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Internals: Make the constant pool a regular package (#8512)

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The constant pool is now an ordinary package, created with the netlist
and instantiated under $root like any other package, and most special
handling has been removed, including AstConstPool. Lookups go through
V3ConstPool, which has a singleton instance owned by V3Global. Static
methods on V3Common form the public interfce to add/find constant pool
entries.

With that, the constant pool is usable at any stage during compilation,
so enum and dimension tables created by V3Width, and enum value tables
created by V3Randomize now also live in the constant pool instead of
$unit, so identical tables are shared.

Associative array constants are handled separately from unpacked
tables, which used to be broken but unused.

Emitted constant pool variables use direct initialization, and
`constinit` with C++20 where the type allows it. This ensures we don't
change a run-time in a way that would result in unintended code size
increase.

-fno-merge-const-pool, which was introduced years ago but never prompted
a bug report is deprecated and has no effect.

This is also prep for future work.
This commit is contained in:
Geza Lore
2026-09-27 13:25:41 +01:00
committed by GitHub
parent d234caafc1
commit 348b9b6209
68 changed files with 1239 additions and 930 deletions
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src/V3Randomize.cpp
+16 -21
View File
@@ -37,6 +37,7 @@
#include "V3Ast.h"
#include "V3Const.h"
#include "V3ConstPool.h"
#include "V3Error.h"
#include "V3FileLine.h"
#include "V3Global.h"
@@ -3657,7 +3658,7 @@ class RandomizeVisitor final : public VNVisitor {
// AstClass::user1() -> bool. Set true to indicate needs randomize processing
// AstVar::user2p() -> AstNodeModule*. Pointer to containing module
// AstNodeFTask::user2p() -> AstNodeModule*. Pointer to containing module
// AstEnumDType::user2() -> AstVar*. Pointer to table with enum values
// AstEnumDType::user2() -> AstVarRef*. Reference to table with enum values, to clone
// AstConstraint::user2p() -> AstTask*. Pointer to constraint setup procedure
// AstClass::user2p() -> AstVar*. Rand mode state variable
// AstVar::user3() -> bool. Handled in constraints
@@ -3686,7 +3687,6 @@ class RandomizeVisitor final : public VNVisitor {
AstNodeFTask* m_ftaskp = nullptr; // Current function/task
AstNodeStmt* m_stmtp = nullptr; // Current statement
AstDynArrayDType* m_dynarrayDtp = nullptr; // Dynamic array type (for rand mode)
size_t m_enumValueTabCount = 0; // Number of tables with enum values created
int m_randCaseNum = 0; // Randcase number within a module for var naming
int m_distNum = 0; // Dist bucket variable counter within a module for var naming
std::map<std::string, AstCDType*> m_randcDtypes; // RandC data type deduplication
@@ -4197,23 +4197,16 @@ class RandomizeVisitor final : public VNVisitor {
}
return stmtp;
}
AstVar* enumValueTabp(AstEnumDType* const nodep) {
if (nodep->user2p()) return VN_AS(nodep->user2p(), Var);
UINFO(9, "Construct Venumvaltab " << nodep);
AstVarRef* enumValueTabRefp(AstEnumDType* const nodep) {
// Return a reference to a constant table of the values of the given enum. The reference
// is cached, so the table is built only once.
if (nodep->user2p()) return VN_AS(nodep->user2p(), VarRef)->cloneTree(false);
UINFO(9, "Construct enum value table " << nodep);
AstNodeArrayDType* const vardtypep = new AstUnpackArrayDType{
nodep->fileline(), nodep->dtypep(),
new AstRange{nodep->fileline(), static_cast<int>(nodep->itemCount()), 0}};
AstInitArray* const initp = new AstInitArray{nodep->fileline(), vardtypep, nullptr};
new AstRange{nodep->fileline(), static_cast<int>(nodep->itemCount()) - 1, 0}};
v3Global.rootp()->typeTablep()->addTypesp(vardtypep);
AstVar* const varp
= new AstVar{nodep->fileline(), VVarType::MODULETEMP,
"__Venumvaltab_" + cvtToStr(m_enumValueTabCount++), vardtypep};
varp->isConst(true);
varp->isStatic(true);
varp->valuep(initp);
// Add to root, as don't know module we are in, and aids later structure sharing
v3Global.rootp()->dollarUnitPkgp()->addStmtsp(varp);
AstInitArray* const initp = new AstInitArray{nodep->fileline(), vardtypep, nullptr};
UASSERT_OBJ(nodep->itemsp(), nodep, "Enum without items");
for (AstEnumItem* itemp = nodep->itemsp(); itemp;
itemp = VN_AS(itemp->nextp(), EnumItem)) {
@@ -4221,8 +4214,12 @@ class RandomizeVisitor final : public VNVisitor {
UASSERT_OBJ(vconstp, nodep, "Enum item without constified value");
initp->addValuep(vconstp->cloneTree(false));
}
nodep->user2p(varp);
return varp;
// Share identical tables via the constant pool
AstVarRef* const refp = V3ConstPool::findTable(initp);
VL_DO_DANGLING(initp->deleteTree(), initp); // V3ConstPool::findTable clones it
pushDeletep(refp); // Deleted with the visitor - always cloned
nodep->user2p(refp);
return refp->cloneTree(false);
}
AstCDType* findVlRandCDType(FileLine* const fl, uint64_t items) {
@@ -4382,9 +4379,7 @@ class RandomizeVisitor final : public VNVisitor {
if (AstEnumDType* const enumDtp = VN_CAST(memberp ? memberp->subDTypep()->subDTypep()
: exprp->dtypep()->subDTypep(),
EnumDType)) {
AstVarRef* const tabRefp
= new AstVarRef{fl, enumValueTabp(enumDtp), VAccess::READ};
tabRefp->classOrPackagep(v3Global.rootp()->dollarUnitPkgp());
AstVarRef* const tabRefp = enumValueTabRefp(enumDtp);
AstNodeExpr* const randp
= newRandValue(fl, randcVarp, exprp->findBasicDType(VBasicDTypeKwd::UINT32));
AstNodeExpr* const moddivp = new AstModDiv{