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Internals: Fix V3LifePost recording assignPre variables. 

Signed-off-by: Wilson Snyder <wsnyder@wsnyder.org>
This commit is contained in:
John Coiner 2018-02-28 06:57:08 -05:00 committed by Wilson Snyder
parent f0ba17a19b
commit 0a887c29f1
1 changed files with 26 additions and 11 deletions
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37
src/V3LifePost.cpp
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@ -147,23 +147,38 @@ private:
vscp->user2(m_sequence);
}
}
virtual void visit(AstAssignPre* nodep) {
// Do not record varrefs within assign pre.
//
// The pre-assignment into the dly var should not count as its
// first write; we only want to consider reads and writes that
// would still happen if the dly var were eliminated.
}
virtual void visit(AstAssignPost* nodep) {
if (AstVarRef* lhsp = VN_CAST(nodep->lhsp(), VarRef)) {
if (AstVarRef* rhsp = VN_CAST(nodep->rhsp(), VarRef)) {
// Scrunch these:
// __Vdly__q = __PVT__clk_clocks;
// ... {no reads or writes of __PVT__q after the first write to __Vdly__q}
// ... {no reads of __Vdly__q after the first write to __Vdly__q}
// __PVT__q = __Vdly__q;
// Scrunch these:
// X1: __Vdly__q = __PVT__clk_clocks;
// ... {no reads of __PVT__q after the first write to __Vdly__q}
// ... {no reads of __Vdly__q after the first write to __Vdly__q}
// X2: __PVT__q = __Vdly__q;
//
// Into just this:
// X1: __PVT__q = __PVT__clk_clocks;
// X2: (nothing)
UINFO(9," POST "<<nodep<<endl);
UINFO(9," lhs "<<lhsp<<endl);
UINFO(9," rhs "<<rhsp<<endl);
uint32_t firstWrite = rhsp->varScopep()->user1();
uint32_t lastRead = rhsp->varScopep()->user2();
uint32_t lastRead2 = lhsp->varScopep()->user2();
UINFO(9," first "<<firstWrite<<" last "<<lastRead<<" "<<lastRead2<<endl);
if (lastRead < firstWrite
&& lastRead2 < firstWrite) {
uint32_t firstDlyVarWrite = rhsp->varScopep()->user1();
uint32_t lastDlyVarRead = rhsp->varScopep()->user2();
uint32_t lastOrigVarRead = lhsp->varScopep()->user2();
UINFO(9," first_dly_w "<<firstDlyVarWrite
<<" last_dly_r "<<lastDlyVarRead
<<" last_orig_r "<<lastOrigVarRead<<endl);
if (lastDlyVarRead < firstDlyVarWrite
&& lastOrigVarRead < firstDlyVarWrite) {
UINFO(4," DELETE "<<nodep<<endl);
// Mark so LifePostElimVisitor will get it
rhsp->varScopep()->user4p(lhsp->varScopep());