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Do not use function locals in SenExprBuilder (#5822) 

Function locals are not safe here because we might need to split up
the generated function. V3Localize can fix them later if safe.
This commit is contained in:
Geza Lore 2025-03-02 16:13:59 +00:00 committed by GitHub
parent bab949a468
commit 0133bc6b09
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GPG Key ID: B5690EEEBB952194
5 changed files with 24 additions and 51 deletions
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8
src/V3Sched.cpp
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@ -752,14 +752,6 @@ const TriggerKit createTriggers(AstNetlist* netlistp, AstCFunc* const initFuncp,
funcp->stmtsp()->addHereThisAsNext(nodep);
}
}
const auto& locals = senExprBuilder.getAndClearLocals();
if (!locals.empty()) {
UASSERT_OBJ(funcp->stmtsp(), funcp,
"No statements in trigger eval function, but there are locals");
for (AstVar* const nodep : vlstd::reverse_view(locals)) {
funcp->stmtsp()->addHereThisAsNext(nodep);
}
}
// Add the initialization statements
if (initialTrigsp) {

55
src/V3SenExprBuilder.h
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@ -31,7 +31,6 @@ class SenExprBuilder final {
// STATE
AstScope* const m_scopep; // The scope
std::vector<AstVar*> m_locals; // Trigger eval local variables
std::vector<AstNodeStmt*> m_inits; // Initialization statements for previous values
std::vector<AstNodeStmt*> m_preUpdates; // Pre update assignments
std::vector<AstNodeStmt*> m_postUpdates; // Post update assignments
@ -64,6 +63,21 @@ class SenExprBuilder final {
}
// METHODS
AstVarScope* crateTemp(AstNodeExpr* exprp) {
// For readability, use the scoped signal name if the trigger is a simple AstVarRef
string name;
if (AstVarRef* const refp = VN_CAST(exprp, VarRef)) {
AstVarScope* const vscp = refp->varScopep();
name = "__" + vscp->scopep()->nameDotless() + "__" + vscp->varp()->name();
name = m_prevNames.get(name);
} else {
name = m_prevNames.get(exprp);
}
AstVarScope* const vscp = m_scopep->createTemp(name, exprp->dtypep());
vscp->varp()->isInternal(true);
return vscp;
}
AstNodeExpr* getCurr(AstNodeExpr* exprp) {
// For simple expressions like varrefs or selects, just use them directly
if (isSimpleExpr(exprp)) return exprp->cloneTree(false);
@ -71,15 +85,7 @@ class SenExprBuilder final {
// Create the 'current value' variable
FileLine* const flp = exprp->fileline();
auto result = m_curr.emplace(*exprp, nullptr);
if (result.second) {
AstVar* const varp
= new AstVar{flp, VVarType::BLOCKTEMP, m_currNames.get(exprp), exprp->dtypep()};
varp->funcLocal(true);
m_locals.push_back(varp);
AstVarScope* vscp = new AstVarScope{flp, m_scopep, varp};
m_scopep->addVarsp(vscp);
result.first->second = vscp;
}
if (result.second) result.first->second = crateTemp(exprp);
AstVarScope* const currp = result.first->second;
// Add pre update if it does not exist yet in this round
@ -98,28 +104,8 @@ class SenExprBuilder final {
// Create the 'previous value' variable
const auto pair = m_prev.emplace(*scopeExprp, nullptr);
if (pair.second) {
AstVarScope* prevp;
if (m_scopep->isTop()) {
// For readability, use the scoped signal name if the trigger is a simple AstVarRef
string name;
if (AstVarRef* const refp = VN_CAST(exprp, VarRef)) {
AstVarScope* const vscp = refp->varScopep();
name = "__" + vscp->scopep()->nameDotless() + "__" + vscp->varp()->name();
name = m_prevNames.get(name);
} else {
name = m_prevNames.get(exprp);
}
prevp = m_scopep->createTemp(name, exprp->dtypep());
} else {
AstVar* const varp = new AstVar{flp, VVarType::BLOCKTEMP, m_prevNames.get(exprp),
exprp->dtypep()};
varp->funcLocal(true);
m_locals.push_back(varp);
prevp = new AstVarScope{flp, m_scopep, varp};
m_scopep->addVarsp(prevp);
}
AstVarScope* const prevp = crateTemp(exprp);
pair.first->second = prevp;
// Add the initializer init
AstAssign* const initp = new AstAssign{flp, new AstVarRef{flp, prevp, VAccess::WRITE},
exprp->cloneTree(false)};
@ -231,13 +217,6 @@ public:
std::vector<AstNodeStmt*> getAndClearInits() { return std::move(m_inits); }
std::vector<AstVar*> getAndClearLocals() {
// With m_locals empty, m_prev and m_curr are no longer valid
m_prev.clear();
m_curr.clear();
return std::move(m_locals);
}
std::vector<AstNodeStmt*> getAndClearPreUpdates() {
m_hasPreUpdate.clear();
return std::move(m_preUpdates);

5
src/V3Timing.cpp
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@ -933,10 +933,7 @@ class TimingControlVisitor final : public VNVisitor {
UASSERT_OBJ(m_senExprBuilderp, nodep, "No SenExprBuilder for this scope");
auto* const assignp = new AstAssign{flp, new AstVarRef{flp, trigvscp, VAccess::WRITE},
m_senExprBuilderp->build(sensesp).first};
// Put all the locals and inits before the trigger eval loop
for (AstVar* const varp : m_senExprBuilderp->getAndClearLocals()) {
nodep->addHereThisAsNext(varp);
}
// Put all and inits before the trigger eval loop
for (AstNodeStmt* const stmtp : m_senExprBuilderp->getAndClearInits()) {
nodep->addHereThisAsNext(stmtp);
}

5
test_regress/t/t_flag_csplit.v
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@ -53,4 +53,9 @@ module sub (input clk, input [31:0] i, output [31:0] z);
z_tmp <= i+1+$c("0"); // $c so doesn't optimize away
assign z = z_tmp;
always @(posedge z_tmp == 32'b11) begin
$display("%m z_tmp[0]: %d", z_tmp);
end
endmodule

2
test_regress/t/t_flag_csplit_groups.py
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@ -124,7 +124,7 @@ test.file_grep_not(test.obj_dir + "/" + test.vm_prefix + "_classes.mk", "vm_clas
test.file_grep_not(test.obj_dir + "/" + test.vm_prefix + "_classes.mk", "vm_classes_2")
# Check combine count
test.file_grep(test.stats, r'Node count, CFILE + (\d+)', (191 if test.vltmt else 173))
test.file_grep(test.stats, r'Node count, CFILE + (\d+)', (232 if test.vltmt else 212))
test.file_grep(test.stats, r'Makefile targets, VM_CLASSES_FAST + (\d+)', 2)
test.file_grep(test.stats, r'Makefile targets, VM_CLASSES_SLOW + (\d+)', 2)