Pass QueryInst down through non-local dependency calculation

This change is mostly motivated by exposing information about the original query instruction to the actual scanning work in getPointerDependencyFrom when used by GVN PRE. In a follow up change, I will use this to be more precise with regards to the semantics of volatile instructions encountered in the scan of a basic block.

Worth noting, is that this change (despite appearing quite simple) is not semantically preserving. By providing more information to the helper routine, we allow some optimizations to kick in that weren't previously able to (when called from this code path.) In particular, we see that treatment of !invariant.load becomes more precise. In theory, we might see a difference with an ordered/atomic instruction as well, but I'm having a hard time actually finding a test case which shows that.

Test wise, I've included new tests for !invariant.load which illustrate this difference. I've also included some updated TBAA tests which highlight that this change isn't needed for that optimization to kick in - it's handled inside alias analysis itself. 

Eventually, it would be nice to factor the !invariant.load handling inside alias analysis as well.

Differential Revision: http://reviews.llvm.org/D6895

llvm-svn: 227110

1 files changed, 13 insertions, 8 deletions

diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index c505aa48817..0f3307c21b1 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -924,7 +924,7 @@ getNonLocalPointerDependency(Instruction *QueryInst,
   // a block with multiple different pointers.  This can happen during PHI
   // translation.
   DenseMap<BasicBlock*, Value*> Visited;
-  if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB,
+  if (!getNonLocalPointerDepFromBB(QueryInst, Address, Loc, isLoad, FromBB,
                                    Result, Visited, true))
     return;
   Result.clear();
@@ -938,7 +938,8 @@ getNonLocalPointerDependency(Instruction *QueryInst,
 /// lookup (which may use dirty cache info if available).  If we do a lookup,
 /// add the result to the cache.
 MemDepResult MemoryDependenceAnalysis::
-GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
+GetNonLocalInfoForBlock(Instruction *QueryInst,
+                        const AliasAnalysis::Location &Loc,
                         bool isLoad, BasicBlock *BB,
                         NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
 
@@ -979,7 +980,8 @@ GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
   }
 
   // Scan the block for the dependency.
-  MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB);
+  MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB,
+                                              QueryInst);
 
   // If we had a dirty entry for the block, update it.  Otherwise, just add
   // a new entry.
@@ -1052,7 +1054,8 @@ SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
 /// not compute dependence information for some reason.  This should be treated
 /// as a clobber dependence on the first instruction in the predecessor block.
 bool MemoryDependenceAnalysis::
-getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
+getNonLocalPointerDepFromBB(Instruction *QueryInst,
+                            const PHITransAddr &Pointer,
                             const AliasAnalysis::Location &Loc,
                             bool isLoad, BasicBlock *StartBB,
                             SmallVectorImpl<NonLocalDepResult> &Result,
@@ -1091,7 +1094,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
     } 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(Pointer,
+      return getNonLocalPointerDepFromBB(QueryInst, Pointer,
                                          Loc.getWithNewSize(CacheInfo->Size),
                                          isLoad, StartBB, Result, Visited,
                                          SkipFirstBlock);
@@ -1111,7 +1114,8 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
         CacheInfo->NonLocalDeps.clear();
       }
       if (Loc.AATags)
-        return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutAATags(),
+        return getNonLocalPointerDepFromBB(QueryInst,
+                                           Pointer, Loc.getWithoutAATags(),
                                            isLoad, StartBB, Result, Visited,
                                            SkipFirstBlock);
     }
@@ -1214,7 +1218,8 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
       // Get the dependency info for Pointer in BB.  If we have cached
       // information, we will use it, otherwise we compute it.
       DEBUG(AssertSorted(*Cache, NumSortedEntries));
-      MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache,
+      MemDepResult Dep = GetNonLocalInfoForBlock(QueryInst,
+                                                 Loc, isLoad, BB, Cache,
                                                  NumSortedEntries);
 
       // If we got a Def or Clobber, add this to the list of results.
@@ -1348,7 +1353,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
       // result conflicted with the Visited list; we have to conservatively
       // assume it is unknown, but this also does not block PRE of the load.
       if (!CanTranslate ||
-          getNonLocalPointerDepFromBB(PredPointer,
+          getNonLocalPointerDepFromBB(QueryInst, PredPointer,
                                       Loc.getWithNewPtr(PredPtrVal),
                                       isLoad, Pred,
                                       Result, Visited)) {