over time — enabling you to detect whether AI authorship is growing, stabilising, or being actively corrected by human engineers.

No multi-scan history yet — run the scanner again to build trend data.

Severity Breakdown

Classifies detected patterns by their diagnostic confidence and structural impact. CRITICAL patterns (coefficient 10) represent definitive synthetic signatures — hallucinated imports, explicit LLM attribution metadata — virtually never produced by human authors. HIGH (5) indicates strong structural tells such as cross-file repetition or cross-linguistic idioms. MEDIUM (2) covers recognisable conversational padding and AI-specific vocabulary. LOW (1) captures subtle indicators like tautological comments and generic boilerplate that require density to carry independent signal.

CRITICAL 31HIGH 0MEDIUM 2LOW 33

Directory Score Breakdown

This horizontal bar chart decomposes the repository's raw synthetic code score by top-level directory, allowing you to pinpoint precisely which modules or components carry the highest AI authorship density. Directories with disproportionately high scores relative to their size warrant targeted manual review: concentrated AI signatures often trace back to mass-generated configuration layers, auto-ported test suites, LLM-scaffolded boilerplate classes, or entire subsystems authored under heavy copilot assistance. Use this view to prioritise your human code-review effort.

Pattern Findings

The scanner identified 66 distinct pattern matches across 8 syntactic categories. Each entry below represents a discrete location in the source code where the engine recorded a statistically significant AI authorship indicator. Expand any category row to inspect the individual file paths, line numbers, code snippets, and the lexical context (CODE, COMMENT, or STRING) in which each match was detected.

Reading the findings table: The Severity column indicates the diagnostic confidence level (CRITICAL / HIGH / MEDIUM / LOW). The Context column identifies whether the match occurred inside executable code, an inline comment, or a string literal — comment-context matches receive a ×1.5 weight because LLMs systematically over-annotate. The ⚡ bolt icon marks clustered matches: three or more patterns within a 10-line window, each receiving an additional ×1.5 density multiplier as dense clusters constitute far stronger evidence of synthetic authorship than isolated hits.

Hallucination Indicators31 hits · 360 pts
SeverityFileLineSnippetContext
CRITICAL…chisel3/experimental/SerializableModuleGenerator.scala73 !generator.getConstructors.head.getParameterTypes.last.toString.contains("$"),CODE
CRITICALsrc/test/scala/chiselTests/MultiClockSpec.scala129 svsim.verilator.Backend.CompilationSettings.default.withDisabledWarnings(Seq("MULTIDRIVEN"))CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala63 assert(dut.io.out.bits.cmp.peekValue().asBigInt == expectedCmp.litValue)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala64 assert(dut.io.out.bits.cmp.peek() == expectedCmp)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala65 assert(dut.io.out.bits.vSum.zip(expectedVSum).forall { case (portEl, expEl) =>CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala68 assert(dut.io.out.bits.vSum.peek().litValue == expectedVSum.litValue)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala69 assert(dut.io.out.bits.vOutProduct.zip(expVecProduct).forall { case (portVecEl, expVecEl) =>CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala115 dut.io.out.bits.c.expect(expectedScalar)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala116 dut.io.out.bits.c.expect(expectedScalar.U)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala117 dut.io.out.bits.c.expect(expectedScalar.U(w.W))CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala118 dut.io.out.bits.cmp.expect(expectedCmp)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala121 dut.io.out.bits.vSum.expect(expectedVSum)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala126 dut.io.out.bits.vOutProduct.expect(expVecProduct)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala166 dut.io.out.bits.c.expect(3) // correctCODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala167 dut.io.out.bits.c.expect(5.U) // incorrectCODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala170 thrown.getMessage must include("dut.io.out.bits.c.expect(5.U)")CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala191 dut.io.out.bits.c.expect(5.U, ExpectationValueFormat.Hex)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala216 dut.io.out.bits.c.expect(5.U, ExpectationValueFormat.Bin)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala253 dut.io.out.bits.c.expect(jumpInst.U(w.W), customFormat)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala281 dut.io.out.bits.c.expect(5.U, customFormat)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala306 dut.io.out.bits.c.expect(BigInt(5), "bigint message")CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala331 dut.io.out.bits.c.expect(5.U, ExpectationValueFormat.Hex)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala353 dut.io.out.bits.c.expect(5.U, ExpectationValueFormat.Dec)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala375 dut.io.out.bits.c.expect(5.U)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala489 dut.io.out.bits.vOutProduct.expectPartial(expVecProductPartial)CODE
CRITICAL…test/scala/chiselTests/simulator/PeekPokeAPISpec.scala572 dut.io.out.bits.vOutProduct.expectPartial(expVecProductPartial)CODE
CRITICAL…la/chiselTests/simulator/scalatest/ChiselSimSpec.scala396 svsim.verilator.Backend.CompilationSettings.default.withTraceStyle(CODE
CRITICAL…la/chiselTests/simulator/scalatest/ChiselSimSpec.scala413 svsim.verilator.Backend.CompilationSettings.default.withTraceStyle(CODE
CRITICAL…la/chiselTests/simulator/scalatest/ChiselSimSpec.scala417 svsim.verilator.Backend.CompilationSettings.TraceKind.Fst(Some(2)),CODE
CRITICAL…n/scala/chisel3/util/experimental/decode/decoder.scala102 chisel3.util.experimental.decode.TruthTable.fromString(CODE
CRITICALsrc/main/scala/chisel3/simulator/scalatest/Cli.scala83 svsim.vcs.Backend.CompilationSettings.TraceSettings.FsdbSettings(CODE
Over-Commented Block15 hits · 15 pts
SeverityFileLineSnippetContext
LOW…main/scala-2/chisel3/experimental/SourceInfoIntf.scala1// SPDX-License-Identifier: Apache-2.0COMMENT
LOWcore/src/main/scala/chisel3/Aggregate.scala1101 def elements: SeqMap[String, Data]COMMENT
LOWcore/src/main/scala/chisel3/package.scala121 */COMMENT
LOWsvsim/src/main/resources/simulation-driver.cpp21 * required (or recommended) to wait until receiving a message in response to aCOMMENT
LOWsvsim/src/main/resources/simulation-driver.cpp41#include "verilated-sources/VsvsimTestbench__Dpi.h"COMMENT
LOWsvsim/src/main/resources/simulation-driver.cpp81 // can be sent prior to receiving this message.COMMENT
LOWsvsim/src/main/resources/simulation-driver.cpp101 // Sent in response to the LOG command. The length of the log is providedCOMMENT
LOWsvsim/src/main/resources/simulation-driver.cpp121 COMMAND_GET_BITS = 'G',COMMENT
LOWsvsim/src/main/resources/simulation-driver.cpp141 // if the sentinel port is set to the specified value.COMMENT
LOWwebsite/docusaurus.config.js21 // same name as their parent directory or have the name `index.md` now mapCOMMENT
LOW…cala-2/chisel3/internal/naming/NamingAnnotations.scala1// SPDX-License-Identifier: Apache-2.0COMMENT
LOWsrc/test/scala/chiselTests/BundleSpec.scala201 "(a=UInt<8>(8), b=Bool(true), c=UInt<4>(DontCare)) contains DontCare"COMMENT
LOWsrc/main/scala/chisel3/util/SparseVec.scala141COMMENT
LOWsrc/main/scala/chisel3/util/SparseVec.scala161 // Index -> DenseVecIndex -> DenseVec(index)COMMENT
LOWsrc/main/scala/chisel3/simulator/Simulator.scala341 case error: Throwable =>COMMENT
Verbosity Indicators6 hits · 14 pts
SeverityFileLineSnippetContext
LOWcore/src/main/scala/chisel3/internal/Error.scala86 // Step 1: Remove elements from the top in the package trimlistCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala91 // Step 2: Optionally remove elements from the bottom until the anchorCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala94 // Step 3: Remove elements from the bottom in the package trimlistCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala96 // Step 4: Reverse back to the original orderCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala99 // Step 5: Add ellipsis stack trace elements and "--full-stacktrace" infoCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala107 // Step 6: Mutate the stack trace in this exceptionCOMMENT
Structural Annotation Overuse6 hits · 14 pts
SeverityFileLineSnippetContext
LOWcore/src/main/scala/chisel3/internal/Error.scala86 // Step 1: Remove elements from the top in the package trimlistCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala91 // Step 2: Optionally remove elements from the bottom until the anchorCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala94 // Step 3: Remove elements from the bottom in the package trimlistCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala96 // Step 4: Reverse back to the original orderCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala99 // Step 5: Add ellipsis stack trace elements and "--full-stacktrace" infoCOMMENT
LOWcore/src/main/scala/chisel3/internal/Error.scala107 // Step 6: Mutate the stack trace in this exceptionCOMMENT
AI Slop Vocabulary2 hits · 6 pts
SeverityFileLineSnippetContext
MEDIUM…scala/chisel3/experimental/hierarchy/Instantiate.scala41 // A more complete and robust solution would require either refining hashCode and equality on DataCOMMENT
MEDIUM.github/workflows/release-notes.yml42 # Put output through env variable to make it robust to quotesCOMMENT
Unused Imports3 hits · 3 pts
SeverityFileLineSnippetContext
LOWlit/tests/lit.cfg.py1CODE
LOWlit/tests/lit.cfg.py3CODE
LOWlit/tests/lit.cfg.py4CODE
Hyper-Verbose Identifiers2 hits · 2 pts
SeverityFileLineSnippetContext
LOW…/main/scala/chisel3/internal/BuilderContextCache.scala25 def getOrElse[A](key: Key[A], default: => A): A = cache.getOrElse(key, default).asInstanceOf[A]CODE
LOW…/main/scala/chisel3/internal/BuilderContextCache.scala31 def getOrElseUpdate[A](key: Key[A], default: => A): A = cache.getOrElseUpdate(key, default).asInstanceOf[A]CODE
Slop Phrases1 hit · 2 pts
SeverityFileLineSnippetContext
LOW…/chiselTests/experimental/hierarchy/InstanceSpec.scala1041 // TODO don't forget to test this with heterogeneous Views (eg. viewing a tuple of a port and non-port as a single BunCOMMENT