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Always split functions under '-split-functions=1' option. 

Summary:
Force the splitting of the function into hot/cold even when
the function fits into original slot.

This reduces BOLT optimization time by 50% without affecting
hhvm performance.

(cherry picked from FBD2973773)
This commit is contained in:
Maksim Panchenko 2016-02-22 16:49:26 -08:00
parent 73e9afe99c
commit 62da18d32a
2 changed files with 1 additions and 42 deletions
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33
bolt/RewriteInstance.cpp
View File

@ -472,18 +472,6 @@ void RewriteInstance::run() {
runOptimizationPasses();
emitFunctions();
if (opts::SplitFunctions && splitLargeFunctions()) {
// Emit again because now some functions have been split
outs() << "BOLT: split-functions: starting pass 2...\n";
reset();
discoverStorage();
readSymbolTable();
readSpecialSections();
disassembleFunctions();
runOptimizationPasses();
emitFunctions();
}
// Copy input file to output
std::error_code EC;
Out = llvm::make_unique<tool_output_file>(opts::OutputFilename, EC,
@ -838,8 +826,7 @@ void RewriteInstance::runOptimizationPasses() {
}
if (opts::ReorderBlocks != BinaryFunction::LT_NONE) {
bool ShouldSplit = ToSplit.find(BFI.first) != ToSplit.end();
BFI.second.modifyLayout(opts::ReorderBlocks, ShouldSplit);
BFI.second.modifyLayout(opts::ReorderBlocks, opts::SplitFunctions);
if (opts::PrintAll || opts::PrintReordered)
Function.print(errs(), "after reordering blocks");
}
@ -1225,24 +1212,6 @@ void RewriteInstance::emitFunctions() {
TempOut->keep();
}
bool RewriteInstance::splitLargeFunctions() {
bool Changed = false;
for (auto &BFI : BinaryFunctions) {
auto &Function = BFI.second;
// Ignore this function if we failed to map it to the output binary
if (Function.getImageAddress() == 0 || Function.getImageSize() == 0)
continue;
if (Function.getImageSize() <= Function.getMaxSize())
continue;
ToSplit.insert(BFI.first);
Changed = true;
}
return Changed;
}
void RewriteInstance::patchELF() {
auto ELF64LEFile = dyn_cast<ELF64LEObjectFile>(File);
if (!ELF64LEFile) {

10
bolt/RewriteInstance.h
View File

@ -127,13 +127,6 @@ public:
/// performing final relaxation.
void emitFunctions();
/// Check which functions became larger than their original version and
/// annotate function splitting information.
///
/// Returns true if any function was annotated, requiring us to perform a
/// second pass to emit those functions in two parts.
bool splitLargeFunctions();
/// Rewrite back all functions (hopefully optimized) that fit in the original
/// memory footprint for that function. If the function is now larger and does
/// not fit in the binary, reject it and preserve the original version of the
@ -213,9 +206,6 @@ private:
/// rewriting CFI info for these functions.
std::vector<uint64_t> FailedAddresses;
/// Keep track of which functions to split in a second pass.
std::set<uint64_t> ToSplit;
/// Total hotness score according to profiling data for this binary.
uint64_t TotalScore{0};