[memcpyopt] Teach memcpyopt to optimize across basic blocks
This teaches memcpyopt to make a non-local memdep query when a local query
indicates that the dependency is non-local. This notably allows it to
eliminate many more llvm.memcpy calls in common Rust code, often by 20-30%.
This is r319482 and r319483, along with fixes for PR35519: fix the
optimization that merges stores into memsets to preserve cached memdep
info, and fix memdep's non-local caching strategy to not assume that larger
queries are always more conservative than smaller ones.
Fixes PR28958 and PR35519.
Differential Revision: https://reviews.llvm.org/D40802
llvm-svn: 321138
diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index a6c5901..d5538f5 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -919,6 +919,14 @@
Instruction *QueryInst, SmallVectorImpl<NonLocalDepResult> &Result) {
const MemoryLocation Loc = MemoryLocation::get(QueryInst);
bool isLoad = isa<LoadInst>(QueryInst);
+ return getNonLocalPointerDependencyFrom(QueryInst, Loc, isLoad, Result);
+}
+
+void MemoryDependenceResults::getNonLocalPointerDependencyFrom(
+ Instruction *QueryInst,
+ const MemoryLocation &Loc,
+ bool isLoad,
+ SmallVectorImpl<NonLocalDepResult> &Result) {
BasicBlock *FromBB = QueryInst->getParent();
assert(FromBB);
@@ -1118,21 +1126,15 @@
// If we already have a cache entry for this CacheKey, we may need to do some
// work to reconcile the cache entry and the current query.
if (!Pair.second) {
- if (CacheInfo->Size < Loc.Size) {
- // The query's Size is greater than the cached one. Throw out the
- // cached data and proceed with the query at the greater size.
+ if (CacheInfo->Size != Loc.Size) {
+ // The query's Size differs from the cached one. Throw out the
+ // cached data and proceed with the query at the new size.
CacheInfo->Pair = BBSkipFirstBlockPair();
CacheInfo->Size = Loc.Size;
for (auto &Entry : CacheInfo->NonLocalDeps)
if (Instruction *Inst = Entry.getResult().getInst())
RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
CacheInfo->NonLocalDeps.clear();
- } else if (CacheInfo->Size > Loc.Size) {
- // This query's Size is less than the cached one. Conservatively restart
- // the query using the greater size.
- return getNonLocalPointerDepFromBB(
- QueryInst, Pointer, Loc.getWithNewSize(CacheInfo->Size), isLoad,
- StartBB, Result, Visited, SkipFirstBlock);
}
// If the query's AATags are inconsistent with the cached one,