[MemorySSA] Don't create new memory accesses for dbg intrinsics in MemorySSA

[ChuanqiXu]

Summary

After we landed https://reviews.llvm.org/D127383, the compiler may crash at: https://github.com/llvm/llvm-project/blob/051738b08cf5e39fd274dd379147d1c19e2b5b20/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp#L687-L691.

This is because the dbg intrinsics are readnone originally and the MemorySSA would refuse to create a new memory access at https://github.com/llvm/llvm-project/blob/051738b08cf5e39fd274dd379147d1c19e2b5b20/llvm/lib/Analysis/MemorySSA.cpp#L1830-L1831

But after D127383, it wouldn't be true for the dbg intrinsics in presplit coroutine. So here is the crash.

[ChuanqiXu]

Add unit tests.

[ChuanqiXu]

llvm/lib/Analysis/MemorySSA.cpp

1780–1782

Given these comments, the following changes look reasonable.

[asbirlea]

LGTM.

[ChuanqiXu]

We prefer https://reviews.llvm.org/D135550

llvm/lib/Analysis/MemorySSA.cpp

 }
 
 /// Helper function to create new memory accesses
 template <typename AliasAnalysisType>
 MemoryUseOrDef *MemorySSA::createNewAccess(Instruction *I,
                                            AliasAnalysisType *AAP,
                                            const MemoryUseOrDef *Template) {
   // The assume intrinsic has a control dependency which we model by claiming
   // that it writes arbitrarily. Debuginfo intrinsics may be considered
   // clobbers when we have a nonstandard AA pipeline. Ignore these fake memory
   // dependencies here.
   // FIXME: Replace this special casing with a more accurate modelling of
   // assume's control dependency.
   if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
     switch (II->getIntrinsicID()) {
     default:
       break;
     case Intrinsic::assume:
     case Intrinsic::experimental_noalias_scope_decl:
     case Intrinsic::pseudoprobe:
+    case Intrinsic::dbg_addr:
+    case Intrinsic::dbg_declare:
+    case Intrinsic::dbg_label:
+    case Intrinsic::dbg_value:
       return nullptr;
     }
   }
 
   // Using a nonstandard AA pipelines might leave us with unexpected modref
   // results for I, so add a check to not model instructions that may not read
   // from or write to memory. This is necessary for correctness.
   if (!I->mayReadFromMemory() && !I->mayWriteToMemory())

llvm/unittests/Analysis/MemorySSATest.cpp

// traverse incorrectly.
     Instruction *LI = getInstructionByName(*F, "v2");
     LI->moveBefore(BB->getTerminator());
     // Check that there is no assertion of "Incomplete phi during partial
     // rename"
     if (MemoryUseOrDef *MUD = MSSA.getMemoryAccess(LI))
       Updater.moveToPlace(MUD, BB, MemorySSA::BeforeTerminator);
   }
 }
+
+TEST_F(MemorySSATest, TestNoDbgInsts) {
+  SMDiagnostic E;
+  auto M = parseAssemblyString(R"(
+      define void @test() presplitcoroutine {
+      entry:
+        %i = alloca i32
+        call void @llvm.dbg.declare(metadata ptr %i, metadata !6, metadata !DIExpression()), !dbg !10
+        call void @llvm.dbg.value(metadata ptr %i, metadata !6, metadata !DIExpression()), !dbg !10
+        ret void
+      }
+
+      declare void @llvm.dbg.declare(metadata, metadata, metadata) nocallback nofree nosync nounwind readnone speculatable willreturn
+      declare void @llvm.dbg.value(metadata, metadata, metadata) nocallback nofree nosync nounwind readnone speculatable willreturn
+
+      !llvm.dbg.cu = !{!0}
+
+      !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 15.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !2, splitDebugInlining: false, nameTableKind: None)
+      !1 = !DIFile(filename: "repro.cpp", directory: ".")
+      !2 = !{}
+      !3 = !{i32 7, !"Dwarf Version", i32 4}
+      !4 = !{i32 2, !"Debug Info Version", i32 3}
+      !5 = !{!"clang version 15.0.0"}
+      !6 = !DILocalVariable(name: "i", scope: !7, file: !1, line: 24, type: !10)
+      !7 = distinct !DILexicalBlock(scope: !8, file: !1, line: 23, column: 12)
+      !8 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope: !1, file: !1, line: 23, type: !9, scopeLine: 23, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+      !9 = !DISubroutineType(types: !2)
+      !10 = !DILocation(line: 24, column: 7, scope: !7)
+    )",
+    E, C);
+  ASSERT_TRUE(M);
+  F = M->getFunction("test");
+  ASSERT_TRUE(F);
+  setupAnalyses();
+  MemorySSA &MSSA = *Analyses->MSSA;
+  MemorySSAUpdater Updater(&MSSA);
+
+  BasicBlock &Entry = F->front();
+  auto I = Entry.begin();
+  Instruction *DbgDeclare = cast<Instruction>(I++);
+  Instruction *DbgValue = cast<Instruction>(I++);
+  ASSERT_EQ(MSSA.getMemoryAccess(DbgDeclare), nullptr);
+  ASSERT_EQ(MSSA.getMemoryAccess(DbgValue), nullptr);
+}
+