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[memcpyopt] Teach memcpyopt to optimize across basic blocks

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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


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321138 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2017-12-20 01:36:25 +00:00
parent 81228ec561
commit 06400502e2
7 changed files with 306 additions and 19 deletions
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lib/Analysis/MemoryDependenceAnalysis.cpp
+11 -9
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@@ -919,6 +919,14 @@ void MemoryDependenceResults::getNonLocalPointerDependency(
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 @@ bool MemoryDependenceResults::getNonLocalPointerDepFromBB(
// 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,