v7.0

Highlights

This release completes support for the changes in the recently released IEEE 1800-2023 version of the SystemVerilog LRM.

Language Support

• Select expressions of packed arrays now always return an unsigned type, as mandated by the LRM
• Clocking skew delays now properly require a constant value
• Enforce that static methods can't have override specifiers
• The error for invalid state-dependent path conditions in specify blocks can now be downgraded with -Wspecify-condition-expr for compatibility with other tools
• Added support for the optional system tasks and functions from Annex D in the LRM: $countdrivers, $list, $input, $key, $nokey, $reset, $reset_count, $reset_value, $save, $incsave, $restart, $scope, $scale, $showscopes, $showvars, $sreadmemb, $sreadmemh, $getpattern
• Added support for the optional compiler directives from Annex E in the LRM: `default_decay_time, `default_trireg_strength, `delay_mode_distributed, `delay_mode_path, `delay_mode_unit, `delay_mode_zero
• Rules about nondegeneracy of sequences and properties are now enforced (thanks to @likeamahoney)
• Special case rules about how name resolution works in bind directives are now enforced
• Changed the definition of "simple types" to include string to allow using it as a target for assignment pattern fields (thanks to @likeamahoney)
• Rules for inconsistent net types connected via an implicit named port connection are now enforced (thanks to @likeamahoney)

Clarifications in IEEE 1800-2023

• Assertion clocking events can't reference automatic variables
• The .* token sequence is actually two separate tokens that can be separated by whitespace
• Functions in constraints cannot have inout arguments
• Constraint subexpression can be of any type as long as their final expression type is numeric and they don't reference random variables
• The argument to $isunbounded must be a parameter name (only enforced as a pedantic warning in slang)
• Edge-sensitive paths in specify blocks can specify an edge keyword without also including a data source expression
• Only bidirectional switches allow connections to nets with user-defined net types (other primitives do not)

New Features in IEEE 1800-2023

• Constraint expressions and random variables can have real types
• dist expressions can have a default specifier
• dist expressions can have real types
• solve-before constraints can specify array.size() as well as regular random variables
• disable soft constraints can target array.size()
• Constraint blocks can have override specifiers (initial / extends / final)
• Covergroups can inherit from covergroups in parent classes
• Coverpoints can have real types
• Covergroups have new options: cross_retain_auto_bins and real_interval
• New system functions $timeunit, $timeprecision, and $stacktrace

General Features

• Added -Wunsigned-arith-shift which warns about suspicious arithmetic right shifts of unsigned types
• Added -Wstatic-init-order and -Wstatic-init-value which warn about static initializers that depend on uninitialized values or an undefined order of other static initializers
• Added -Wfloat-int-conv and -Wint-float-conv which warn about implicit conversions between floating point and integer types
• Added -Wfloat-narrow and -Wfloat-widen which warn about implicit conversions between floating point types of differing widths
• Added -Wunused-import and -Wunused-wildcard-import which warn about unused import directives
• Added -Warith-op-mismatch, -Wbitwise-op-mismatch, -Wcomparison-mismatch, and -Wsign-compare which all warn about different cases of mismatched types in binary expressions
• slang-netlist has experimental support for detecting combinatorial loops (thanks to @udif)
• Added --allow-merging-ansi-ports (included in "vcs" compat mode) which allows non-standard behavior in which ANSI module ports can duplicate net and variables declared within the module
• Added --ast-json-source-info which includes source line information when dumping an AST to JSON (thanks to @KennethDRoe)
• Added --enable-legacy-protect which enables support for nonstandard / legacy protected envelopes: Verilog-XL style `protect directives and Verilog-A style // pragma protect comments

Improvements

• Default value expressions for parameters that are overridden are now checked for basic correctness and other parameters they reference will not warn for being "unused"
• Made several minor improvements to the locations reported for propagated type conversion warnings
• Sped up Compilation object construction by reorganizing how system subroutines are created and registered
• Improved the parser error reported when encountering an extraneous end delimiter in a member list
• Various fixes and improvements were made to slang-netlist (thanks to @jameshanlon, @udif)
• Added options to slang-tidy to better control what gets output (thanks to @Sustrak)
• Added a bunch of new checks to slang-tidy (thanks to @JoelSole-Semidyn)
• Improved handling of source files that contain non-UTF8 comments (thanks to @udif)
• Fixed and improved various parts of the SyntaxRewriter API (thanks to @sgizler)

Fixes

• Fixed several AST serialization methods (thanks to @tdp2110, @likeamahoney, @Kitaev2003, @cyuzuzo-j)
• Fixed the return type of DPI import tasks
• Fixed a bug that caused some inout ports to warn as "unused"
• Fixed the checking of the extends override specifier when the containing class has no base class
• Fixed a case where bracketed delay expressions in sequence concatenations were not checked for correctness
• Fixed the type of the iterators used in with-expressions for covergroup bins
• Fixed a bug that sometimes prevented printing the correct scope for type alias names in diagnostic messages
• Fixed the hierarchical path string created for symbols inside of unnamed generate blocks (thanks to @povik)
• Fixed spurious errors that could occur when using generic class instantiations inside uninstantiated generate blocks
• Correctly disallow passing expressions of void type to format style system functions (thanks to @tdp2110)
• Fixed a bug where parameters that referred to themselves via hierarchical reference would cause a crash instead of reporting a diagnostic
• Fixed PATHPULSE$ specparam initializers to allow providing only one value instead of requiring two (thanks to @likeamahoney)
• Fixed PLA tasks to accept concatenation expressions as arguments without reporting an error about the direction of the argument bounds (thanks to @likeamahoney)
• Fixed a bug that could cause spurious errors in uninstantiated generic class definitions
• Fixed the Symbol::getHierarchicalPath API to round-trip correctly
• Fixed JSON serialization of integers to round-trip correctly
• Fixed a bug in resolving defparam values inside of generate loops
• Fixed checking of event arguments in system timing check functions
• Fixed checking of deferred assertion function calls (thanks to @likeamahoney)
• Correctly issue an error if a sequence or property has a formal argument with the same name as a local variable declaration (thanks to @likeamahoney)
• Fixed a case of recursive property instantiation that was incorrectly disallowed (thanks to @likeamahoney)
• Fixed bugs in checking for overlapping user-defined primitive table rows (thanks to @likeamahoney)
• Fixed infinite loops in the parser when encountering constraint blocks with certain kinds of invalid tokens in them (thanks to @likeamahoney)
• Fixed errors in assigning to select expressions involving members of virtual interfaces (thanks to @micron-ian)