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Suppress WIDTH warning on negate using carry bit (#2395). [Peter Monsson]

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This commit is contained in:
Wilson Snyder 2022-02-13 15:27:31 -05:00
parent 7a355d448a
commit 77e68acf54
3 changed files with 13 additions and 2 deletions
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@ -15,6 +15,7 @@ Verilator 4.219 devel
* Removed the deprecated lint_off flag -msg; use -rule instead.
* Removed the deprecated "fl" attribute in XML output; use "loc" attribute instead.
* Suppress WIDTH warning on negate using carry bit (#2395). [Peter Monsson]
* Fix skipping public enum values with four-state values (#3303).

11
src/V3Width.cpp
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@ -5049,7 +5049,7 @@ private:
void visit_negate_not(AstNodeUniop* nodep, bool real_ok) {
// CALLER: (real_ok=false) Not
// CALLER: (real_ok=true) Negate
// CALLER: (real_ok=true) Negate - allow real numbers
// Signed: From lhs
// IEEE-2012 Table 11-21:
// Widths: out width = lhs width
@ -5076,7 +5076,14 @@ private:
AstNodeDType* const expDTypep = m_vup->dtypeOverridep(nodep->dtypep());
nodep->dtypep(expDTypep); // Propagate expression type to negation
AstNodeDType* const subDTypep = expDTypep;
iterateCheck(nodep, "LHS", nodep->lhsp(), CONTEXT, FINAL, subDTypep, EXTEND_EXP);
// Some warning suppressions
bool lhsWarn = true;
if (VN_IS(nodep, Negate)) {
// Warn if user wants extra bit from carry
if (subDTypep->widthMin() == (nodep->lhsp()->widthMin() + 1)) lhsWarn = false;
}
iterateCheck(nodep, "LHS", nodep->lhsp(), CONTEXT, FINAL, subDTypep, EXTEND_EXP,
lhsWarn);
}
}

3
test_regress/t/t_lint_width.v
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@ -13,6 +13,9 @@ module t ();
wire [4:0] sumb = 1'b1 + five;
wire [4:0] sumc = five - 1'b1;
wire [4:0] neg5 = - five;
wire [5:0] neg6 = - five;
// Relatively harmless < or <= compared with something less wide
localparam [1:0] THREE = 3;
int a;