compiler/rustc_target/src/spec/x86_64_unknown_uefi.rs

   1 // This defines the amd64 target for UEFI systems as described in the UEFI specification. See the
   2 // uefi-base module for generic UEFI options. On x86_64 systems (mostly called "x64" in the spec)
   3 // UEFI systems always run in long-mode, have the interrupt-controller pre-configured and force a
   4 // single-CPU execution.
   5 // The win64 ABI is used. It differs from the sysv64 ABI, so we must use a windows target with
   6 // LLVM. "x86_64-unknown-windows" is used to get the minimal subset of windows-specific features.
   7
   8 use crate::spec::Target;
   9
  10 pub fn target() -> Target {
  11     let mut base = super::uefi_msvc_base::opts();
  12     base.cpu = "x86-64".into();
  13     base.max_atomic_width = Some(64);
  14
  15     // We disable MMX and SSE for now, even though UEFI allows using them. Problem is, you have to
  16     // enable these CPU features explicitly before their first use, otherwise their instructions
  17     // will trigger an exception. Rust does not inject any code that enables AVX/MMX/SSE
  18     // instruction sets, so this must be done by the firmware. However, existing firmware is known
  19     // to leave these uninitialized, thus triggering exceptions if we make use of them. Which is
  20     // why we avoid them and instead use soft-floats. This is also what GRUB and friends did so
  21     // far.
  22     //
  23     // If you initialize FP units yourself, you can override these flags with custom linker
  24     // arguments, thus giving you access to full MMX/SSE acceleration.
  25     base.features = "-mmx,-sse,+soft-float".into();
  26
  27     Target {
  28         llvm_target: "x86_64-unknown-windows".into(),
  29         pointer_width: 64,
  30         data_layout: "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
  31             .into(),
  32         arch: "x86_64".into(),
  33
  34         options: base,
  35     }
  36 }