CAES Language for Synchronous Hardware

Version on this page:0.5.11
LTS Haskell 9.21:0.7.2
Stackage Nightly 2018-06-20:0.99.1
Latest on Hackage:0.99.1

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BSD2 licensed by Christiaan Baaij
Maintained by Christiaan Baaij

Module documentation for 0.5.11

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clash-ghc - Haskell/GHC front-end for the CλaSH compiler

  • See the LICENSE file for license and copyright details
  • Contains code from the GHC compiler, see the LICENSE_GHC file for license and copyright details pertaining to that code.

CλaSH - A functional hardware description language

CλaSH (pronounced ‘clash’) is a functional hardware description language that borrows both its syntax and semantics from the functional programming language Haskell. The CλaSH compiler transforms these high-level descriptions to low-level synthesizable VHDL, Verilog, or SystemVerilog.

Features of CλaSH:

  • Strongly typed (like VHDL), yet with a very high degree of type inference, enabling both safe and fast prototying using consise descriptions (like Verilog).

  • Interactive REPL: load your designs in an interpreter and easily test all your component without needing to setup a test bench.

  • Higher-order functions, with type inference, result in designs that are fully parametric by default.

  • Synchronous sequential circuit design based on streams of values, called Signals, lead to natural descriptions of feedback loops.

  • Support for multiple clock domains, with type safe clock domain crossing.


For updates and questions join the mailing list or read the forum


Changelog for the clash-ghc package

0.99.1 May 12th 2018

  • Allow ~NAME[N] tag inside ~GENSYM[X]
  • Support HDL record selector generation #313
  • InlinePrimitive support: specify HDL primitives inline with Haskell code

0.99 March 31st 2018

  • New features: Support for clash-prelude-0.99: Explicit clock and reset arguments Overhaul of TopEntity annotations Hierarchies with multiple synthesisable boundaries by allowing more than one function in scope to have a Synthesize annotation. Local caching of functions with a Synthesize annotation Bit type is mapped to a HDL scalar type (e.g. std_logic in VHDL) Improved name preservation Zero-bit values are filtered out of the generated HDL * Improved compile-time computation
  • Many bug fixes


  • New features: * Sum-of-product types: unused bits now "don't-care" #212
  • Fixes bugs: * Eagerness bug in regEn #104 (Thanks to @cbiffle)

0.7.1 April 11th 2017

  • New features: Support distribution of primitive templates with Cabal/Hackage packages commit Find memory data files and primitive files relative to import dirs (-i<DIR>) * Add 'clashi' program and 'clash-ghc' package #208, thanks to @thoughtpolice
  • Fixes bugs: case (EmptyCase ty) of ty' { ... } -> EmptyCase ty' #198 BitVector.split# apply the correct type arguments *January 17th 2017

  • Fixes bugs: * Include HsVersions.h in source distribution

0.7 January 16th 2017

  • New features: Support for clash-prelude 0.11 Primitive templates can include QSys files VHDL blackboxes: support additional libraries and uses keywords in generated VHDL Highly limited Float/Double support (literals and Rational conversion), hidden behind the -clash-float-support flag.
  • Fixes bugs: Reduce type families inside clock period calculation #180 Only output signed literals as hex when they're multiple of 4 bits #187 * Correctly print negative hex literals

0.6.24 *October 17th 20168

  • Call generatePrimMap after loadModules #175
  • Fixes bugs: (System)Verilog: CLaSH.Sized.Vector.imap primitive gets indices in reverse order Template Haskell splices are run twice * CLaSH errors out when observing the constructor for Signal #174

0.6.23 August 18th 2015

  • Fixes bugs: Type families are not being reduced correctly #167 (System)Verilog: Fix primitives for {Signed,Unsigned} rotateL# and rotateR# #169

0.6.22 August 3rd 2016

  • Fixes bugs: Bug in DEC transformation overwrites case-alternatives Bug in DEC transformation creates non-representable let-binders VHDL: Incorrect primitive for Integers ltInteger# and geInteger# (System)Verilog: Fix primitive for CLaSH.Sized.Internal.Signed.mod# and GHC.Type.Integer.modInteger #164

0.6.21 July 19th 2016

  • Fixes bugs: Rounding error in logBase calculation VHDL: Incorrect primitive for Indexs *# * VHDL: Incorrect handling of Indexs fromInteger# and maxBound# primitives for values larger than 2^MACHINE_WIDTH

0.6.20 July 15th 2016

  • New features: * Better error location reporting
  • Fixes bugs: CLaSH.Sized.Internal.Unsigned.maxBound# not evaluated at compile-time #155 CLaSH.Sized.Internal.Unsigned.minBound# not evaluated at compile-time #157 Values of type Index 'n', where 'n' > 2^MACHINE_WIDTH, incorrectly considered non-synthesisable due to overflow VHDL: Types in generated types.vhdl incorrectly sorted * Casts of CLaSH numeric types result in incorrect VHDL/Verilog (Such casts are now reported as an error)

0.6.19 June 9th 2016

  • Fixes bugs: Eq instance of Vec sometimes not synthesisable VHDL: Converting product types to stdlogicvector fails when the clash-hdlsyn Vivado flag is enabled

0.6.18 June 7th 2016

  • New features: DEC transformation also lifts HO-primitives applied to "interesting" primitives (i.e. zipWith (*)) New -clash-hdlsyn Xilinx flag to generate HDL tweaked for Xilinx synthesis tools (both ISE and Vivado)
  • Fixes bugs: replicate unfolded incorrectly #150 imap is not unrolled #151 * VHDL: Incorrect primitive specification for snatToInteger #149

0.6.17 April 7th 2016

  • New features: * Up to 2x reduced compilation times when working with large Vec literals
  • Fixes bugs: VHDL: Incorrect primitives for BitVectors quot# and rem# VHDL: Bit indexing and replacement primitives fail to synthesise in Synopsis tools Bug in DEC transformation throws CLaSH into an endless loop #140 Missed constant folding opportunity results in an error #50

0.6.16 March 21st 2016

  • New features: * Also generate testbench for circuits without input ports #135
  • Fixes bugs: * clockWizard broken #49

0.6.15 March 15th 2016

  • Fixes bugs: * XST cannot finds "_types" package unless it is prefixed with "work." #133

0.6.14 March 15th 2016

  • Fixes bugs: * XST cannot finds "_types" package unless it is prefixed with "work." #133

0.6.13 March 14th 2016

  • Fixes bugs: * Not all lambda's in a function position removed

0.6.12 March 14th 2016

  • Fixes bugs: * Not all lambda's in a function position removed due to bad eta-expansion #132

0.6.11 March 11th 2016

  • New features: Add support for HDL synthesis tool specific HDL generation: New -clash-hdlsyn Vivado flag to generate HDL tweaked for Xilinx Vivado * Preserve more Haskell names in generated HDL #128
  • Fixes bugs: VHDL: Vivado fails to infer block ram #127 Users must use the -clash-hdlsyn Vivado flag in order to generate Xilinx Vivado specific HDL for which Vivado can infer block RAM.

0.6.10 February 10th 2016

  • New features: hdl files can be written to a directory (set by the -clash-hdldir flag) other than the current working directory #125. Also respects the -outputdir directory, unless: -clash-hdldir is set to a different directory. * -hidir, -stubdir, and -dumbdir are not the same directory as -odir
  • Fixes bugs: caseCon transformation does not work on non-exhaustive case-expressions #123 VHDL: insufficient type-qualifiers for concatenation operator #121 * Primitive reductions don't look through Signal #126

0.6.9 January 29th 2016

  • New features: * Support for Debug.Trace.trace, thanks to @ggreif

  • Fixes bugs: case undefined of ... should reduce to undefined #116 VHDL/SystemVerilog: BlockRAM elements must be bit vectors #113 * Type families obscure eligibility for synthesis #114

0.6.8 January 13th 2016

  • New features: Support for Haskell's: Char, Int8, Int16, Int32, Int64, Word, Word8, Word16, Word32, Word64. Int/Word/Integer bitwidth for generated HDL is configurable using the -clash-intwidth=N flag, where N can be either 32 or 64.
  • Fixes bugs: * Cannot reduce case error ... of ... to error ... #109

0.6.7 December 21st 2015

  • Support for unbound-generics-0.3
  • New features: * Only look for 'topEntity' in the root module. #22
  • Fixes bugs: * Unhelpful error message when GHC is not in PATH #104

0.6.6 December 11th 2015

  • New features: Remove all existing HDL files before generating new ones. This can be disabled by the -clash-noclean flag. #96 Support for clash-prelude 0.10.4

0.6.5 November 17th 2015

  • Fixes bugs: Integer literals used as arguments not always properly annotated with their type. Verilog: Name collision in verilog code #93 (System)Verilog: Integer literals missing "32'sd" prefix when used in assignments. VHDL: Integer literals should only be capped to 32-bit when used in assignments. * Verilog: HO-primitives incorrect for nested vectors.

0.6.4 November 12th 2015

  • Fixes bugs: Reversing alternatives is not meaning preserving for literal patterns #91 DEC: root of the case-tree must contain at least 2 alternatives #92 * Do not generate overlapping literal patterns in VHDL #91

0.6.3 October 24th 2015

  • New features: * Improve DEC transformation: consider alternatives before the subject when checking for disjoint expressions.
  • Fixes bugs: * DEC: don't generate single-branch case-expressions #90

0.6.2 October 21st 2015

  • New features: * Support clash-prelude 0.10.2

  • Fixes bugs: CLaSH interpreter was reading '.ghci' file instead of '.clashi' file #87 DEC: Subject and alternatives are not disjoint #88

0.6.1 October 16th 2015

  • New features: Support for clash-prelude 0.10.1 Transformation that lifts applications of the same function out of alternatives of case-statements. e.g.

    `haskell case x of A -> f 3 y B -> f x x C -> h x `

    is transformed into:

    `haskell let f_arg0 = case x of {A -> 3; B -> x} f_arg1 = case x of {A -> y; B -> x} f_out = f f_arg0 f_arg1 in case x of A -> f_out B -> f_out C -> h x `

  • Fixes bugs: clash won't run when not compiled with usual ghc #82 Fail to generate VHDL with blockRamFile' in clash-ghc 0.6 #85 * Case-statements acting like normal decoder circuits are erroneously synthesised to priority decoder circuits.

0.6 October 3rd 2015

  • New features: Support clash-prelude-0.10 Pattern matching on CLaSH.Sized.Vector's :> is now supported * Unroll "definitions" of the following primitives: fold, dfold, foldr

0.5.15 September 21st 2015

  • New features: * Report simulation time in (System)Verilog assert messages

  • Fixes bugs: Performance bug: top-level definitions of type "Signal" erroneously inlined. Fix Index maxBound #79

0.5.14 September 14th 2015

  • New features: * Completely unroll "definitions" of some higher-order primitives with non-representable argument or result vectors: It is now possible to translate e.g. f xs ys = zipWith ($) (map (+) xs) ys :: Vec 4 Int -> Vec 4 Int -> Vec 4 Int

  • Fixes bugs: Converting Bool to Unsigned generates broken VHDL #77 topLet transformation erroneously not performed in a top-down traversal Specialisation limit unchecked on types and constants Vector of functions cannot be translated #25 * CLaSH fails to generate VHDL when map is applied #78

0.5.13 September 8th 2015

  • Fixes bugs: Cannot translate GHC MachLabel literal Maybe (Index n) not translatable to VHDL #75

0.5.12 September 7th 2015

  • New features: * Modest compilation time speed-up. Compilation time of the I2C module on my machine went down from 43s to 24s, and maximum memory usage went down from 840 MB to 700 MB.

  • Fixes bugs: Bug in VHDL ROM generation #69 Clash running out of memory on Simple-ish project #70 Fix asyncRom VHDL primitive #71 Fix primitive for CLaSH.Sized.Internal.Signed.size# #72 * rem and quot on Signed are broken #73

0.5.11 August 2nd 2015

  • New features: * Re-enable GHC's strictness analysis pass, which improves dead-code removal, which hopefully leads to smaller circuits.

0.5.10 July 9th 2015

  • New features: Use new VHDL backend which outputs VHDL-93 instead of VHDL-2002: generated VHDL is now accepted by a larger number of tools. Treat all so-called bottom values (error "FOO", let x = x in x, etc.) occuring in installed libraries as undefined. Before, there were (very) rare situations where we couldn't find the expressions belonging to a function and demanded a BlackBox, even though we knew the expression would be a bottom value. Now, we stop demanding a BlackBox for such a function and simply treat it as undefined, thus allowing a greater range of circuit descriptions that we can compile.

0.5.9 June 26th 2015

  • New features: * Use new verilog backend which outputs Verilog-2001 instead of Verilog-2005: generated Verilog is now accepted by Altera/Quartus

  • Fixes bugs: * --systemverilog switch incorrectly generates verilog code instead of systemverilog code

0.5.8 June 25th 2015

  • New features: Support for copying string literals from Haskell to generated code Support clash-prelude-0.9 * Size at below which functions are always inlined is configurable, run with -clash-inline-below=N to set the size limit to N

0.5.7 June 3rd 2015

  • New features: New Verilog backend, run :verilog in interactive mode, or --verilog for batch mode Generated component names are prefixed by the name of the module containing the topEntity

0.5.6 May 18th 2015

  • New features: Inlining limit is configurable, run with -clash-inline-limit=N to set the inlining limit to N Specialisation limit is configurable, run with clash-spec-limit=N to set the inline limit to N * Debug level is configurable, run with -clash-debug <LEVEL> where <LEVEL> can be: DebugNone, DebugFinal, DebugName, DebugApplied, DebugAll. Be default, clash runs with DebugNone.

  • Fixes bugs: * Extend evaluator for GHC.Integer.Type.minusInteger and CLaSH.Promoted.Nat.SNat.

0.5.5 May 5th 2015

  • New features: * TopEntity wrappers are now specified as ANN annotation pragmas #42

0.5.4 May 1st 2015

  • New features: * Generate wrappers around topEntity that have constant names and types

0.5.3 April 24th 2015

  • Fixes bugs: * Fix bug where not enough array type definitions were created by the VHDL backend

0.5.2 April 21st 2015

  • Use latest ghc-typelits-natnormalise

0.5.1 April 20th 2015

  • New features: GHC 7.10 support Update to clash-prelude 0.7.2 * Use typechecker plugin for better type-level natural number handling

0.5 March 11th 2015

  • New features: * SystemVerilog backend. #45

0.4.1 February 4th 2015

  • Include bug fixes from clash-lib 0.4.1

0.4 November 17th 2014

  • New features: * Support for clash-prelude 0.6

  • Fixes bugs: * clash-ghc ignores "-package-db" flag #35

0.3.3 August 12th 2014

  • Fixes bugs: * Compile with GHC 7.8.3 #31

0.3.2 June 5th 2014

  • Fixes bugs: Type synonym improperly expanded #17 BlackBox for Signed maxBound and minBound generate incorrect VHDL. #19 * Generate failure code in the VHDL for recSelError #23

0.3.1 May 15th 2014

  • New features: Hardcode fromInteger for Signed and Unsigned #9 Better blackbox operation for vindex #12 * Replace VHDL default hole by error hole #13

  • Fixes bugs: Update GHC2Core.hs #1 primitives (clash.sized.vector) #2 Type families are not expanded #3 Incorrect vhdl generation for default value in blackbox #6 * Missing begin keyword in Signed/Unsigned JSON files #16

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