Enhance GVN to do more precise alias queries for non-local memory
references. For example, this allows gvn to eliminate the load in
this example:
void foo(int n, int* p, int *q) {
p[0] = 0;
p[1] = 1;
if (n) {
*q = p[0];
}
}
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118714 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index c72cd1e..b4c6d09 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -741,16 +741,40 @@
// Look up the cached info for Pointer.
ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad);
- NonLocalPointerInfo *CacheInfo = &NonLocalPointerDeps[CacheKey];
- // If this query's TBAATag is inconsistent with the cached one, discard the
- // tag and restart the query.
- if (CacheInfo->TBAATag != Loc.TBAATag) {
- CacheInfo->TBAATag = 0;
- NonLocalPointerDeps.erase(CacheKey);
- return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(),
- isLoad, StartBB, Result, Visited,
- SkipFirstBlock);
+ // Set up a temporary NLPI value. If the map doesn't yet have an entry for
+ // CacheKey, this value will be inserted as the associated value. Otherwise,
+ // it'll be ignored, and we'll have to check to see if the cached size and
+ // tbaa tag are consistent with the current query.
+ NonLocalPointerInfo InitialNLPI;
+ InitialNLPI.Size = Loc.Size;
+ InitialNLPI.TBAATag = Loc.TBAATag;
+
+ // Get the NLPI for CacheKey, inserting one into the map if it doesn't
+ // already have one.
+ std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair =
+ NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI));
+ NonLocalPointerInfo *CacheInfo = &Pair.first->second;
+
+ if (!Pair.second) {
+ // If this query's Size is inconsistent with the cached one, take the
+ // maximum size and restart the query.
+ if (CacheInfo->Size != Loc.Size) {
+ CacheInfo->Size = std::max(CacheInfo->Size, Loc.Size);
+ return getNonLocalPointerDepFromBB(Pointer,
+ Loc.getWithNewSize(CacheInfo->Size),
+ isLoad, StartBB, Result, Visited,
+ SkipFirstBlock);
+ }
+
+ // If this query's TBAATag is inconsistent with the cached one, discard the
+ // tag and restart the query.
+ if (CacheInfo->TBAATag != Loc.TBAATag) {
+ CacheInfo->TBAATag = 0;
+ return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(),
+ isLoad, StartBB, Result, Visited,
+ SkipFirstBlock);
+ }
}
NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps;
@@ -796,6 +820,7 @@
CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
else {
CacheInfo->Pair = BBSkipFirstBlockPair();
+ CacheInfo->Size = 0;
CacheInfo->TBAATag = 0;
}
@@ -921,6 +946,7 @@
// cached value to do more work but not miss the phi trans failure.
NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey];
NLPI.Pair = BBSkipFirstBlockPair();
+ NLPI.Size = 0;
NLPI.TBAATag = 0;
continue;
}
@@ -949,6 +975,7 @@
// specific block queries) but we can't do the fastpath "return all
// results from the set" Clear out the indicator for this.
CacheInfo->Pair = BBSkipFirstBlockPair();
+ CacheInfo->Size = 0;
CacheInfo->TBAATag = 0;
SkipFirstBlock = false;
continue;
@@ -967,6 +994,7 @@
// specific block queries) but we can't do the fastpath "return all
// results from the set". Clear out the indicator for this.
CacheInfo->Pair = BBSkipFirstBlockPair();
+ CacheInfo->Size = 0;
CacheInfo->TBAATag = 0;
// If *nothing* works, mark the pointer as being clobbered by the first
@@ -1184,6 +1212,7 @@
// The cache is not valid for any specific block anymore.
NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair();
+ NonLocalPointerDeps[P].Size = 0;
NonLocalPointerDeps[P].TBAATag = 0;
// Update any entries for RemInst to use the instruction after it.