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Lifting zig and zag cases into common prefix to shorten splaysplit. a few percent faster.

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 Change: 184446
 ServerID: perforce.ravenbrook.com
This commit is contained in:
Richard Brooksby 2014-02-22 20:16:21 +00:00
parent 660c0821d6
commit 96be04cb42
1 changed files with 24 additions and 17 deletions
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41
mps/code/splay.c
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@ -250,7 +250,7 @@ static Compare SplaySplit(Tree *nodeReturn,
{
/* The sides structure avoids a boundary case in SplayLink* */
TreeStruct sides; /* rightTop and leftTop */
Tree node, leftLast, rightFirst;
Tree node, leftLast, rightFirst, leftPrev, rightNext;
Compare cmp;
AVERT(SplayTree, tree);
@ -279,30 +279,34 @@ static Compare SplaySplit(Tree *nodeReturn,
if (child == TreeEMPTY)
goto assemble;
rightNext = rightFirst;
SplayLinkRight(&node, &rightFirst); /* zig */
cmp = compare(child, key);
switch(cmp) {
default:
NOTREACHED;
/* defensive fall-through */
case CompareEQUAL: /* zig */
SplayLinkRight(&node, &rightFirst);
case CompareEQUAL:
goto assemble;
case CompareLESS: /* zig-zig */
if (TreeLeft(child) == TreeEMPTY) {
SplayLinkRight(&node, &rightFirst);
if (TreeLeft(child) == TreeEMPTY)
goto assemble;
}
TreeRotateRight(&node);
SplayLinkRight(&node, &rightFirst);
TreeSetLeft(rightFirst, TreeRight(node));
TreeSetRight(node, rightFirst);
TreeSetLeft(rightNext, node);
rightFirst = node;
node = TreeLeft(node);
TreeClearLeft(rightFirst); /* for AVER */
tree->updateNode(tree, TreeRight(rightFirst));
break;
case CompareGREATER: /* zig-zag */
SplayLinkRight(&node, &rightFirst);
if (TreeRight(child) == TreeEMPTY)
goto assemble;
leftPrev = leftLast;
SplayLinkLeft(&node, &leftLast);
break;
}
@ -313,28 +317,31 @@ static Compare SplaySplit(Tree *nodeReturn,
if (child == TreeEMPTY)
goto assemble;
leftPrev = leftLast;
SplayLinkLeft(&node, &leftLast); /* zag */
cmp = compare(child, key);
switch(cmp) {
default:
NOTREACHED;
/* defensive fall-through */
case CompareEQUAL: /* zag */
SplayLinkLeft(&node, &leftLast);
case CompareEQUAL:
goto assemble;
case CompareGREATER: /* zag-zag */
if (TreeRight(child) == TreeEMPTY) {
SplayLinkLeft(&node, &leftLast);
if (TreeRight(child) == TreeEMPTY)
goto assemble;
}
TreeRotateLeft(&node);
SplayLinkLeft(&node, &leftLast);
TreeSetRight(leftLast, TreeLeft(node));
TreeSetLeft(node, leftLast);
TreeSetRight(leftPrev, node);
leftLast = node;
node = TreeRight(node);
TreeClearRight(leftLast); /* for AVER */
tree->updateNode(tree, TreeLeft(leftLast));
break;
case CompareLESS: /* zag-zig */
SplayLinkLeft(&node, &leftLast);
if (TreeLeft(child) == TreeEMPTY)
goto assemble;
SplayLinkRight(&node, &rightFirst);