Add BPF target

This change adds the bpfel-unknown-none and bpfeb-unknown-none targets
which can be used to generate little endian and big endian BPF

compiler/rustc_target/src/abi/call/bpf.rs

@@ -0,0 +1,31 @@
+// see BPFCallingConv.td
+use crate::abi::call::{ArgAbi, FnAbi};
+
+fn classify_ret<Ty>(ret: &mut ArgAbi<'_, Ty>) {
+    if ret.layout.is_aggregate() || ret.layout.size.bits() > 64 {
+        ret.make_indirect();
+    } else {
+        ret.extend_integer_width_to(64);
+    }
+}
+
+fn classify_arg<Ty>(arg: &mut ArgAbi<'_, Ty>) {
+    if arg.layout.is_aggregate() || arg.layout.size.bits() > 64 {
+        arg.make_indirect();
+    } else {
+        arg.extend_integer_width_to(64);
+    }
+}
+
+pub fn compute_abi_info<Ty>(fn_abi: &mut FnAbi<'_, Ty>) {
+    if !fn_abi.ret.is_ignore() {
+        classify_ret(&mut fn_abi.ret);
+    }
+
+    for arg in &mut fn_abi.args {
+        if arg.is_ignore() {
+            continue;
+        }
+        classify_arg(arg);
+    }
+}

compiler/rustc_target/src/abi/call/mod.rs

@@ -6,6 +6,7 @@ mod aarch64;
 mod amdgpu;
 mod arm;
 mod avr;
+mod bpf;
 mod hexagon;
 mod mips;
 mod mips64;
@@ -654,6 +655,7 @@ impl<'a, Ty> FnAbi<'a, Ty> {
                 }
             }
             "asmjs" => wasm::compute_c_abi_info(cx, self),
+            "bpfel" | "bpfeb" => bpf::compute_abi_info(self),
             a => return Err(format!("unrecognized arch \"{}\" in target specification", a)),
         }
 

compiler/rustc_target/src/spec/bpf_base.rs

@@ -0,0 +1,37 @@
+use crate::spec::{LinkerFlavor, MergeFunctions, PanicStrategy, TargetOptions};
+use crate::{abi::Endian, spec::abi::Abi};
+
+pub fn opts(endian: Endian) -> TargetOptions {
+    TargetOptions {
+        endian,
+        linker_flavor: LinkerFlavor::BpfLinker,
+        atomic_cas: false,
+        executables: true,
+        dynamic_linking: true,
+        no_builtins: true,
+        panic_strategy: PanicStrategy::Abort,
+        position_independent_executables: true,
+        merge_functions: MergeFunctions::Disabled,
+        obj_is_bitcode: true,
+        requires_lto: false,
+        singlethread: true,
+        max_atomic_width: Some(64),
+        unsupported_abis: vec![
+            Abi::Cdecl,
+            Abi::Stdcall { unwind: false },
+            Abi::Stdcall { unwind: true },
+            Abi::Fastcall,
+            Abi::Vectorcall,
+            Abi::Thiscall { unwind: false },
+            Abi::Thiscall { unwind: true },
+            Abi::Aapcs,
+            Abi::Win64,
+            Abi::SysV64,
+            Abi::PtxKernel,
+            Abi::Msp430Interrupt,
+            Abi::X86Interrupt,
+            Abi::AmdGpuKernel,
+        ],
+        ..Default::default()
+    }
+}

compiler/rustc_target/src/spec/bpfeb_unknown_none.rs

@@ -0,0 +1,12 @@
+use crate::spec::Target;
+use crate::{abi::Endian, spec::bpf_base};
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "bpfeb".to_string(),
+        data_layout: "E-m:e-p:64:64-i64:64-i128:128-n32:64-S128".to_string(),
+        pointer_width: 64,
+        arch: "bpfeb".to_string(),
+        options: bpf_base::opts(Endian::Big),
+    }
+}

compiler/rustc_target/src/spec/bpfel_unknown_none.rs

@@ -0,0 +1,12 @@
+use crate::spec::Target;
+use crate::{abi::Endian, spec::bpf_base};
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "bpfel".to_string(),
+        data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".to_string(),
+        pointer_width: 64,
+        arch: "bpfel".to_string(),
+        options: bpf_base::opts(Endian::Little),
+    }
+}

compiler/rustc_target/src/spec/mod.rs

@@ -57,6 +57,7 @@ mod apple_base;
 mod apple_sdk_base;
 mod arm_base;
 mod avr_gnu_base;
+mod bpf_base;
 mod dragonfly_base;
 mod freebsd_base;
 mod fuchsia_base;
@@ -93,6 +94,7 @@ pub enum LinkerFlavor {
     Msvc,
     Lld(LldFlavor),
     PtxLinker,
+    BpfLinker,
 }
 
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
@@ -161,6 +163,7 @@ flavor_mappings! {
     ((LinkerFlavor::Ld), "ld"),
     ((LinkerFlavor::Msvc), "msvc"),
     ((LinkerFlavor::PtxLinker), "ptx-linker"),
+    ((LinkerFlavor::BpfLinker), "bpf-linker"),
     ((LinkerFlavor::Lld(LldFlavor::Wasm)), "wasm-ld"),
     ((LinkerFlavor::Lld(LldFlavor::Ld64)), "ld64.lld"),
     ((LinkerFlavor::Lld(LldFlavor::Ld)), "ld.lld"),
@@ -897,6 +900,9 @@ supported_targets! {
     ("aarch64_be-unknown-linux-gnu", aarch64_be_unknown_linux_gnu),
     ("aarch64-unknown-linux-gnu_ilp32", aarch64_unknown_linux_gnu_ilp32),
     ("aarch64_be-unknown-linux-gnu_ilp32", aarch64_be_unknown_linux_gnu_ilp32),
+
+    ("bpfeb-unknown-none", bpfeb_unknown_none),
+    ("bpfel-unknown-none", bpfel_unknown_none),
 }
 
 /// Everything `rustc` knows about how to compile for a specific target.