[MLIR] Adding 'inline_hint' attribute on LLMV::CallOp (#134582)

Addition of `inlinehint` attributes for CallOps in MLIR in order to be
able to say to a function call that the inlining is desirable without
having the attribute on the FuncOp.

Author: JDPailleux

mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td

@@ -749,6 +749,11 @@ def LLVM_CallOp : LLVM_MemAccessOpBase<"call",
     the LLVM function type that uses an explicit void type to model functions
     that do not return a value.
 
+    If this operatin has the `no_inline` attribute, then this specific function call 
+    will never be inlined. The opposite behavior will occur if the call has `always_inline` 
+    attribute. The `inline_hint` attribute indicates that it is desirable to inline 
+    this function call.
+
     Examples:
 
     ```mlir
@@ -778,16 +783,17 @@ def LLVM_CallOp : LLVM_MemAccessOpBase<"call",
       DefaultValuedAttr<CConv, "CConv::C">:$CConv,
       DefaultValuedAttr<TailCallKind, "TailCallKind::None">:$TailCallKind,
       OptionalAttr<LLVM_MemoryEffectsAttr>:$memory_effects,
-      OptionalAttr<UnitAttr>:$convergent,
-      OptionalAttr<UnitAttr>:$no_unwind,
-      OptionalAttr<UnitAttr>:$will_return,
+      UnitAttr:$convergent,
+      UnitAttr:$no_unwind,
+      UnitAttr:$will_return,
       VariadicOfVariadic<LLVM_Type, "op_bundle_sizes">:$op_bundle_operands,
       DenseI32ArrayAttr:$op_bundle_sizes,
       OptionalAttr<ArrayAttr>:$op_bundle_tags,
       OptionalAttr<DictArrayAttr>:$arg_attrs,
       OptionalAttr<DictArrayAttr>:$res_attrs,
-      OptionalAttr<UnitAttr>:$no_inline,
-      OptionalAttr<UnitAttr>:$always_inline);
+      UnitAttr:$no_inline,
+      UnitAttr:$always_inline,
+      UnitAttr:$inline_hint);
   // Append the aliasing related attributes defined in LLVM_MemAccessOpBase.
   let arguments = !con(args, aliasAttrs);
   let results = (outs Optional<LLVM_Type>:$result);

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

@@ -1032,7 +1032,8 @@ void CallOp::build(OpBuilder &builder, OperationState &state, TypeRange results,
         /*arg_attrs=*/nullptr, /*res_attrs=*/nullptr,
         /*access_groups=*/nullptr, /*alias_scopes=*/nullptr,
         /*noalias_scopes=*/nullptr, /*tbaa=*/nullptr,
-        /*no_inline=*/nullptr, /*always_inline=*/nullptr);
+        /*no_inline=*/nullptr, /*always_inline=*/nullptr,
+        /*inline_hint=*/nullptr);
 }
 
 void CallOp::build(OpBuilder &builder, OperationState &state,
@@ -1061,7 +1062,8 @@ void CallOp::build(OpBuilder &builder, OperationState &state,
         /*arg_attrs=*/nullptr, /*res_attrs=*/nullptr,
         /*access_groups=*/nullptr,
         /*alias_scopes=*/nullptr, /*noalias_scopes=*/nullptr, /*tbaa=*/nullptr,
-        /*no_inline=*/nullptr, /*always_inline=*/nullptr);
+        /*no_inline=*/nullptr, /*always_inline=*/nullptr,
+        /*inline_hint=*/nullptr);
 }
 
 void CallOp::build(OpBuilder &builder, OperationState &state,
@@ -1076,7 +1078,8 @@ void CallOp::build(OpBuilder &builder, OperationState &state,
         /*arg_attrs=*/nullptr, /*res_attrs=*/nullptr,
         /*access_groups=*/nullptr, /*alias_scopes=*/nullptr,
         /*noalias_scopes=*/nullptr, /*tbaa=*/nullptr,
-        /*no_inline=*/nullptr, /*always_inline=*/nullptr);
+        /*no_inline=*/nullptr, /*always_inline=*/nullptr,
+        /*inline_hint=*/nullptr);
 }
 
 void CallOp::build(OpBuilder &builder, OperationState &state, LLVMFuncOp func,
@@ -1091,7 +1094,8 @@ void CallOp::build(OpBuilder &builder, OperationState &state, LLVMFuncOp func,
         /*access_groups=*/nullptr, /*alias_scopes=*/nullptr,
         /*arg_attrs=*/nullptr, /*res_attrs=*/nullptr,
         /*noalias_scopes=*/nullptr, /*tbaa=*/nullptr,
-        /*no_inline=*/nullptr, /*always_inline=*/nullptr);
+        /*no_inline=*/nullptr, /*always_inline=*/nullptr,
+        /*inline_hint=*/nullptr);
 }
 
 CallInterfaceCallable CallOp::getCallableForCallee() {

mlir/lib/Target/LLVMIR/Dialect/LLVMIR/LLVMToLLVMIRTranslation.cpp

@@ -323,6 +323,8 @@ convertOperationImpl(Operation &opInst, llvm::IRBuilderBase &builder,
       call->addFnAttr(llvm::Attribute::NoInline);
     if (callOp.getAlwaysInlineAttr())
       call->addFnAttr(llvm::Attribute::AlwaysInline);
+    if (callOp.getInlineHintAttr())
+      call->addFnAttr(llvm::Attribute::InlineHint);
 
     if (failed(convertParameterAndResultAttrs(callOp, call, moduleTranslation)))
       return failure();

mlir/lib/Target/LLVMIR/ModuleImport.cpp

@@ -2362,6 +2362,7 @@ LogicalResult ModuleImport::convertCallAttributes(llvm::CallInst *inst,
   op.setNoInline(callAttrs.getFnAttr(llvm::Attribute::NoInline).isValid());
   op.setAlwaysInline(
       callAttrs.getFnAttr(llvm::Attribute::AlwaysInline).isValid());
+  op.setInlineHint(callAttrs.getFnAttr(llvm::Attribute::InlineHint).isValid());
 
   llvm::MemoryEffects memEffects = inst->getMemoryEffects();
   ModRefInfo othermem = convertModRefInfoFromLLVM(

mlir/test/Target/LLVMIR/Import/call-attributes.ll

@@ -23,3 +23,16 @@ define void @test_call_alwaysinline() {
 }
 
 attributes #0 = { alwaysinline }
+
+// -----
+
+declare void @f()
+
+; CHECK-LABEL: @test_call_inlinehint
+; CHECK: llvm.call @f() {inline_hint} : () -> ()
+define void @test_call_inlinehint() {
+  call void @f() #0 
+  ret void
+}
+
+attributes #0 = { inlinehint }

mlir/test/Target/LLVMIR/llvmir.mlir

@@ -2649,6 +2649,19 @@ llvm.func @always_inline_call() {
 // CHECK: #[[ATTRS]]
 // CHECK-SAME: alwaysinline
 
+// -----
+
+llvm.func @f()
+
+// CHECK-LABEL: @inline_hint_call
+// CHECK: call void @f() #[[ATTRS:[0-9]+]]
+llvm.func @inline_hint_call() {
+  llvm.call @f() {inline_hint} : () -> ()
+  llvm.return
+}
+
+// CHECK: #[[ATTRS]]
+// CHECK-SAME: inlinehint
 
 // -----