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Optimize mask/and above conditionals.

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This commit is contained in:
Wilson Snyder
2019-11-10 13:17:29 -05:00
parent ce178ec987
commit 2b26ca2c07
4 changed files with 141 additions and 1 deletions
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src/V3Const.cpp
+26
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@@ -218,6 +218,31 @@ private:
else nodep->rhsp(cp);
return true;
}
bool matchAndCond(AstAnd* nodep) {
// Push down a AND into conditional, when one side of conditional is constant
// (otherwise we'd be trading one operation for two operations)
// V3Clean often makes this pattern, as it postpones the AND until
// as high as possible, which is usally the right choice, except for this.
AstNodeCond* condp = VN_CAST(nodep->rhsp(), NodeCond);
if (!condp) return false;
if (!VN_IS(condp->expr1p(), Const) && !VN_IS(condp->expr2p(), Const)) return false;
AstConst* maskp = VN_CAST(nodep->lhsp(), Const);
if (!maskp) return false;
UINFO(4, "AND(CONSTm, CONDcond(c, i, e))->CONDcond(c, AND(m,i), AND(m, e)) "<<nodep<<endl);
AstNodeCond* newp = (AstNodeCond*)condp->cloneType
(condp->condp()->unlinkFrBack(),
new AstAnd(nodep->fileline(),
maskp->cloneTree(false),
condp->expr1p()->unlinkFrBack()),
new AstAnd(nodep->fileline(),
maskp->cloneTree(false),
condp->expr2p()->unlinkFrBack()));
newp->dtypeFrom(nodep);
newp->expr1p()->dtypeFrom(nodep); // As And might have been to change widths
newp->expr2p()->dtypeFrom(nodep);
nodep->replaceWith(newp); nodep->deleteTree(); VL_DANGLING(nodep);
return true;
}
static bool operandShiftSame(const AstNode* nodep) {
const AstNodeBiop* np = VN_CAST_CONST(nodep, NodeBiop);
{
@@ -2442,6 +2467,7 @@ private:
TREEOPV("AstConcat{$lhsp.castSel, $rhsp.castSel, ifAdjacentSel(VN_CAST($lhsp,,Sel),,VN_CAST($rhsp,,Sel))}", "replaceConcatSel(nodep)");
TREEOPV("AstConcat{ifConcatMergeableBiop($lhsp), concatMergeable($lhsp,,$rhsp)}", "replaceConcatMerge(nodep)");
// Common two-level operations that can be simplified
TREEOP ("AstAnd {$lhsp.castConst,matchAndCond(nodep)}", "DONE");
TREEOP ("AstAnd {$lhsp.castOr, $rhsp.castOr, operandAndOrSame(nodep)}", "replaceAndOr(nodep)");
TREEOP ("AstOr {$lhsp.castAnd,$rhsp.castAnd,operandAndOrSame(nodep)}", "replaceAndOr(nodep)");
TREEOP ("AstOr {matchOrAndNot(nodep)}", "DONE");