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[BOLT] Improved Jump-Distance Metric 

Summary:
Current existing Jump-Distance Metric (Previously named Call-Distance) will ignore some traversals.
This modified version adds those missing traversals back.

The correlation remains the same: around 97% correlation with CPU and
Cache Miss (which implies that even though some traversals are ignored,
it doesn't affect correlation that much.)

(cherry picked from FBD5369653)
This commit is contained in:
Bohan Ren 2017-07-04 15:59:29 -07:00 committed by Maksim Panchenko
parent 4ecd3856e9
commit 4d34471eeb
2 changed files with 15 additions and 10 deletions
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21
bolt/CalcCacheMetrics.cpp
View File

@ -50,10 +50,10 @@ getPositionMap(const BinaryFunction &Function) {
/// Initialize and return a vector of traversals for a given function and its
/// entry point
std::vector<Traversal> getTraversals(const BinaryFunction &Function,
BinaryBasicBlock *BB) {
BinaryBasicBlock *EntryBB) {
std::vector<Traversal> AllTraversals;
std::stack<std::pair<BinaryBasicBlock *, Traversal>> Stack;
Stack.push(std::make_pair(BB, Traversal()));
Stack.push(std::make_pair(EntryBB, Traversal()));
std::unordered_set<BinaryBasicBlock *> BBSet;
while (!Stack.empty()) {
@ -70,23 +70,28 @@ std::vector<Traversal> getTraversals(const BinaryFunction &Function,
continue;
}
uint64_t SuccTotalCount = 0;
bool HaveSuccCount = false;
// Calculate total edges count of successors
for (auto BI = CurrentBB->branch_info_begin();
BI != CurrentBB->branch_info_end(); ++BI) {
if (BI->Count != BinaryBasicBlock::COUNT_NO_PROFILE) {
SuccTotalCount += BI->Count;
if (BI->Count != BinaryBasicBlock::COUNT_NO_PROFILE && BI->Count > 0) {
HaveSuccCount = true;
break;
}
}
if (SuccTotalCount == 0) {
if (!HaveSuccCount) {
AllTraversals.push_back(PrevTraversal);
continue;
}
auto BI = CurrentBB->branch_info_begin();
for (auto *SuccBB : CurrentBB->successors()) {
if (BBSet.find(SuccBB) == BBSet.end() && BI->Count != 0 &&
BI->Count != BinaryBasicBlock::COUNT_NO_PROFILE) {
// If we have never seen SuccBB, or SuccBB indicates the
// end of traversal, SuccBB will be added into stack for
// further exploring.
if ((BBSet.find(SuccBB) == BBSet.end() && BI->Count != 0 &&
BI->Count != BinaryBasicBlock::COUNT_NO_PROFILE) ||
SuccBB->succ_empty()) {
Stack.push(std::make_pair(SuccBB, PrevTraversal));
}
++BI;

4
bolt/RewriteInstance.cpp
View File

@ -820,7 +820,7 @@ void RewriteInstance::run() {
}
if (opts::CalcCacheMetrics) {
outs() << "\nBOLT-INFO: After Optimization Call Graph Statistics: Call "
outs() << "\nBOLT-INFO: After Optimization CFG Graph Statistics: Jump "
"Distance \n\n";
CalcCacheMetrics::calcGraphDistance(BinaryFunctions);
}
@ -1874,7 +1874,7 @@ void RewriteInstance::disassembleFunctions() {
}
if (opts::CalcCacheMetrics) {
outs() << "\nBOLT-INFO: Before Optimization Call Graph Statistics: Call "
outs() << "\nBOLT-INFO: Before Optimization CFG Graph Statistics: Jump "
"Distance \n\n";
CalcCacheMetrics::calcGraphDistance(BinaryFunctions);
}