* verilog: fix string literal regular expression.
A backslash was improperly quoted, causing string literal matching
to fail when the final token before a closing quote was an escaped
backslash.
* verilog: add regression test for string literal regex bug.
Test for bug triggered by escaped backslash immediately before
closing quote (introduced in ca7d94af and fixed by 40aa7eaf).
Fix buggy memory allocation introduced in #5152:
1) clean up ast_stack to reflect AST node rearrangement when necessary,
to avoid dangling pointer;
2) call free_attr() on unused attribute list when no new syntax node is
created, to avoid leaking it.
* verilog: fix string literal regular expression.
A backslash was improperly quoted, causing string literal matching
to fail when the final token before a closing quote was an escaped
backslash.
* verilog: add regression test for string literal regex bug.
Test for bug triggered by escaped backslash immediately before
closing quote (introduced in ca7d94af and fixed by 40aa7eaf).
The implementation for the implication operator in cover mode actually
implements the followed-by operator, so we can re-use it unchanged.
It is not always the correct behavior for the implication operator in
cover mode, but a) it will only cause false positives not miss anything
so if the behavior is unexpected it will be visible in the produced
traces, b) it is unlikely to make a difference for most properties one
would practically use in cover mode, c) at least one other widely used
SVA implementations behaves the same way and d) it's not clear whether
we can fix this without rewriting most of verificsva.cc
Use a greedy regular expression to match input inside a string
literal, so that flex can accumulate a longer match instead of
invoking a rule for each individual character.
There are two elements involved:
1) Apply the relevant full_case and/or parallel_case attribute(s) to
the generated AST_CASE node(s), so that the existing AST frontend and
subsequent passes will generate RTLIL with appropriate behaviour.
(This is handled in the parser "if_attr" non-terminal.)
2) Rearrange the AST_CASE structure when necessary. For "priority if"
(i.e., full_case), this requires only ensuring that directly nested
"else if" branches also inherit the full_case attribute. For
"unique if" and "unique0 if" (i.e., parallel_case+full_case and
parallel_case alone), there are two steps:
a) Flatten the AST_CASE structure such that any direct "else if"
branches are mapped to additional AST_CONDs in the parent;
b) Reverse the "direction" of the test: the constant 1 (true)
is provided in the AST_CASE node, and the expression(s) in the
if statement(s) are given in each AST_COND. This is necessary
because the constant 1, being the common factor, must occupy the
shared AST_CASE position.
(This is handled in the parser "TOK_IF" expansion of behavioral_stmt.)
Observe that:
* The generated AST has not been changed for bare "if"s (those
without unique/priority). This should minimise the risk of
unexpected regressions.
* It is possible that the flattening described in 2) a) above might
affect the behaviour of expressions with side effects in "unique if"
statements (consider "unique if( a ) ...; else if( b++ ) ...": if
a is true, is b incremented?). While it might be possible to provide
precise semantics here, IEEE 1800-2012 12.4.2 seems to be deliberately
vague ("In unique-if and unique0-if, the conditions may be evaluated
and compared in any order[...] The presence of side effects in
conditions may cause nondeterministic results.") and so it seems
doubtful that there is benefit in Yosys providing stronger promises
on the interpretation of questionable code.
Add support to the "read_verilog -sv" parser to validate the
"unique", "unique0", and "priority" keywords in contexts where
they're legal according to 1800-2012 12.4.2.
This affects only the grammar accepted; the behaviour of conditionals
is not changed. (But accepting this syntax will provide scope for
possible optimisations as future work.)
Three test cases ("unique_if", "unique_if_else", and
"unique_if_else_begin") verify that the keywords are accepted where
legal and rejected where illegal, as described in the final paragraph
of 12.4.2.
`read_verilog_file_list` should not try to read arguments as selection args. Without this, trying to pass a file without a `-f|-F` flag is misleading, in the best case giving a warning about the selection not matching any module, or in worst case just doing nothing (if the filename is a valid selection).
