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Fix shift-right optmiization, bug763.

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This commit is contained in:
Wilson Snyder
2014-05-10 16:38:20 -04:00
parent 1f56312132
commit 6ce2a52c5f
3 changed files with 15 additions and 2 deletions
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src/V3Const.cpp
+8 -2
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@@ -728,9 +728,15 @@ private:
AstNode* ap = lhsp->lhsp()->unlinkFrBack();
AstNode* shift1p = lhsp->rhsp()->unlinkFrBack();
AstNode* shift2p = nodep->rhsp()->unlinkFrBack();
// Shift1p and shift2p may have different sizes, both are self-determined so sum with infinite width
if (nodep->type()==lhsp->type()) {
int shift1 = shift1p->castConst()->toUInt();
int shift2 = shift2p->castConst()->toUInt();
int newshift = shift1+shift2;
shift1p->deleteTree(); shift1p=NULL;
shift2p->deleteTree(); shift2p=NULL;
nodep->lhsp(ap);
nodep->rhsp(new AstAdd(nodep->fileline(), shift1p, shift2p));
nodep->rhsp(new AstConst(nodep->fileline(), newshift));
nodep->accept(*this); // Further reduce, either node may have more reductions.
} else {
// We know shift amounts are constant, but might be a mixed left/right shift
@@ -738,7 +744,7 @@ private:
int shift2 = shift2p->castConst()->toUInt(); if (nodep->castShiftR()) shift2=-shift2;
int newshift = shift1+shift2;
shift1p->deleteTree(); shift1p=NULL;
shift2p->deleteTree(); shift1p=NULL;
shift2p->deleteTree(); shift2p=NULL;
AstNode* newp;
V3Number mask1 (nodep->fileline(), nodep->width());
V3Number ones (nodep->fileline(), nodep->width());