// This defines the amd64 target for UEFI systems as described in the UEFI specification. See the
// uefi-base module for generic UEFI options. On x86_64 systems (mostly called "x64" in the spec)
// UEFI systems always run in long-mode, have the interrupt-controller pre-configured and force a
// single-CPU execution.
// The win64 ABI is used. It differs from the sysv64 ABI, so we must use a windows target with
// LLVM. "x86_64-unknown-windows" is used to get the minimal subset of windows-specific features.
use crate::spec::{LinkerFlavor, LldFlavor, Target, TargetResult};
pub fn target() -> TargetResult {
let mut base = super::uefi_base::opts();
base.cpu = "x86-64".to_string();
base.max_atomic_width = Some(64);
// We disable MMX and SSE for now, even though UEFI allows using them. Problem is, you have to
// enable these CPU features explicitly before their first use, otherwise their instructions
// will trigger an exception. Rust does not inject any code that enables AVX/MMX/SSE
// instruction sets, so this must be done by the firmware. However, existing firmware is known
// to leave these uninitialized, thus triggering exceptions if we make use of them. Which is
// why we avoid them and instead use soft-floats. This is also what GRUB and friends did so
// far.
// If you initialize FP units yourself, you can override these flags with custom linker
// arguments, thus giving you access to full MMX/SSE acceleration.
base.features = "-mmx,-sse,+soft-float".to_string();
// UEFI systems run without a host OS, hence we cannot assume any code locality. We must tell
// LLVM to expect code to reference any address in the address-space. The "large" code-model
// places no locality-restrictions, so it fits well here.
base.code_model = Some("large".to_string());
// UEFI mirrors the calling-conventions used on windows. In case of x86-64 this means small
// structs will be returned as int. This shouldn't matter much, since the restrictions placed
// by the UEFI specifications forbid any ABI to return structures.
base.abi_return_struct_as_int = true;
Ok(Target {
llvm_target: "x86_64-unknown-windows".to_string(),
target_endian: "little".to_string(),
target_pointer_width: "64".to_string(),
target_c_int_width: "32".to_string(),
data_layout: "e-m:w-i64:64-f80:128-n8:16:32:64-S128".to_string(),
target_os: "uefi".to_string(),
target_env: "".to_string(),
target_vendor: "unknown".to_string(),
arch: "x86_64".to_string(),
linker_flavor: LinkerFlavor::Lld(LldFlavor::Link),
options: base,
})
}