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Fix removing if statement with side effect in condition (#3131).

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Wilson Snyder 2021-09-13 15:52:53 -04:00
parent 81fd3e4732
commit 08c8b0d7d6
4 changed files with 23 additions and 4 deletions
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1
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@ -14,6 +14,7 @@ Verilator 4.213 devel
* Include processor information in verilator_gantt data file.
* Fix verilator_profcfunc profile accounting (#3115).
* Fix display has no time units on class function (#3116). [Damien Pretet]
* Fix removing if statement with side effect in condition (#3131). [Alexander Grobman]
Verilator 4.212 2021-09-01

1
src/V3AstNodes.h
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@ -4436,6 +4436,7 @@ public:
virtual string emitC() override { V3ERROR_NA_RETURN(""); }
virtual bool isGateOptimizable() const override { return false; }
virtual bool isPredictOptimizable() const override { return false; }
virtual bool isPure() const override { return !outp(); }
virtual bool cleanOut() const override { return true; }
virtual bool same(const AstNode* samep) const override { return true; }
AstNode* searchp() const { return op1p(); } // op1 = Search expression

20
src/V3Const.cpp
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@ -1312,6 +1312,15 @@ private:
// but for now can disable en-mass until V3Purify takes effect.
return m_doShort || VN_IS(nodep, VarRef) || VN_IS(nodep, Const);
}
bool isTreePureRecurse(AstNode* nodep) {
// Should memoize this if call commonly
if (!nodep->isPure()) return false;
if (nodep->op1p() && !isTreePureRecurse(nodep->op1p())) return false;
if (nodep->op2p() && !isTreePureRecurse(nodep->op2p())) return false;
if (nodep->op3p() && !isTreePureRecurse(nodep->op3p())) return false;
if (nodep->op4p() && !isTreePureRecurse(nodep->op4p())) return false;
return true;
}
// Extraction checks
bool warnSelect(AstSel* nodep) {
@ -2783,10 +2792,13 @@ private:
}
VL_DO_DANGLING(nodep->deleteTree(), nodep);
} else if (!afterComment(nodep->ifsp()) && !afterComment(nodep->elsesp())) {
// Empty block, remove it
// Note if we support more C++ then there might be side
// effects in the condition itself
VL_DO_DANGLING(nodep->unlinkFrBack()->deleteTree(), nodep);
if (!isTreePureRecurse(nodep->condp())) {
// Condition has side effect - leave - perhaps in
// future simplify to remove all but side effect terms
} else {
// Empty block, remove it
VL_DO_DANGLING(nodep->unlinkFrBack()->deleteTree(), nodep);
}
} else if (!afterComment(nodep->ifsp())) {
UINFO(4, "IF({x}) nullptr {...} => IF(NOT{x}}: " << nodep << endl);
AstNode* condp = nodep->condp();

5
test_regress/t/t_sys_plusargs.v
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@ -103,6 +103,11 @@ module t;
$display("i='%d'",p_i);
if (p_i !== 32'd1234) $stop;
// bug3131 - really "if" side effect test
p_i = 0;
if ($value$plusargs("INT=%d", p_i)) ;
if (p_i !== 32'd1234) $stop;
$write("*-* All Finished *-*\n");
$finish;
end