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[llvm-reduce] Use DenseSet instead of std::set (NFC). 

When reducing functions with very large basic blocks (~ almost 1 million
BBs), the majority of time is spent maintaining the order in the std::set
for the basic blocks to keep.

In those cases, DenseSet<> is much more efficient. Use it instead.
This commit is contained in:
Florian Hahn 2021-11-10 13:56:22 +00:00
parent 0609eb1b32
commit cd8aa234fd
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GPG Key ID: EEF712BB5E80EBBA
1 changed files with 4 additions and 3 deletions
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7
llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
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@ -12,6 +12,7 @@
//===----------------------------------------------------------------------===//
#include "ReduceBasicBlocks.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
@ -25,7 +26,7 @@ using namespace llvm;
/// Replaces BB Terminator with one that only contains Chunk BBs
static void replaceBranchTerminator(BasicBlock &BB,
const std::set<BasicBlock *> &BBsToKeep) {
const DenseSet<BasicBlock *> &BBsToKeep) {
auto *Term = BB.getTerminator();
std::vector<BasicBlock *> ChunkSucessors;
for (auto *Succ : successors(&BB))
@ -68,7 +69,7 @@ static void replaceBranchTerminator(BasicBlock &BB,
/// replace with something)
static void
removeUninterestingBBsFromSwitch(SwitchInst &SwInst,
const std::set<BasicBlock *> &BBsToKeep) {
const DenseSet<BasicBlock *> &BBsToKeep) {
if (!BBsToKeep.count(SwInst.getDefaultDest())) {
auto *FnRetTy = SwInst.getParent()->getParent()->getReturnType();
ReturnInst::Create(SwInst.getContext(),
@ -99,7 +100,7 @@ static void extractBasicBlocksFromModule(Oracle &O, Module &Program) {
// We create a vector first, then convert it to a set, so that we don't have
// to pay the cost of rebalancing the set frequently if the order we insert
// the elements doesn't match the order they should appear inside the set.
std::set<BasicBlock *> BBsToKeep(InitBBsToKeep.begin(), InitBBsToKeep.end());
DenseSet<BasicBlock *> BBsToKeep(InitBBsToKeep.begin(), InitBBsToKeep.end());
std::vector<BasicBlock *> BBsToDelete;
for (auto &F : Program)