[PATCH] D64405: [DependenceAnalysis] Dependecies for loads marked with "ivnariant.load" should not be shared with general accesses. Fix for https://bugs.llvm.org/show_bug.cgi?id=42151

[Evgeniy via Phabricator via llvm-commits]

This revision was not accepted when it landed; it landed in state "Needs Review".
This revision was automatically updated to reflect the committed changes.
Closed by commit rG5f026b6d9e88: [DependenceAnalysis] Dependecies for loads marked with "ivnariant.load" should… (authored by ebrevnov).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D64405/new/

https://reviews.llvm.org/D64405

Files:
  llvm/lib/Analysis/MemoryDependenceAnalysis.cpp


Index: llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -979,6 +979,11 @@
     Instruction *QueryInst, const MemoryLocation &Loc, bool isLoad,
     BasicBlock *BB, NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
 
+  bool isInvariantLoad = false;
+
+  if (LoadInst *LI = dyn_cast_or_null<LoadInst>(QueryInst))
+    isInvariantLoad = LI->getMetadata(LLVMContext::MD_invariant_load);
+
   // Do a binary search to see if we already have an entry for this block in
   // the cache set.  If so, find it.
   NonLocalDepInfo::iterator Entry = std::upper_bound(
@@ -990,6 +995,13 @@
   if (Entry != Cache->begin() + NumSortedEntries && Entry->getBB() == BB)
     ExistingResult = &*Entry;
 
+  // Use cached result for invariant load only if there is no dependency for non
+  // invariant load. In this case invariant load can not have any dependency as
+  // well.
+  if (ExistingResult && isInvariantLoad &&
+      !ExistingResult->getResult().isNonFuncLocal())
+    ExistingResult = nullptr;
+
   // If we have a cached entry, and it is non-dirty, use it as the value for
   // this dependency.
   if (ExistingResult && !ExistingResult->getResult().isDirty()) {
@@ -1018,6 +1030,10 @@
   MemDepResult Dep =
       getPointerDependencyFrom(Loc, isLoad, ScanPos, BB, QueryInst);
 
+  // Don't cache results for invariant load.
+  if (isInvariantLoad)
+    return Dep;
+
   // If we had a dirty entry for the block, update it.  Otherwise, just add
   // a new entry.
   if (ExistingResult)
@@ -1454,7 +1470,6 @@
     if (SkipFirstBlock)
       return false;
 
-    bool foundBlock = false;
     for (NonLocalDepEntry &I : llvm::reverse(*Cache)) {
       if (I.getBB() != BB)
         continue;
@@ -1462,14 +1477,12 @@
       assert((GotWorklistLimit || I.getResult().isNonLocal() ||
               !DT.isReachableFromEntry(BB)) &&
              "Should only be here with transparent block");
-      foundBlock = true;
       I.setResult(MemDepResult::getUnknown());
-      Result.push_back(
-          NonLocalDepResult(I.getBB(), I.getResult(), Pointer.getAddr()));
       break;
     }
-    (void)foundBlock; (void)GotWorklistLimit;
-    assert((foundBlock || GotWorklistLimit) && "Current block not in cache?");
+    // Go ahead and report unknown dependence.
+    Result.push_back(
+        NonLocalDepResult(BB, MemDepResult::getUnknown(), Pointer.getAddr()));
   }
 
   // Okay, we're done now.  If we added new values to the cache, re-sort it.


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