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[MLIR][LLVM] Don't use void return type in MLIR APIs. #4

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[MLIR][LLVM] Don't use void return type in MLIR APIs. #4

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8 changes: 6 additions & 2 deletions mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
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Expand Up @@ -1514,14 +1514,18 @@ def LLVM_LLVMFuncOp : LLVM_Op<"func", [
ArrayRef<Type> getArgumentTypes() { return getFunctionType().getParams(); }

/// Returns the result types of this function.
ArrayRef<Type> getResultTypes() { return getFunctionType().getReturnTypes(); }
ArrayRef<Type> getResultTypes() {
if (getFunctionType().getReturnType().isa<LLVM::LLVMVoidType>())
return {};
return getFunctionType().getReturnTypes();
}

/// Returns the callable region, which is the function body. If the function
/// is external, returns null.
Region *getCallableRegion();

/// Returns the callable result type, which is the function return type.
ArrayRef<Type> getCallableResults() { return getFunctionType().getReturnTypes(); }
ArrayRef<Type> getCallableResults() { return getResultTypes(); }

}];

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11 changes: 10 additions & 1 deletion mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp
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Expand Up @@ -2044,7 +2044,16 @@ buildLLVMFunctionType(OpAsmParser &parser, SMLoc loc, ArrayRef<Type> inputs,
llvmInputs.push_back(t);
}

// No output is denoted as "void" in LLVM type system.
// The void return type is an internal implementation detail that should not
// be expressed explicitly on the IR. This is symmetric to the printer, which
// does not print the implicit void return type.
if (!outputs.empty() && outputs.front().isa<LLVMVoidType>()) {
parser.emitError(loc, "failed to construct function type: void return type "
"should not be passed explicitly");
return {};
}

// Set implicit void type to represent no return value.
Type llvmOutput =
outputs.empty() ? LLVMVoidType::get(b.getContext()) : outputs.front();
if (!isCompatibleType(llvmOutput)) {
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4 changes: 2 additions & 2 deletions mlir/test/Dialect/LLVMIR/func.mlir
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Expand Up @@ -256,8 +256,8 @@ module {
// -----

module {
// expected-error@+1 {{cannot attach result attributes to functions with a void return}}
llvm.func @variadic_def() -> (!llvm.void {llvm.noundef})
// expected-error@+1 {{void return type should not be passed explicitly}}
llvm.func @variadic_def() -> (!llvm.void)
}

// -----
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4 changes: 2 additions & 2 deletions mlir/test/Target/LLVMIR/llvmir-types.mlir
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Expand Up @@ -5,7 +5,7 @@
//

// CHECK: declare void @return_void()
llvm.func @return_void() -> !llvm.void
llvm.func @return_void()
// CHECK: declare half @return_half()
llvm.func @return_half() -> f16
// CHECK: declare bfloat @return_bfloat()
Expand All @@ -28,7 +28,7 @@ llvm.func @return_x86_mmx() -> !llvm.x86_mmx
//

// CHECK: declare void @f_void_i32(i32)
llvm.func @f_void_i32(i32) -> !llvm.void
llvm.func @f_void_i32(i32)
// CHECK: declare i32 @f_i32_empty()
llvm.func @f_i32_empty() -> i32
// CHECK: declare i32 @f_i32_half_bfloat_float_double(half, bfloat, float, double)
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