[mlir] Support llvm.readonly attribute on llvm pointers

[guraypp]

Summary

The attribute is translated into LLVM's function attribute 'readonly'. The attribute can be only used for pointers.

[guraypp]

add invalid test

mlir/include/mlir/Dialect/LLVMIR/LLVMOpBase.td

def LLVM_Dialect : Dialect {
   let hasRegionResultAttrVerify = 1;
   let hasOperationAttrVerify = 1;
 
   let extraClassDeclaration = [{
     /// Name of the data layout attributes.
     static StringRef getDataLayoutAttrName() { return "llvm.data_layout"; }
     static StringRef getAlignAttrName() { return "llvm.align"; }
     static StringRef getNoAliasAttrName() { return "llvm.noalias"; }
+    static StringRef getReadonlyAttrName() { return "llvm.readonly"; }
     static StringRef getNoAliasScopesAttrName() { return "noalias_scopes"; }
     static StringRef getAliasScopesAttrName() { return "alias_scopes"; }
     static StringRef getLoopAttrName() { return "llvm.loop"; }
     static StringRef getParallelAccessAttrName() { return "parallel_access"; }
     static StringRef getLoopOptionsAttrName() { return "options"; }
     static StringRef getAccessGroupsAttrName() { return "access_groups"; }
     static StringRef getStructAttrsAttrName() { return "llvm.struct_attrs"; }
     static StringRef getByValAttrName() { return "llvm.byval"; }

mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp

if (name == LLVMDialect::getNoAliasAttrName()) {
       if (!attrValue.isa<UnitAttr>())
         return op->emitError() << "expected llvm.noalias result attribute to "
                                   "be a unit attribute";
       if (verifyValueType && !resTy.isa<LLVMPointerType>())
         return op->emitError()
                << "llvm.noalias attribute attached to non-pointer result";
       return success();
     }
+    if (name == LLVMDialect::getReadonlyAttrName()) {
+      if (!attrValue.isa<UnitAttr>())
+        return op->emitError() << "expected llvm.readonly result attribute to "
+                                  "be a unit attribute";
+      if (verifyValueType && !resTy.isa<LLVMPointerType>())
+        return op->emitError()
+               << "llvm.readonly attribute attached to non-pointer result";
+      return success();
+    }
     if (name == LLVMDialect::getNoUndefAttrName()) {
       if (!attrValue.isa<UnitAttr>())
         return op->emitError() << "expected llvm.noundef result attribute to "
                                   "be a unit attribute";
       return success();
     }
     if (name == LLVMDialect::getSExtAttrName()) {
       if (!attrValue.isa<UnitAttr>())

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

for (auto [mlirArgTy, llvmArg] :
               argIdx, LLVMDialect::getNoAliasAttrName())) {
         // NB: Attribute already verified to be boolean, so check if we can
         // indeed attach the attribute to this argument, based on its type.
         if (!mlirArgTy.isa<LLVM::LLVMPointerType>())
           return function.emitError(
               "llvm.noalias attribute attached to LLVM non-pointer argument");
         llvmArg.addAttr(llvm::Attribute::AttrKind::NoAlias);
       }
+      if (auto attr = function.getArgAttrOfType<UnitAttr>(
+              argIdx, LLVMDialect::getReadonlyAttrName())) {
+        if (!mlirArgTy.isa<LLVM::LLVMPointerType>())
+          return function.emitError(
+              "llvm.readonly attribute attached to LLVM non-pointer argument");
+        llvmArg.addAttr(llvm::Attribute::AttrKind::ReadOnly);
+      }
 
       if (auto attr = function.getArgAttrOfType<IntegerAttr>(
               argIdx, LLVMDialect::getAlignAttrName())) {
         // NB: Attribute already verified to be int, so check if we can indeed
         // attach the attribute to this argument, based on its type.
         if (!mlirArgTy.isa<LLVM::LLVMPointerType>())
           return function.emitError(
               "llvm.align attribute attached to LLVM non-pointer argument");

mlir/test/Target/LLVMIR/llvmir-invalid.mlir

 
 // -----
 
 llvm.func @stepvector_intr_wrong_type() -> vector<7xf32> {
   // expected-error @below{{op result #0 must be LLVM dialect-compatible vector of signless integer, but got 'vector<7xf32>'}}
   %0 = llvm.intr.experimental.stepvector : vector<7xf32>
   llvm.return %0 : vector<7xf32>
 }
+
+// -----
+
+// expected-error @below{{llvm.readonly attribute attached to LLVM non-pointer argument}}
+llvm.func @wrong_readonly_attribute(%vec : f32 {llvm.readonly}) {
+  llvm.return
+}

mlir/test/Target/LLVMIR/llvmir.mlir

 
 // -----
 
 // Function attributes: readnone
 
 // CHECK: declare void @readnone_function() #[[ATTR:[0-9]+]]
 // CHECK: attributes #[[ATTR]] = { memory(none) }
 llvm.func @readnone_function() attributes {llvm.readnone}
+
+// -----
+// CHECK: declare void @readonly_function([[PTR:.+]] readonly)
+llvm.func @readonly_function(%arg0: !llvm.ptr<f32> {llvm.readonly})