luke
/
verilator
mirror of https://github.com/verilator/verilator.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Prevent internal error for coverpoints that references a covergroup formal parameter 

Signed-off-by: Matthew Ballance <matt.ballance@gmail.com>
This commit is contained in:
Matthew Ballance 2026-07-07 01:35:49 +00:00
parent aca58ca90f
commit 8d7a331d40
3 changed files with 83 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

59
src/V3Covergroup.cpp
View File

@ -1692,21 +1692,23 @@ class FunctionalCoverageVisitor final : public VNVisitor {
}
// VISITORS
AstNode* findEnclosingMemberRef(AstClass* cgClassp) {
AstNode* findUnsupportedCoverpointRef(AstClass* cgClassp) {
// An embedded covergroup is lowered into a sibling AstClass that has no handle to
// the enclosing object. A coverpoint/iff/cross expression that references a
// (non-static) member of the enclosing class therefore emits C++ that accesses the
// member as if it were static ("invalid use of non-static data member"). Detect
// such references so the caller can skip lowering with a clean warning instead of
// producing uncompilable code. Returns the first offending node, or nullptr.
// the enclosing object. Two coverpoint/iff/cross shapes cannot be lowered and would
// otherwise emit uncompilable C++ or crash V3Broken; detect them so the caller can
// skip lowering with a clean COVERIGN warning. Returns the first offending node
// (or nullptr), preferring the enclosing-member case for message clarity.
// Collect the covergroup class's own member variables (sample/constructor args);
// references to those are legitimate.
std::set<const AstVar*> ownVars;
for (AstNode* itemp = cgClassp->membersp(); itemp; itemp = itemp->nextp()) {
if (const AstVar* const varp = VN_CAST(itemp, Var)) ownVars.insert(varp);
}
// Pass 1: a (non-static) member of the enclosing class reached with no handle. The
// member would be emitted as if it were static ("invalid use of non-static data
// member").
AstNode* offenderp = nullptr;
const auto scan = [&](AstNode* rootp) {
const auto scanEnclosing = [&](AstNode* rootp) {
rootp->foreach([&](AstVarRef* refp) {
if (offenderp) return;
const AstVar* const varp = refp->varp(); // Always set post-LinkDot
@ -1716,8 +1718,26 @@ class FunctionalCoverageVisitor final : public VNVisitor {
if (varp->isClassMember() && !ownVars.count(varp)) offenderp = refp;
});
};
for (AstCoverpoint* cpp : m_coverpoints) scan(cpp);
for (AstCoverCross* crossp : m_coverCrosses) scan(crossp);
for (AstCoverpoint* cpp : m_coverpoints) scanEnclosing(cpp);
for (AstCoverCross* crossp : m_coverCrosses) scanEnclosing(crossp);
if (offenderp) return offenderp;
// Pass 2: the coverpoint expression dereferences a class handle to reach a member,
// e.g. a parameterized covergroup 'covergroup cg(cls st); coverpoint st.test;'. The
// lowered covergroup class cannot resolve the handle argument, so lowering leaves a
// dangling VarRef and aborts in V3Broken ("Broken link ... VARREF"). AstMemberSel is
// class-handle member access only (packed-struct selects use AstStructSel and options
// use AstCoverOption), so scanning the value/iff expression will not flag supported
// coverpoints.
const auto scanHandleDeref = [&](AstNode* rootp) {
if (!rootp) return;
rootp->foreach([&](AstMemberSel* selp) {
if (!offenderp) offenderp = selp;
});
};
for (AstCoverpoint* cpp : m_coverpoints) {
scanHandleDeref(cpp->exprp());
scanHandleDeref(cpp->iffp());
}
return offenderp;
}
@ -1802,15 +1822,20 @@ class FunctionalCoverageVisitor final : public VNVisitor {
iterateChildren(nodep);
// Option B safety net for embedded covergroups: if a coverpoint/iff/cross
// references a member of the enclosing class, lowering would emit uncompilable
// C++ (no handle to the enclosing instance). Skip this covergroup with a clean
// warning rather than crashing the C++ compile. (Full support - an enclosing
// back-pointer - is the planned follow-up.)
if (AstNode* const offenderp = findEnclosingMemberRef(nodep)) {
// references a member of the enclosing class (no handle to the enclosing
// instance), or dereferences a class-handle argument of a parameterized
// covergroup, lowering would emit uncompilable C++ or crash V3Broken with a
// dangling VarRef. Skip this covergroup with a clean warning rather than
// failing. (Full support - an enclosing back-pointer and handle-argument
// lowering - is the planned follow-up.)
if (AstNode* const offenderp = findUnsupportedCoverpointRef(nodep)) {
const bool viaHandle = VN_IS(offenderp, MemberSel);
offenderp->v3warn(COVERIGN,
"Unsupported: 'covergroup' coverpoint referencing enclosing "
"class member; ignoring covergroup "
<< nodep->prettyNameQ());
"Unsupported: 'covergroup' coverpoint "
<< (viaHandle ? "dereferencing a class handle member "
"(parameterized covergroup)"
: "referencing enclosing class member")
<< "; ignoring covergroup " << nodep->prettyNameQ());
for (AstCoverpoint* cpp : m_coverpoints) {
VL_DO_DANGLING(pushDeletep(cpp->unlinkFrBack()), cpp);
}

8
test_regress/t/t_covergroup_embedded_unsup.out
View File

@ -1,7 +1,11 @@
%Warning-COVERIGN: t/t_covergroup_embedded_unsup.v:27:34: Unsupported: 'covergroup' coverpoint referencing enclosing class member; ignoring covergroup '__vlAnonCG_cov_trans'
%Warning-COVERIGN: t/t_covergroup_embedded_unsup.v:31:34: Unsupported: 'covergroup' coverpoint referencing enclosing class member; ignoring covergroup '__vlAnonCG_cov_trans'
: ... note: In instance 't'
27 | trans_start_addr: coverpoint trans_collected.addr {option.auto_bin_max = 16;}
31 | trans_start_addr: coverpoint trans_collected.addr {option.auto_bin_max = 16;}
| ^~~~~~~~~~~~~~~
... For warning description see https://verilator.org/warn/COVERIGN?v=latest
... Use "/* verilator lint_off COVERIGN */" and lint_on around source to disable this message.
%Warning-COVERIGN: t/t_covergroup_embedded_unsup.v:54:23: Unsupported: 'covergroup' coverpoint dereferencing a class handle member (parameterized covergroup); ignoring covergroup '__vlAnonCG_cov_param'
: ... note: In instance 't'
54 | cp: coverpoint st.test;
| ^~~~
%Error: Exiting due to

42
test_regress/t/t_covergroup_embedded_unsup.v
View File

@ -5,13 +5,17 @@
// SPDX-FileCopyrightText: 2026 Wilson Snyder
// SPDX-License-Identifier: CC0-1.0
// Test the graceful-degradation safety net for embedded covergroups (the dominant
// UVM pattern: a covergroup declared inside a class whose coverpoints reference the
// enclosing object's members). Such a covergroup is lowered into a sibling class
// with no handle to the enclosing instance, so emitting it would produce
// uncompilable C++ ("invalid use of non-static data member"). Until the enclosing
// back-pointer feature exists, Verilator must emit a clean COVERIGN warning and skip
// lowering the covergroup, rather than crashing the C++ compile.
// Test the graceful-degradation safety net for covergroups that cannot yet be lowered.
// Two unsupported shapes must degrade to a clean COVERIGN warning (rather than emitting
// uncompilable C++ or crashing) until full support exists:
// 1. Embedded covergroup (the dominant UVM pattern): coverpoints reference members of
// the enclosing object. The covergroup is lowered into a sibling class with no
// handle to the enclosing instance, so emitting it would produce uncompilable C++
// ("invalid use of non-static data member").
// 2. Parameterized covergroup: a coverpoint dereferences a class-handle argument
// ('coverpoint st.test'). The lowered class cannot resolve the handle argument, so
// lowering leaves a dangling VarRef and aborts in V3Broken ("Broken link ... VARREF").
// See https://github.com/verilator/verilator/issues/7853
class ubus_transfer;
bit [15:0] addr;
@ -35,10 +39,34 @@ class ubus_master_monitor;
endfunction
endclass
class coverage_state;
bit [3:0] test;
bit [3:0] test2;
endclass
class parameterized_monitor;
coverage_state cs;
// Parameterized covergroup: the coverpoints dereference the class-handle argument 'st'.
// Two handle-dereferencing coverpoints ensure the safety net reports only the first
// offender (a second AstMemberSel is seen with the offender already latched).
covergroup cov_param(coverage_state st);
cp: coverpoint st.test;
cp2: coverpoint st.test2;
endgroup
function new();
cs = new;
cov_param = new(cs);
endfunction
endclass
module t;
ubus_master_monitor m;
parameterized_monitor p;
initial begin
m = new;
p = new;
$write("*-* All Finished *-*\n");
$finish;
end