intel/llvm
1
0
Fork 0
mirror of https://github.com/intel/llvm.git synced 2026-01-21 20:53:29 +08:00
Code Issues Packages Projects Releases Wiki Activity

[BOLT] Fix double jump peephole, remove useless conditional branches.

Browse Source 
Summary:
I split some of this out from the jumptable diff since it fixes the
double jump peephole.

I've changed the pass manager so that UCE and peepholes are not called
after SCTC.  I've incorporated a call to the double jump fixer to SCTC
since it is needed to fix things up afterwards.

While working on fixing the double jump peephole I discovered a few
useless conditional branches that could be removed as well.  I highly
doubt that removing them will improve perf at all but it does seem
odd to leave in useless conditional branches.

There are also some minor logging improvements.

(cherry picked from FBD4751875)
This commit is contained in:
Bill Nell
2017-03-20 22:44:25 -07:00
committed by Maksim Panchenko
parent f7d32f7e7d
commit 6c5c65e3a3
7 changed files with 282 additions and 134 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
bolt/BinaryFunction.cpp
View File

@@ -322,10 +322,22 @@ std::pair<unsigned, uint64_t> BinaryFunction::eraseInvalidBBs() {
}
bool BinaryFunction::isForwardCall(const MCSymbol *CalleeSymbol) const {
// TODO: Once we start reordering functions this has to change. #15031238
// This function should work properly before and after function reordering.
// In order to accomplish this, we use the function index (if it is valid).
// If the function indices are not valid, we fall back to the original
// addresses. This should be ok because the functions without valid indices
// should have been ordered with a stable sort.
const auto *CalleeBF = BC.getFunctionForSymbol(CalleeSymbol);
if (CalleeBF) {
return CalleeBF->getAddress() > getAddress();
if (hasValidIndex() && CalleeBF->hasValidIndex()) {
return getIndex() < CalleeBF->getIndex();
} else if (hasValidIndex() && !CalleeBF->hasValidIndex()) {
return true;
} else if (!hasValidIndex() && CalleeBF->hasValidIndex()) {
return false;
} else {
return getAddress() < CalleeBF->getAddress();
}
} else {
// Absolute symbol.
auto const CalleeSI = BC.GlobalSymbols.find(CalleeSymbol->getName());
@@ -2888,6 +2900,9 @@ void BinaryFunction::fixBranches() {
} else {
MIA->replaceBranchTarget(*CondBranch, TSuccessor->getLabel(), Ctx);
}
if (TSuccessor == FSuccessor) {
BB->removeDuplicateConditionalSuccessor(CondBranch);
}
if (!NextBB || (NextBB != TSuccessor && NextBB != FSuccessor)) {
BB->addBranchInstruction(FSuccessor);
}