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Internals: Better prefetching for ~5%.

This commit is contained in:
Wilson Snyder 2017-09-16 07:55:48 -04:00
parent fee4aba9ec
commit f30d71b0c5
1 changed files with 5 additions and 1 deletions
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6
src/V3Ast.cpp
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@ -716,6 +716,7 @@ void AstNode::deleteTree() {
#ifdef VL_LEAK_CHECKS
void* AstNode::operator new(size_t size) {
// Optimization note: Aligning to cache line is a loss, due to lost packing
AstNode* objp = static_cast<AstNode*>(::operator new(size));
V3Broken::addNewed(objp);
return objp;
@ -734,6 +735,7 @@ void AstNode::operator delete(void* objp, size_t size) {
void AstNode::iterateChildren(AstNVisitor& v) {
// This is a very hot function
// Optimization note: Grabbing m_op#p->m_nextp is a net loss
ASTNODE_PREFETCH(m_op1p);
ASTNODE_PREFETCH(m_op2p);
ASTNODE_PREFETCH(m_op3p);
@ -766,11 +768,13 @@ void AstNode::iterateAndNext(AstNVisitor& v) {
#ifdef VL_DEBUG // Otherwise too hot of a function for debug
if (VL_UNLIKELY(nodep && !nodep->m_backp)) nodep->v3fatalSrc("iterateAndNext node has no back");
#endif
if (nodep) ASTNODE_PREFETCH(nodep->m_nextp);
while (nodep) { // effectively: if (!this) return; // Callers rely on this
if (nodep->m_nextp) ASTNODE_PREFETCH(nodep->m_nextp->m_nextp);
AstNode* niterp = nodep; // This address may get stomped via m_iterpp if the node is edited
ASTNODE_PREFETCH(nodep->m_nextp);
// Desirable check, but many places where multiple iterations are OK
//if (VL_UNLIKELY(niterp->m_iterpp)) niterp->v3fatalSrc("IterateAndNext under iterateAndNext may miss edits");
// Optimization note: Doing PREFETCH_RW on m_iterpp is a net even
// cppcheck-suppress nullPointer
niterp->m_iterpp = &niterp;
niterp->accept(v);