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Eliminate assigned only variables

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git-svn-id: file://localhost/svn/verilator/trunk/verilator@797 77ca24e4-aefa-0310-84f0-b9a241c72d87
This commit is contained in:
Wilson Snyder
2006-09-26 17:05:08 +00:00
parent ba7b4f261a
commit ca4e3c1737
3 changed files with 67 additions and 6 deletions
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src/V3Life.cpp
+23 -3
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@@ -264,7 +264,8 @@ public:
class LifeVisitor : public AstNVisitor {
private:
// STATE
LifeState* m_statep; // Current state
LifeState* m_statep; // Current state
bool m_sideEffect; // Side effects discovered in assign RHS
//static int debug() { return 9; }
// LIFE MAP
@@ -289,7 +290,9 @@ private:
}
virtual void visit(AstNodeAssign* nodep, AstNUser*) {
// Collect any used variables first, as lhs may also be on rhs
// Similar code in V3Dead
vluint64_t lastEdit = AstNode::editCountGbl(); // When it was last edited
m_sideEffect = false;
nodep->rhsp()->iterateAndNext(*this);
if (lastEdit != AstNode::editCountGbl()) {
// We changed something, try to constant propagate, but don't delete the
@@ -297,7 +300,7 @@ private:
V3Const::constifyTree(nodep->rhsp());
}
// Has to be direct assignment without any EXTRACTing.
if (nodep->lhsp()->castVarRef()) {
if (nodep->lhsp()->castVarRef() && !m_sideEffect) {
AstVarScope* vscp = nodep->lhsp()->castVarRef()->varScopep();
if (!vscp) vscp->v3fatalSrc("Scope lost on variable");
m_lifep->simpleAssign(vscp, nodep);
@@ -373,6 +376,10 @@ private:
// Enter the function and trace it
nodep->funcp()->accept(*this);
}
virtual void visit(AstUCFunc* nodep, AstNUser*) {
m_sideEffect = true; // If appears on assign RHS, don't ever delete the assignment
nodep->iterateChildren(*this);
}
virtual void visit(AstVar*, AstNUser*) {} // Don't want varrefs under it
virtual void visit(AstNode* nodep, AstNUser*) {
@@ -381,9 +388,10 @@ private:
public:
// CONSTRUCTORS
LifeVisitor(AstCFunc* nodep, LifeState* statep) {
LifeVisitor(AstNode* nodep, LifeState* statep) {
UINFO(4," LifeVisitor on "<<nodep<<endl);
m_statep = statep;
m_sideEffect = false;
{
m_lifep = new LifeBlock (NULL, m_statep);
nodep->accept(*this);
@@ -409,6 +417,18 @@ private:
LifeVisitor visitor (nodep, m_statep);
}
}
virtual void visit(AstAlways* nodep, AstNUser*) {
// Usage model 2: Cleanup basic blocks
LifeVisitor visitor (nodep, m_statep);
}
virtual void visit(AstInitial* nodep, AstNUser*) {
// Usage model 2: Cleanup basic blocks
LifeVisitor visitor (nodep, m_statep);
}
virtual void visit(AstFinal* nodep, AstNUser*) {
// Usage model 2: Cleanup basic blocks
LifeVisitor visitor (nodep, m_statep);
}
virtual void visit(AstVar*, AstNUser*) {} // Accelerate
virtual void visit(AstNodeStmt*, AstNUser*) {} // Accelerate
virtual void visit(AstNodeMath*, AstNUser*) {} // Accelerate