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Optimize Dfg synthesis of simple continuous assignments (#8286)

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This commit is contained in:
Geza Lore
2026-09-05 13:07:53 -04:00
committed by GitHub
parent bcf613c4fe
commit f2fe2b6f2e
1 changed files with 2 additions and 9 deletions
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src/V3DfgSynthesize.cpp
+2 -9
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@@ -268,7 +268,7 @@ class AstToDfgConverter final : public VNVisitor {
};
// Simplify the LHS, to get rid of things like SEL(CONCAT(_, _), _)
lhsp = VN_AS(V3Const::constifyExpensiveEdit(lhsp), NodeExpr);
if (!VN_IS(lhsp, VarRef)) lhsp = VN_AS(V3Const::constifyExpensiveEdit(lhsp), NodeExpr);
// Assigning compound expressions to a concatenated LHS requires a temporary
// to avoid multiple use of the expression
@@ -1593,11 +1593,6 @@ class AstToDfgSynthesize final {
bool synthesizeAssignW(AstAssignW* nodep) {
++m_ctx.m_synt.inputAssign;
// Construct an equivalent AstAssign
AstNodeExpr* const lhsp = nodep->lhsp()->cloneTree(false);
AstNodeExpr* const rhsp = nodep->rhsp()->cloneTree(false);
AstAssign* const assignp = new AstAssign{nodep->fileline(), lhsp, rhsp};
// The input and output symbol tables
SymTab iSymTab;
SymTab oSymTab;
@@ -1607,10 +1602,8 @@ class AstToDfgSynthesize final {
// Synthesize as if it was in a single CfgBlock CFG
DfgVertex* condp = nullptr;
const bool success = synthesizeBasicBlock(oSymTab, condp, {assignp}, iSymTab);
const bool success = synthesizeBasicBlock(oSymTab, condp, {nodep}, iSymTab);
UASSERT_OBJ(!condp, nodep, "Conditional AstAssignW ???");
// Delete auxiliary AstAssign
VL_DO_DANGLING(assignp->deleteTree(), assignp);
if (!success) return false;
// Check exernal writes are observed correctly