I liked to build an image for an Intel G41 based mainboard and got that in the build log:
coreboot toolchain v1.52 June 11th, 2018 dsdt.aml 1525: CreateDwordField (PBUF, 0, PIO0) Remark 2089 - Object is not referenced ^ (Name [PIO0] is within a method [_GTM])
dsdt.aml 1526: CreateDwordField (PBUF, 4, DMA0) Remark 2089 - Object is not referenced ^ (Name [DMA0] is within a method [_GTM])
dsdt.aml 1527: CreateDwordField (PBUF, 8, PIO1) Remark 2089 - Object is not referenced ^ (Name [PIO1] is within a method [_GTM])
dsdt.aml 1528: CreateDwordField (PBUF, 12, DMA1) Remark 2089 - Object is not referenced ^ (Name [DMA1] is within a method [_GTM])
dsdt.aml 1529: CreateDwordField (PBUF, 16, FLAG) Remark 2089 - Object is not referenced ^ (Name [FLAG] is within a method [_GTM])
dsdt.aml 1534: CreateDwordField (Arg0, 0, PIO0) Remark 2089 - Object is not referenced ^ (Name [PIO0] is within a method [_STM])
dsdt.aml 1535: CreateDwordField (Arg0, 4, DMA0) Remark 2089 - Object is not referenced ^ (Name [DMA0] is within a method [_STM])
dsdt.aml 1536: CreateDwordField (Arg0, 8, PIO1) Remark 2089 - Object is not referenced ^ (Name [PIO1] is within a method [_STM])
dsdt.aml 1537: CreateDwordField (Arg0, 12, DMA1) Remark 2089 - Object is not referenced ^ (Name [DMA1] is within a method [_STM])
dsdt.aml 1538: CreateDwordField (Arg0, 16, FLAG) Remark 2089 - Object is not referenced ^ (Name [FLAG] is within a method [_STM])
dsdt.aml 1562: CreateDwordField (PBUF, 0, PIO0) Remark 2089 - Object is not referenced ^ (Name [PIO0] is within a method [_GTM])
dsdt.aml 1563: CreateDwordField (PBUF, 4, DMA0) Remark 2089 - Object is not referenced ^ (Name [DMA0] is within a method [_GTM])
dsdt.aml 1564: CreateDwordField (PBUF, 8, PIO1) Remark 2089 - Object is not referenced ^ (Name [PIO1] is within a method [_GTM])
dsdt.aml 1565: CreateDwordField (PBUF, 12, DMA1) Remark 2089 - Object is not referenced ^ (Name [DMA1] is within a method [_GTM])
dsdt.aml 1566: CreateDwordField (PBUF, 16, FLAG) Remark 2089 - Object is not referenced ^ (Name [FLAG] is within a method [_GTM])
dsdt.aml 1571: CreateDwordField (Arg0, 0, PIO0) Remark 2089 - Object is not referenced ^ (Name [PIO0] is within a method [_STM])
dsdt.aml 1572: CreateDwordField (Arg0, 4, DMA0) Remark 2089 - Object is not referenced ^ (Name [DMA0] is within a method [_STM])
dsdt.aml 1573: CreateDwordField (Arg0, 8, PIO1) Remark 2089 - Object is not referenced ^ (Name [PIO1] is within a method [_STM])
dsdt.aml 1574: CreateDwordField (Arg0, 12, DMA1) Remark 2089 - Object is not referenced ^ (Name [DMA1] is within a method [_STM])
dsdt.aml 1575: CreateDwordField (Arg0, 16, FLAG) Remark 2089 - Object is not referenced ^ (Name [FLAG] is within a method [_STM])