[GlobalDCE] Use DenseMap instead of unordered_multimap for GVDependencies.
Summary:
std::unordered_multimap happens to be very slow when the number of elements
grows large. On one of our internal applications we observed a 17x compile time
improvement from changing it to DenseMap.
Reviewers: mehdi_amini, serge-sans-paille, davide
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38916
llvm-svn: 316045
diff --git a/llvm/lib/Transforms/IPO/GlobalDCE.cpp b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
index c91e8b4..1f354e8 100644
--- a/llvm/lib/Transforms/IPO/GlobalDCE.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
@@ -115,7 +115,7 @@
ComputeDependencies(User, Deps);
Deps.erase(&GV); // Remove self-reference.
for (GlobalValue *GVU : Deps) {
- GVDependencies.insert(std::make_pair(GVU, &GV));
+ GVDependencies[GVU].insert(&GV);
}
}
@@ -199,8 +199,8 @@
AliveGlobals.end()};
while (!NewLiveGVs.empty()) {
GlobalValue *LGV = NewLiveGVs.pop_back_val();
- for (auto &&GVD : make_range(GVDependencies.equal_range(LGV)))
- MarkLive(*GVD.second, &NewLiveGVs);
+ for (auto *GVD : GVDependencies[LGV])
+ MarkLive(*GVD, &NewLiveGVs);
}
// Now that all globals which are needed are in the AliveGlobals set, we loop