internal static bool ReplacePushPopPattern(BlockStatement b, IMetadataHost host) {
Contract.Requires(b != null);
Contract.Requires(host != null);
bool replacedPattern = false;
var statements = b.Statements;
for (int i = 0; i < statements.Count-1; i++) {
//First identify count consecutive push statements
int count = 0;
while (i+count < statements.Count-1 && statements[i+count] is PushStatement) count++;
if (count == 0) continue;
Contract.Assert(i+count < statements.Count);
Contract.Assert(count < statements.Count);
for (int j = 0; j < count; j++) {
Contract.Assume(statements[i+j] is PushStatement);
if (((PushStatement)statements[i+j]).ValueToPush is DupValue) goto nextIteration;
}
Contract.Assert(i >= 0);
Contract.Assert(i < statements.Count-1);
//If any of the push statements (other than the first one) contains pop expressions, replace them with the corresponding push values and remove the pushes.
int pushcount = 1; //the number of push statements that are eligble for removal at this point.
for (int j = i + 1; j < i + count; j++) {
Contract.Assume(j < statements.Count); //because i+count < statements.Count for the initial value of count and count just decreases
Contract.Assume(j >= 0); //because i >= 0 and j never decreases to less than i
Contract.Assume(statements[j] is PushStatement); //because i < j < i+count and i..i+count-1 are all push statements
PushStatement st = (PushStatement)statements[j];
PopCounter pcc = new PopCounter();
pcc.Traverse(st.ValueToPush);
int numberOfPushesToRemove = pushcount;
if (pcc.count > 0) {
if (pcc.count < numberOfPushesToRemove) numberOfPushesToRemove = pcc.count;
int firstPushToRemove = j - numberOfPushesToRemove;
PopReplacer prr = new PopReplacer(host, statements, firstPushToRemove, pcc.count-numberOfPushesToRemove);
st.ValueToPush = prr.Rewrite(st.ValueToPush);
statements.RemoveRange(firstPushToRemove, numberOfPushesToRemove);
if (pcc.count > numberOfPushesToRemove) return true; //We've consumed all of the pushes and we're done.
count -= numberOfPushesToRemove; //Fewer pushes now remain
pushcount -= numberOfPushesToRemove; //Likewise fewer eligible pushes remain
//Start over again at firstPushToRemove, which now indexes the first statement not yet considered.
j = firstPushToRemove-1;
continue;
}
pushcount++;
}
Contract.Assume(count >= 0);
Contract.Assume(i+count < statements.Count);
var nextStatement = statements[i + count];
Contract.Assume(nextStatement != null);
if (!(nextStatement is IExpressionStatement || nextStatement is IPushStatement || nextStatement is IReturnStatement || nextStatement is IThrowStatement)) continue;
PopCounter pc = new PopCounter();
pc.Traverse(nextStatement);
if (pc.count == 0) continue;
if (pc.count < count) {
i += count-pc.count; //adjust i to point to the first push statement to remove because of subsequent pops.
count = pc.count;
}
Contract.Assume(i < statements.Count);
PopReplacer pr = new PopReplacer(host, statements, i, pc.count-count);
pr.Rewrite(nextStatement);
var s = nextStatement as Statement;
if (s != null)
s.Locations.AddRange(statements[i].Locations);
Contract.Assume(count >= 0);
Contract.Assert(i+count < statements.Count);
statements.RemoveRange(i, count);
replacedPattern = true;
nextIteration: ;
}
return replacedPattern;
}
private void ReplacePushPopPattern(List <IStatement> statements, int i)
{
if (i > statements.Count - 2)
{
return;
}
//First identify count consecutive push statements
int count = 0;
while (i + count < statements.Count - 1 && statements[i + count] is PushStatement)
{
count++;
}
while (i > 1 && statements[i - 1] is PushStatement)
{
i--; count++;
}
if (count == 0)
{
return;
}
for (int j = 0; j < count; j++)
{
if (((PushStatement)statements[j + i]).ValueToPush is Dup)
{
return;
}
}
//If any of the push statements (other than the first one) contains pop expressions, replace them with the corresponding push values and remove the pushes.
int pushcount = 1; //the number of push statements that are eligble for removal at this point.
for (int j = i + 1; j < i + count; j++)
{
PushStatement st = (PushStatement)statements[j];
PopCounter pcc = new PopCounter();
new CodeTraverser()
{
PreorderVisitor = pcc
}.Traverse(st.ValueToPush);
int numberOfPushesToRemove = pushcount;
if (pcc.count > 0)
{
if (pcc.count < numberOfPushesToRemove)
{
numberOfPushesToRemove = pcc.count;
}
int firstPushToRemove = j - numberOfPushesToRemove;
PopReplacer prr = new PopReplacer(this.sourceMethodBody.host, statements, firstPushToRemove, pcc.count - numberOfPushesToRemove);
st.ValueToPush = prr.Visit(st.ValueToPush);
statements.RemoveRange(firstPushToRemove, numberOfPushesToRemove);
j = j - pcc.count;
count = count - pcc.count;
pushcount = pushcount - pcc.count;
}
pushcount++;
}
//If the next statement is an expression statement that pops some of the just pushed values, replace those pops with the pushed values and remove the pushes.
ExpressionStatement /*?*/ expressionStatement = statements[i + count] as ExpressionStatement;
if (expressionStatement == null)
{
return;
}
PopCounter pc = new PopCounter();
new CodeTraverser()
{
PreorderVisitor = pc
}.Traverse(expressionStatement.Expression);
if (pc.count == 0)
{
return;
}
if (pc.count < count)
{
i += count - pc.count; //adjust i to point to the first push statement to remove because of subsequent pops.
count = pc.count;
}
PopReplacer pr = new PopReplacer(this.sourceMethodBody.host, statements, i, pc.count - count);
expressionStatement.Expression = pr.Visit(expressionStatement.Expression);
expressionStatement.Locations.AddRange(statements[i].Locations);
statements.RemoveRange(i, count);
}
private void ReplacePushPopPattern(List<IStatement> statements, int i)
{
if (i > statements.Count - 2) return;
//First identify count consecutive push statements
int count = 0;
while (i+count < statements.Count-1 && statements[i+count] is PushStatement) count++;
while (i > 1 && statements[i-1] is PushStatement) { i--; count++; }
if (count == 0) return;
for (int j = 0; j < count; j++) {
if (((PushStatement)statements[j+i]).ValueToPush is Dup) return;
}
//If any of the push statements (other than the first one) contains pop expressions, replace them with the corresponding push values and remove the pushes.
int pushcount = 1; //the number of push statements that are eligble for removal at this point.
for (int j = i + 1; j < i + count; j++) {
PushStatement st = (PushStatement)statements[j];
PopCounter pcc = new PopCounter();
new CodeTraverser() { PreorderVisitor = pcc }.Traverse(st.ValueToPush);
int numberOfPushesToRemove = pushcount;
if (pcc.count > 0) {
if (pcc.count < numberOfPushesToRemove) numberOfPushesToRemove = pcc.count;
int firstPushToRemove = j - numberOfPushesToRemove;
PopReplacer prr = new PopReplacer(this.sourceMethodBody.host, statements, firstPushToRemove, pcc.count-numberOfPushesToRemove);
st.ValueToPush = prr.Visit(st.ValueToPush);
statements.RemoveRange(firstPushToRemove, numberOfPushesToRemove);
j = j - pcc.count;
count = count - pcc.count;
pushcount = pushcount - pcc.count;
}
pushcount++;
}
//If the next statement is an expression statement that pops some of the just pushed values, replace those pops with the pushed values and remove the pushes.
ExpressionStatement/*?*/ expressionStatement = statements[i + count] as ExpressionStatement;
if (expressionStatement == null) return;
PopCounter pc = new PopCounter();
new CodeTraverser() { PreorderVisitor = pc }.Traverse(expressionStatement.Expression);
if (pc.count == 0) return;
if (pc.count < count) {
i += count-pc.count; //adjust i to point to the first push statement to remove because of subsequent pops.
count = pc.count;
}
PopReplacer pr = new PopReplacer(this.sourceMethodBody.host, statements, i, pc.count-count);
expressionStatement.Expression = pr.Visit(expressionStatement.Expression);
statements.RemoveRange(i, count);
}