[LiveDebugValues] Cache LexicalScopes::getMachineBasicBlocks, NFCI
Summary:
Cache the results from getMachineBasicBlocks in LexicalScopes to speed
up UserValueScopes::dominates queries. This replaces the caching done
in UserValueScopes. Compared to the old caching method, this reduces
memory traffic when a VarLoc is copied (e.g. when a VarLocMap grows),
and enables caching across basic blocks.
When compiling sqlite 3.5.7 (CTMark version), this patch reduces the
number of calls to getMachineBasicBlocks from 10,207 to 1,093. I also
measured a small compile-time reduction (~ 0.1% of total wall time, on
average, on my machine).
As a drive-by, I made the DebugLoc in UserValueScopes a const reference
to cut down on MetadataTracking traffic.
Reviewers: jmorse, Orlando, aprantl, nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D80957
diff --git a/llvm/lib/CodeGen/LexicalScopes.cpp b/llvm/lib/CodeGen/LexicalScopes.cpp
index be1d4c8..c5d786b 100644
--- a/llvm/lib/CodeGen/LexicalScopes.cpp
+++ b/llvm/lib/CodeGen/LexicalScopes.cpp
@@ -44,6 +44,7 @@
AbstractScopeMap.clear();
InlinedLexicalScopeMap.clear();
AbstractScopesList.clear();
+ DominatedBlocks.clear();
}
/// initialize - Scan machine function and constuct lexical scope nest.
@@ -302,8 +303,6 @@
MBBs.insert(&*CurMBBIt);
}
-/// dominates - Return true if DebugLoc's lexical scope dominates at least one
-/// machine instruction's lexical scope in a given machine basic block.
bool LexicalScopes::dominates(const DILocation *DL, MachineBasicBlock *MBB) {
assert(MF && "Unexpected uninitialized LexicalScopes object!");
LexicalScope *Scope = getOrCreateLexicalScope(DL);
@@ -315,11 +314,17 @@
return true;
// Fetch all the blocks in DLs scope. Because the range / block list also
- // contain any subscopes, any instruction that DL dominates can be found
- // in the block set.
- SmallPtrSet<const MachineBasicBlock *, 32> Set;
- getMachineBasicBlocks(DL, Set);
- return Set.count(MBB) != 0;
+ // contain any subscopes, any instruction that DL dominates can be found in
+ // the block set.
+ //
+ // Cache the set of fetched blocks to avoid repeatedly recomputing the set in
+ // the LiveDebugValues pass.
+ std::unique_ptr<BlockSetT> &Set = DominatedBlocks[DL];
+ if (!Set) {
+ Set = std::make_unique<BlockSetT>();
+ getMachineBasicBlocks(DL, *Set);
+ }
+ return Set->count(MBB) != 0;
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)