[MemoryDependence] Fix invariant group store

[wsmoses]

Summary

Fix bug in MemoryDependence [and thus GVN] for invariant group

[jdoerfert]

The test needs to be simplified, remove malloc and print, all geps and bitcasts, metadata, flags, ... everything except the store %p, %p_ptr and the load %p.

Explain in the commit message what the patch does, sure it fixes an error, but what error, e.g., a store is only invariant to a load if the pointer operands are the same.

Other than that, the logic is sound and fixes the problem.

[wsmoses]

Minimize test

[jdoerfert]

LG, with the updated commit message.

llvm/lib/Analysis/MemoryDependenceAnalysis.cpp

for (const Use &Us : Ptr->uses()) {
         if (GEP->hasAllZeroIndices()) {
           LoadOperandsQueue.push_back(U);
           continue;
         }
 
       // If we hit load/store with the same invariant.group metadata (and the
       // same pointer operand) we can assume that value pointed by pointer
       // operand didn't change.
-      if ((isa<LoadInst>(U) || isa<StoreInst>(U)) &&
+      if ((isa<LoadInst>(U) ||
+           (isa<StoreInst>(U) &&
+            cast<StoreInst>(U)->getPointerOperand() == Ptr)) &&
           U->hasMetadata(LLVMContext::MD_invariant_group))
         ClosestDependency = GetClosestDependency(ClosestDependency, U);
     }
   }
 
   if (!ClosestDependency)
     return MemDepResult::getUnknown();
   if (ClosestDependency->getParent() == BB)

llvm/test/Transforms/GVN/storeinvgroup.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -gvn -S -o - < %s | FileCheck %s
+
+define double @code(double* %a1) {
+; CHECK-LABEL: @code(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[META:%.*]] = alloca double*, align 8
+; CHECK-NEXT:    store double 1.234500e+00, double* [[A1:%.*]], align 8
+; CHECK-NEXT:    store double* [[A1]], double** [[META]], align 8, !invariant.group !0
+; CHECK-NEXT:    ret double 1.234500e+00
+;
+entry:
+  %meta = alloca double*
+  store double 1.23450000e+00, double* %a1, align 8
+  store double* %a1, double** %meta, align 8, !invariant.group !0
+  %iload = load double, double* %a1, align 8, !invariant.group !1
+  ret double %iload
+}
+
+!0 = distinct !{}
+!1 = distinct !{}