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Optimize SUB/ADD together.

This commit is contained in:
Wilson Snyder 2014-11-09 18:33:54 -05:00
parent c5fd583b2c
commit 62eb247c1e
1 changed files with 11 additions and 0 deletions
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11
src/V3Const.cpp
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@ -173,6 +173,16 @@ private:
if (rnodep->width() != bnodep->width()) return false;
return rnodep->lhsp()->castConst();
}
static bool operandSubAdd(AstNode* nodep) {
// SUB( ADD(CONSTx,y), CONSTz) -> ADD(SUB(CONSTx,CONSTz), y)
AstNodeBiop* np = nodep->castNodeBiop();
AstNodeBiop* lp = np->lhsp()->castNodeBiop();
return (lp
&& lp->lhsp()->castConst()
&& np->rhsp()->castConst()
&& lp->width()==np->width());
}
static bool operandAndOrSame(AstNode* nodep) {
// OR( AND(VAL,x), AND(VAL,y)) -> AND(VAL,OR(x,y))
// OR( AND(x,VAL), AND(y,VAL)) -> AND(OR(x,y),VAL)
@ -2032,6 +2042,7 @@ private:
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), $rhsp}", "replacePowShift(nodep)"); // 2**a == 1<<a
TREEOP ("AstSub {$lhsp.castAdd, operandSubAdd(nodep)}", "AstAdd{AstSub{$lhsp->castAdd()->lhsp(),$rhsp}, $lhsp->castAdd()->rhsp()}"); // ((a+x)-y) -> (a+(x-y))
// Trinary ops
// Note V3Case::Sel requires Cond to always be conditionally executed in C to prevent core dump!
TREEOP ("AstNodeCond{$condp.isZero, $expr1p, $expr2p}", "replaceWChild(nodep,$expr2p)");