[MLIR] Enable import of non self referential alias scopes

Author: wsmoses

mlir/include/mlir/Dialect/LLVMIR/LLVMAttrDefs.td

@@ -825,7 +825,7 @@ def LLVM_MemoryEffectsAttr : LLVM_Attr<"MemoryEffects", "memory_effects"> {
 def LLVM_AliasScopeDomainAttr : LLVM_Attr<"AliasScopeDomain",
                                           "alias_scope_domain"> {
   let parameters = (ins
-    "DistinctAttr":$id,
+    "Attribute":$id,
     OptionalParameter<"StringAttr">:$description
   );
 
@@ -853,7 +853,7 @@ def LLVM_AliasScopeDomainAttr : LLVM_Attr<"AliasScopeDomain",
 
 def LLVM_AliasScopeAttr : LLVM_Attr<"AliasScope", "alias_scope"> {
   let parameters = (ins
-    "DistinctAttr":$id,
+    "Attribute":$id,
     "AliasScopeDomainAttr":$domain,
     OptionalParameter<"StringAttr">:$description
   );
@@ -891,6 +891,8 @@ def LLVM_AliasScopeAttr : LLVM_Attr<"AliasScope", "alias_scope"> {
     }
     ```
 
+    The first attribute can either be a DistinctAttribute or a StringAttribute.
+
     See the following link for more details:
     https://llvm.org/docs/LangRef.html#noalias-and-alias-scope-metadata
   }];

mlir/lib/Target/LLVMIR/ModuleImport.cpp

@@ -427,6 +427,11 @@ ModuleImport::processAliasScopeMetadata(const llvm::MDNode *node) {
     return node->getNumOperands() != 0 &&
            node == dyn_cast<llvm::MDNode>(node->getOperand(0));
   };
+  auto verifySelfRefOrString = [](const llvm::MDNode *node) {
+    return node->getNumOperands() != 0 &&
+           (node == dyn_cast<llvm::MDNode>(node->getOperand(0)) ||
+            isa<llvm::MDString>(node->getOperand(0)));
+  };
   // Helper that verifies the given operand is a string or does not exist.
   auto verifyDescription = [](const llvm::MDNode *node, unsigned idx) {
     return idx >= node->getNumOperands() ||
@@ -438,8 +443,14 @@ ModuleImport::processAliasScopeMetadata(const llvm::MDNode *node) {
     if (aliasDomain->getNumOperands() >= 2)
       if (auto *operand = dyn_cast<llvm::MDString>(aliasDomain->getOperand(1)))
         description = builder.getStringAttr(operand->getString());
-    return builder.getAttr<AliasScopeDomainAttr>(
-        DistinctAttr::create(builder.getUnitAttr()), description);
+    Attribute idAttr;
+    if (verifySelfRef(aliasDomain)) {
+      idAttr = DistinctAttr::create(builder.getUnitAttr());
+    } else {
+      auto name = cast<llvm::MDString>(aliasDomain->getOperand(0));
+      idAttr = builder.getStringAttr(name->getString());
+    }
+    return builder.getAttr<AliasScopeDomainAttr>(idAttr, description);
   };
 
   // Collect the alias scopes and domains to translate them.
@@ -452,10 +463,11 @@ ModuleImport::processAliasScopeMetadata(const llvm::MDNode *node) {
       // verifying its domain. Perform the verification before looking it up in
       // the alias scope mapping since it could have been inserted as a domain
       // node before.
-      if (!verifySelfRef(scope) || !domain || !verifyDescription(scope, 2))
+      if (!verifySelfRefOrString(scope) || !domain ||
+          !verifyDescription(scope, 2))
         return emitError(loc) << "unsupported alias scope node: "
                               << diagMD(scope, llvmModule.get());
-      if (!verifySelfRef(domain) || !verifyDescription(domain, 1))
+      if (!verifySelfRefOrString(domain) || !verifyDescription(domain, 1))
         return emitError(loc) << "unsupported alias domain node: "
                               << diagMD(domain, llvmModule.get());
 
@@ -473,9 +485,17 @@ ModuleImport::processAliasScopeMetadata(const llvm::MDNode *node) {
       StringAttr description = nullptr;
       if (!aliasScope.getName().empty())
         description = builder.getStringAttr(aliasScope.getName());
+      Attribute idAttr;
+      if (verifySelfRef(scope)) {
+        idAttr = DistinctAttr::create(builder.getUnitAttr());
+      } else {
+        auto Name = cast<llvm::MDString>(scope->getOperand(0));
+        idAttr = builder.getStringAttr(Name->getString());
+      }
+
       auto aliasScopeOp = builder.getAttr<AliasScopeAttr>(
-          DistinctAttr::create(builder.getUnitAttr()),
-          cast<AliasScopeDomainAttr>(it->second), description);
+          idAttr, cast<AliasScopeDomainAttr>(it->second), description);
+
       aliasScopeMapping.try_emplace(aliasScope.getNode(), aliasScopeOp);
     }
   }

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

@@ -1724,25 +1724,38 @@ ModuleTranslation::getOrCreateAliasScope(AliasScopeAttr aliasScopeAttr) {
       aliasScopeAttr.getDomain(), nullptr);
   if (insertedDomain) {
     llvm::SmallVector<llvm::Metadata *, 2> operands;
-    // Placeholder for self-reference.
+    // Placeholder for potential self-reference.
     operands.push_back(dummy.get());
     if (StringAttr description = aliasScopeAttr.getDomain().getDescription())
       operands.push_back(llvm::MDString::get(ctx, description));
     domainIt->second = llvm::MDNode::get(ctx, operands);
     // Self-reference for uniqueness.
-    domainIt->second->replaceOperandWith(0, domainIt->second);
+    llvm::Metadata *replacement;
+    if (auto stringAttr =
+            dyn_cast<StringAttr>(aliasScopeAttr.getDomain().getId())) {
+      replacement = llvm::MDString::get(ctx, stringAttr.getValue());
+    } else {
+      replacement = domainIt->second;
+    }
+    domainIt->second->replaceOperandWith(0, replacement);
   }
   // Convert the scope metadata node.
   assert(domainIt->second && "Scope's domain should already be valid");
   llvm::SmallVector<llvm::Metadata *, 3> operands;
-  // Placeholder for self-reference.
+  // Placeholder for potential self-reference.
   operands.push_back(dummy.get());
   operands.push_back(domainIt->second);
   if (StringAttr description = aliasScopeAttr.getDescription())
     operands.push_back(llvm::MDString::get(ctx, description));
   scopeIt->second = llvm::MDNode::get(ctx, operands);
   // Self-reference for uniqueness.
-  scopeIt->second->replaceOperandWith(0, scopeIt->second);
+  llvm::Metadata *replacement;
+  if (auto stringAttr = dyn_cast<StringAttr>(aliasScopeAttr.getId())) {
+    replacement = llvm::MDString::get(ctx, stringAttr.getValue());
+  } else {
+    replacement = scopeIt->second;
+  }
+  scopeIt->second->replaceOperandWith(0, replacement);
   return scopeIt->second;
 }
 

mlir/test/Dialect/LLVMIR/roundtrip.mlir

@@ -750,6 +750,16 @@ llvm.func @experimental_noalias_scope_decl() {
   llvm.return
 }
 
+#alias_scope_domain2 = #llvm.alias_scope_domain<id = "domainid", description = "The domain">
+#alias_scope2 = #llvm.alias_scope<id = "stringid", domain = #alias_scope_domain2, description = "The domain">
+
+// CHECK-LABEL: @experimental_noalias_scope_decl
+llvm.func @experimental_noalias_scope_decl2() {
+  // CHECK: llvm.intr.experimental.noalias.scope.decl #{{.*}}
+  llvm.intr.experimental.noalias.scope.decl #alias_scope2
+  llvm.return
+}
+
 // CHECK-LABEL: @experimental_constrained_fptrunc
 llvm.func @experimental_constrained_fptrunc(%in: f64) {
   // CHECK: llvm.intr.experimental.constrained.fptrunc %{{.*}} towardzero ignore : f64 to f32

mlir/test/Target/LLVMIR/Import/metadata-alias-scopes.ll

@@ -92,3 +92,38 @@ declare void @foo(ptr %arg1)
 !0 = distinct !{!0, !"The domain"}
 !1 = !{!1, !0}
 !2 = !{!1}
+
+; // -----
+
+; CHECK: #[[DOMAIN:.*]] = #llvm.alias_scope_domain<id = "domain1">
+; CHECK: #[[$SCOPE0:.*]] = #llvm.alias_scope<id = "scopeid1", domain = #[[DOMAIN]], description = "The first scope">
+; CHECK: #[[$SCOPE1:.*]] = #llvm.alias_scope<id = "scopeid2", domain = #[[DOMAIN]]>
+; CHECK: #[[$SCOPE2:.*]] = #llvm.alias_scope<id = "scopeid3", domain = #[[DOMAIN]]>
+
+; CHECK-LABEL: llvm.func @alias_scope
+define void @alias_scope(ptr %arg1) {
+  ; CHECK: llvm.load
+  ; CHECK-SAME:  alias_scopes = [#[[$SCOPE0]]]
+  ; CHECK-SAME:  noalias_scopes = [#[[$SCOPE1]], #[[$SCOPE2]]]
+  %1 = load i32, ptr %arg1, !alias.scope !4, !noalias !7
+  ; CHECK: llvm.load
+  ; CHECK-SAME:  alias_scopes = [#[[$SCOPE1]]]
+  ; CHECK-SAME:  noalias_scopes = [#[[$SCOPE0]], #[[$SCOPE2]]]
+  %2 = load i32, ptr %arg1, !alias.scope !5, !noalias !8
+  ; CHECK: llvm.load
+  ; CHECK-SAME:  alias_scopes = [#[[$SCOPE2]]]
+  ; CHECK-SAME:  noalias_scopes = [#[[$SCOPE0]], #[[$SCOPE1]]]
+  %3 = load i32, ptr %arg1, !alias.scope !6, !noalias !9
+  ret void
+}
+
+!0 = !{!"domain1"}
+!1 = !{!"scopeid1", !0, !"The first scope"}
+!2 = !{!"scopeid2", !0}
+!3 = !{!"scopeid3", !0}
+!4 = !{!1}
+!5 = !{!2}
+!6 = !{!3}
+!7 = !{!2, !3}
+!8 = !{!1, !3}
+!9 = !{!1, !2}

mlir/test/Target/LLVMIR/attribute-alias-scopes.mlir

@@ -104,3 +104,54 @@ llvm.func @self_reference() {
 // CHECK-DAG: ![[SCOPES]] = !{![[SCOPE]]}
 // CHECK-DAG: = !DISubroutineType(types: ![[TYPES:[0-9]+]])
 // CHECK-DAG: ![[TYPES]] = !{null}
+
+// -----
+
+llvm.func @foo(%arg0: !llvm.ptr)
+
+#alias_scope_domain = #llvm.alias_scope_domain<id = "domain1", description = "The domain">
+#alias_scope1 = #llvm.alias_scope<id = "scope1", domain = #alias_scope_domain, description = "The first scope">
+#alias_scope2 = #llvm.alias_scope<id = "scope2", domain = #alias_scope_domain>
+#alias_scope3 = #llvm.alias_scope<id = "scope3", domain = #alias_scope_domain>
+
+// CHECK-LABEL: @alias_scopes
+llvm.func @alias_scopes(%arg1 : !llvm.ptr) {
+  %0 = llvm.mlir.constant(0 : i32) : i32
+  // CHECK:  call void @llvm.experimental.noalias.scope.decl(metadata ![[SCOPES1:[0-9]+]])
+  llvm.intr.experimental.noalias.scope.decl #alias_scope1
+  // CHECK:  store {{.*}}, !alias.scope ![[SCOPES1]], !noalias ![[SCOPES23:[0-9]+]]
+  llvm.store %0, %arg1 {alias_scopes = [#alias_scope1], noalias_scopes = [#alias_scope2, #alias_scope3]} : i32, !llvm.ptr
+  // CHECK:  load {{.*}}, !alias.scope ![[SCOPES2:[0-9]+]], !noalias ![[SCOPES13:[0-9]+]]
+  %1 = llvm.load %arg1 {alias_scopes = [#alias_scope2], noalias_scopes = [#alias_scope1, #alias_scope3]} : !llvm.ptr -> i32
+  // CHECK:  atomicrmw {{.*}}, !alias.scope ![[SCOPES3:[0-9]+]], !noalias ![[SCOPES12:[0-9]+]]
+  %2 = llvm.atomicrmw add %arg1, %0 monotonic {alias_scopes = [#alias_scope3], noalias_scopes = [#alias_scope1, #alias_scope2]} : !llvm.ptr, i32
+  // CHECK:  cmpxchg {{.*}}, !alias.scope ![[SCOPES3]]
+  %3 = llvm.cmpxchg %arg1, %1, %2 acq_rel monotonic {alias_scopes = [#alias_scope3]} : !llvm.ptr, i32
+  %5 = llvm.mlir.constant(42 : i8) : i8
+  // CHECK:  llvm.memcpy{{.*}}, !alias.scope ![[SCOPES3]]
+  "llvm.intr.memcpy"(%arg1, %arg1, %0) <{isVolatile = false}> {alias_scopes = [#alias_scope3]} : (!llvm.ptr, !llvm.ptr, i32) -> ()
+  // CHECK:  llvm.memset{{.*}}, !noalias ![[SCOPES3]]
+  "llvm.intr.memset"(%arg1, %5, %0) <{isVolatile = false}> {noalias_scopes = [#alias_scope3]} : (!llvm.ptr, i8, i32) -> ()
+  // CHECK: call void @foo({{.*}} !alias.scope ![[SCOPES3]]
+  llvm.call @foo(%arg1) {alias_scopes = [#alias_scope3]} : (!llvm.ptr) -> ()
+  // CHECK: call void @foo({{.*}} !noalias ![[SCOPES3]]
+  llvm.call @foo(%arg1) {noalias_scopes = [#alias_scope3]} : (!llvm.ptr) -> ()
+  llvm.return
+}
+
+// Check the intrinsic declarations.
+// CHECK-DAG: declare void @llvm.experimental.noalias.scope.decl(metadata)
+// CHECK-DAG: declare void @llvm.memcpy.p0.p0.i32(ptr noalias nocapture writeonly, ptr noalias nocapture readonly, i32, i1 immarg)
+// CHECK-DAG: declare void @llvm.memset.p0.i32(ptr nocapture writeonly, i8, i32, i1 immarg)
+
+// Check the translated metadata.
+// CHECK-DAG: ![[DOMAIN:[0-9]+]] = !{!"domain1", !"The domain"}
+// CHECK-DAG: ![[SCOPE1:[0-9]+]] = !{!"scope1", ![[DOMAIN]], !"The first scope"}
+// CHECK-DAG: ![[SCOPE2:[0-9]+]] = !{!"scope2", ![[DOMAIN]]}
+// CHECK-DAG: ![[SCOPE3:[0-9]+]] = !{!"scope3", ![[DOMAIN]]}
+// CHECK-DAG: ![[SCOPES1]] = !{![[SCOPE1]]}
+// CHECK-DAG: ![[SCOPES2]] = !{![[SCOPE2]]}
+// CHECK-DAG: ![[SCOPES3]] = !{![[SCOPE3]]}
+// CHECK-DAG: ![[SCOPES12]] = !{![[SCOPE1]], ![[SCOPE2]]}
+// CHECK-DAG: ![[SCOPES13]] = !{![[SCOPE1]], ![[SCOPE3]]}
+// CHECK-DAG: ![[SCOPES23]] = !{![[SCOPE2]], ![[SCOPE3]]}