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[mlir][llvm] Fix access group translation #83257

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Merged
merged 1 commit into from
Feb 28, 2024
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[mlir][llvm] Fix access group translation #83257

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5 changes: 3 additions & 2 deletions mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1512,13 +1512,14 @@ ModuleTranslation::getOrCreateAliasScope(AliasScopeAttr aliasScopeAttr) {
if (!scopeInserted)
return scopeIt->second;
llvm::LLVMContext &ctx = llvmModule->getContext();
auto dummy = llvm::MDNode::getTemporary(ctx, std::nullopt);
// Convert the domain metadata node if necessary.
auto [domainIt, insertedDomain] = aliasDomainMetadataMapping.try_emplace(
aliasScopeAttr.getDomain(), nullptr);
if (insertedDomain) {
llvm::SmallVector<llvm::Metadata *, 2> operands;
// Placeholder for self-reference.
operands.push_back({});
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);
Expand All @@ -1529,7 +1530,7 @@ ModuleTranslation::getOrCreateAliasScope(AliasScopeAttr aliasScopeAttr) {
assert(domainIt->second && "Scope's domain should already be valid");
llvm::SmallVector<llvm::Metadata *, 3> operands;
// Placeholder for self-reference.
operands.push_back({});
operands.push_back(dummy.get());
operands.push_back(domainIt->second);
if (StringAttr description = aliasScopeAttr.getDescription())
operands.push_back(llvm::MDString::get(ctx, description));
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44 changes: 39 additions & 5 deletions mlir/test/Target/LLVMIR/attribute-alias-scopes.mlir
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Expand Up @@ -59,14 +59,48 @@ llvm.func @alias_scopes(%arg1 : !llvm.ptr) {
#alias_scope1 = #llvm.alias_scope<id = distinct[1]<>, domain = #alias_scope_domain>

// CHECK-LABEL: @noalias_intr_only
llvm.func @noalias_intr_only(%arg1 : !llvm.ptr) {
%0 = llvm.mlir.constant(0 : i32) : i32
// CHECK: call void @llvm.experimental.noalias.scope.decl(metadata ![[SCOPES1:[0-9]+]])
llvm.func @noalias_intr_only() {
// CHECK: call void @llvm.experimental.noalias.scope.decl(metadata ![[SCOPES:[0-9]+]])
llvm.intr.experimental.noalias.scope.decl #alias_scope1
llvm.return
}

// Check the translated metadata.
// CHECK-DAG: ![[DOMAIN:[0-9]+]] = distinct !{![[DOMAIN]], !"The domain"}
// CHECK-DAG: ![[SCOPE1:[0-9]+]] = distinct !{![[SCOPE1]], ![[DOMAIN]]}
// CHECK-DAG: ![[SCOPES1]] = !{![[SCOPE1]]}
// CHECK-DAG: ![[SCOPE:[0-9]+]] = distinct !{![[SCOPE]], ![[DOMAIN]]}
// CHECK-DAG: ![[SCOPES]] = !{![[SCOPE]]}

// -----

// This test ensures the alias scope translation creates a temporary metadata
// node as a placeholder for self-references. Without this, the debug info
// translation of a type list with a null entry could inadvertently reference
// access group metadata. This occurs when both translations generate a metadata
// list with a null entry, which are then uniqued to the same metadata node.
// The access group translation subsequently updates the null entry to a
// self-reference, which causes the type list to reference the access
// group node as well. The use of a temporary placeholder node avoids the issue.

#alias_scope_domain = #llvm.alias_scope_domain<id = distinct[0]<>>
#alias_scope = #llvm.alias_scope<id = distinct[1]<>, domain = #alias_scope_domain>

#di_null_type = #llvm.di_null_type
#di_subroutine_type = #llvm.di_subroutine_type<types = #di_null_type>
#di_file = #llvm.di_file<"attribute-alias-scope.mlir" in "">
#di_compile_unit = #llvm.di_compile_unit<id = distinct[3]<>, sourceLanguage = DW_LANG_C11, file = #di_file, isOptimized = true, emissionKind = Full>
#di_subprogram = #llvm.di_subprogram<id = distinct[2]<>, compileUnit = #di_compile_unit, scope = #di_file, file = #di_file, subprogramFlags = "Definition", type = #di_subroutine_type>

// CHECK-LABEL: @self_reference
llvm.func @self_reference() {
// CHECK: call void @llvm.experimental.noalias.scope.decl(metadata ![[SCOPES:[0-9]+]])
llvm.intr.experimental.noalias.scope.decl #alias_scope
llvm.return
} loc(fused<#di_subprogram>[unknown])

// Check that the translated subroutine types do not reference the access group
// domain since both of them are created as metadata list with a null entry.
// CHECK-DAG: ![[DOMAIN:[0-9]+]] = distinct !{![[DOMAIN]]}
// CHECK-DAG: ![[SCOPE:[0-9]+]] = distinct !{![[SCOPE]], ![[DOMAIN]]}
// CHECK-DAG: ![[SCOPES]] = !{![[SCOPE]]}
// CHECK-DAG: = !DISubroutineType(types: ![[TYPES:[0-9]+]])
// CHECK-DAG: ![[TYPES]] = !{null}