[MemDep] Also remove load instructions from NonLocalDesCache.

[fhahn]

Summary

Currently load instructions are added to the cache for invariant pointer
group dependencies, but only pointer values are removed currently. That
leads to dangling AssertingVHs in the test case below, where we delete a
load from an invariant pointer group. We should also remove the entries
from the cache.

Fixes PR46054.

[efriedma]

llvm/lib/Analysis/MemoryDependenceAnalysis.cpp

1531

The comment says "otherwise"; should this be an else-if?

[fhahn]

Reword comments.

[fhahn]

llvm/lib/Analysis/MemoryDependenceAnalysis.cpp

1531

Yes the otherwise refers to the preceding if. I move it into the else branch and also added a version of the test case that loads a pointer value.

[efriedma]

LGTM

[fhahn]

Move code to else and add test case that loads a pointer.

[fhahn]

Just realized that the latest version got stuck while uploading. The latest version with the extra test case and the code in the else is now available.

[efriedma]

Oh, that makes more sense. Still LGTM

llvm/lib/Analysis/MemoryDependenceAnalysis.cpp

if (LocalDepEntry != LocalDeps.end()) {
     // Remove us from DepInst's reverse set now that the local dep info is gone.
     if (Instruction *Inst = LocalDepEntry->second.getInst())
       RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst);
 
     // Remove this local dependency info.
     LocalDeps.erase(LocalDepEntry);
   }
 
-  // If we have any cached pointer dependencies on this instruction, remove
-  // them.  If the instruction has non-pointer type, then it can't be a pointer
-  // base.
+  // If we have any cached dependencies on this instruction, remove
+  // them.
 
-  // Remove it from both the load info and the store info.  The instruction
-  // can't be in either of these maps if it is non-pointer.
+  // If the instruction is a pointer, Remove it from both the load info and the
+  // store info.
   if (RemInst->getType()->isPointerTy()) {
     RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false));
     RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true));
   }
 
+  // If the instructions is in the map directly, it must be a load. Remove it.
+  auto toRemoveIt = NonLocalDefsCache.find(RemInst);
+  if (toRemoveIt != NonLocalDefsCache.end()) {
+    assert(isa<LoadInst>(RemInst) &&
+           "only load instructions should be added directly");
+    const Instruction *DepV = toRemoveIt->second.getResult().getInst();
+    ReverseNonLocalDefsCache.find(DepV)->second.erase(RemInst);
+    NonLocalDefsCache.erase(toRemoveIt);
+  }
+
   // Loop over all of the things that depend on the instruction we're removing.
   SmallVector<std::pair<Instruction *, Instruction *>, 8> ReverseDepsToAdd;
 
   // If we find RemInst as a clobber or Def in any of the maps for other values,
   // we need to replace its entry with a dirty version of the instruction after
   // it.  If RemInst is a terminator, we use a null dirty value.
   //
   // Using a dirty version of the instruction after RemInst saves having to scan

llvm/test/Transforms/GVN/pr46054-md-nonlocaldefcache-cleanup.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -gvn -S %s | FileCheck %s
+
+; Test for PR46054. Make sure we correctly invalidate MemoryDependenceAnalysis,
+; after removing a nonlocaldef.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @test(double* %data) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[LUC:%.*]] = tail call noalias nonnull i64* @data()
+; CHECK-NEXT:    store i64 1, i64* [[LUC]], align 8, !invariant.group !0
+; CHECK-NEXT:    call void @fn(i64 1)
+; CHECK-NEXT:    br i1 true, label [[A:%.*]], label [[ENTRY_B_CRIT_EDGE:%.*]]
+; CHECK:       entry.B_crit_edge:
+; CHECK-NEXT:    br label [[B:%.*]]
+; CHECK:       A:
+; CHECK-NEXT:    br label [[B]]
+; CHECK:       B:
+; CHECK-NEXT:    call void @fn(i64 1)
+; CHECK-NEXT:    ret void
+;
+entry:
+  %luc = tail call noalias nonnull i64* @data()
+  store i64 1, i64* %luc, !invariant.group !0
+  %QQ = load i64, i64* %luc, !invariant.group !0
+  call void @fn(i64 %QQ)
+  br i1 true, label %A, label %B
+
+A:                                                ; preds = %loop
+  br label %B
+
+B:                                                ; preds = %A, %loop
+  %QQ.1 = load i64, i64* %luc, !invariant.group !0
+  call void @fn(i64 %QQ.1)
+  ret void
+}
+
+declare void @fn(i64)
+
+declare noalias i64* @data()
+
+!0 = distinct !{}