1 files changed, 36 insertions, 0 deletions
diff --git a/compiler/rustc_target/src/spec/x86_64_unknown_uefi.rs b/compiler/rustc_target/src/spec/x86_64_unknown_uefi.rs
new file mode 100644
index 000000000..a7ae17839
--- /dev/null
+++ b/compiler/rustc_target/src/spec/x86_64_unknown_uefi.rs
@@ -0,0 +1,36 @@
+// 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::Target;
+
+pub fn target() -> Target {
+    let mut base = super::uefi_msvc_base::opts();
+    base.cpu = "x86-64".into();
+    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".into();
+
+    Target {
+        llvm_target: "x86_64-unknown-windows".into(),
+        pointer_width: 64,
+        data_layout: "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+            .into(),
+        arch: "x86_64".into(),
+
+        options: base,
+    }
+}