[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%.

Fixes PR28958.

Differential Revision: https://reviews.llvm.org/D38374

llvm-svn: 319482

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index ba90f1cf2fb..d41b6be75f2 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -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);