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Optimize n*powers of 2. (For parameterized DDR model)

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git-svn-id: file://localhost/svn/verilator/trunk/verilator@775 77ca24e4-aefa-0310-84f0-b9a241c72d87
This commit is contained in:
Wilson Snyder
2006-09-01 16:53:14 +00:00
parent 6f48185a1f
commit 749fdaae31
5 changed files with 56 additions and 11 deletions
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src/V3Const.cpp
+30 -2
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@@ -87,6 +87,10 @@ private:
return (nodep->castConst()
&& !nodep->castConst()->num().isFourState());
}
bool operandIsPowTwo(AstNode* nodep) {
if (!operandIsTwostate(nodep)) return false;
return (1==nodep->castConst()->num().countOnes());
}
bool operandShiftOp(AstNodeBiop* nodep) {
if (!nodep->rhsp()->castConst()) return false;
AstNodeBiop* lhsp = nodep->lhsp()->castNodeBiop();
@@ -317,6 +321,24 @@ private:
newp->lhsp()->widthSignedFrom(nodep);
nodep->replaceWith(newp); nodep->deleteTree(); nodep=NULL;
}
void replaceMulShift (AstMul* nodep) { // Mul, but not MulS as not simple shift
UINFO(5,"MUL(2^n,b)->SHIFTL(b,n) "<<nodep<<endl);
int amount = nodep->lhsp()->castConst()->num().mostSetBitP1()-1; // 2^n->n+1
AstNode* opp = nodep->rhsp()->unlinkFrBack();
AstShiftL* newp = new AstShiftL(nodep->fileline(),
opp, new AstConst(nodep->fileline(), amount));
newp->widthSignedFrom(nodep);
nodep->replaceWith(newp); nodep->deleteTree(); nodep=NULL;
}
void replaceDivShift (AstDiv* nodep) { // Mul, but not MulS as not simple shift
UINFO(5,"DIV(b,2^n)->SHIFTR(b,n) "<<nodep<<endl);
int amount = nodep->rhsp()->castConst()->num().mostSetBitP1()-1; // 2^n->n+1
AstNode* opp = nodep->lhsp()->unlinkFrBack();
AstShiftR* newp = new AstShiftR(nodep->fileline(),
opp, new AstConst(nodep->fileline(), amount));
newp->widthSignedFrom(nodep);
nodep->replaceWith(newp); nodep->deleteTree(); nodep=NULL;
}
void replaceShiftOp (AstNodeBiop* nodep) {
UINFO(5,"SHIFT(AND(a,b),CONST)->AND(SHIFT(a,CONST),SHIFT(b,CONST)) "<<nodep<<endl);
AstNRelinker handle;
@@ -970,8 +992,14 @@ private:
TREEOP("AstOr {$lhsp, $rhsp.isAllOnes}", "replaceWRhs(nodep)"); //->allOnes
TREEOP("AstLogOr {$lhsp, $rhsp.isNeqZero}", "replaceNum(nodep,1)");
TREEOP("AstXor {$lhsp.isAllOnes, $rhsp}", "AstNot{$rhsp}");
TREEOP("AstPow {operandIsTwo($lhsp), $rhsp}","replacePowShift(nodep)"); // 2**a == 1<<a
TREEOP("AstPowS {operandIsTwo($lhsp), $rhsp}","replacePowShift(nodep)"); // 2**a == 1<<a
TREEOP("AstMul {$lhsp.isOne, $rhsp}", "replaceWRhs(nodep)");
TREEOP("AstMulS {$lhsp.isOne, $rhsp}", "replaceWRhs(nodep)");
TREEOP("AstDiv {$lhsp, $rhsp.isOne}", "replaceWLhs(nodep)");
TREEOP("AstDivS {$lhsp, $rhsp.isOne}", "replaceWLhs(nodep)");
TREEOP("AstMul {operandIsPowTwo($lhsp), $rhsp}", "replaceMulShift(nodep)"); // a*2^n -> a<<n
TREEOP("AstDiv {$lhsp, operandIsPowTwo($rhsp)}", "replaceDivShift(nodep)"); // a/2^n -> a>>n
TREEOP("AstPow {operandIsTwo($lhsp), $rhsp}", "replacePowShift(nodep)"); // 2**a == 1<<a
TREEOP("AstPowS {operandIsTwo($lhsp), $rhsp}", "replacePowShift(nodep)"); // 2**a == 1<<a
// Trinary ops
// Note V3Case::Sel requires Cond to always be conditionally executed in C to prevent core dump!
TREEOP("AstNodeCond{$condp.isZero, $expr1p, $expr2p}", "replaceWChild(nodep,$expr2p)");