Prefer enum Endian instead of arbitrary String

Author: tesuji

compiler/rustc_codegen_llvm/src/va_arg.rs

@@ -52,7 +52,7 @@ fn emit_direct_ptr_va_arg(
     let next = bx.inbounds_gep(addr, &[full_direct_size]);
     bx.store(next, va_list_addr, bx.tcx().data_layout.pointer_align.abi);
 
-    if size.bytes() < slot_size.bytes() && &*bx.tcx().sess.target.target_endian == "big" {
+    if size.bytes() < slot_size.bytes() && bx.tcx().sess.target.target_endian.is_big() {
         let adjusted_size = bx.cx().const_i32((slot_size.bytes() - size.bytes()) as i32);
         let adjusted = bx.inbounds_gep(addr, &[adjusted_size]);
         (bx.bitcast(adjusted, bx.cx().type_ptr_to(llty)), addr_align)
@@ -105,7 +105,7 @@ fn emit_aapcs_va_arg(
     let mut end = bx.build_sibling_block("va_arg.end");
     let zero = bx.const_i32(0);
     let offset_align = Align::from_bytes(4).unwrap();
-    assert!(&*bx.tcx().sess.target.target_endian == "little");
+    assert!(bx.tcx().sess.target.target_endian.is_little());
 
     let gr_type = target_ty.is_any_ptr() || target_ty.is_integral();
     let (reg_off, reg_top_index, slot_size) = if gr_type {

compiler/rustc_session/src/config.rs

@@ -761,7 +761,7 @@ pub fn default_configuration(sess: &Session) -> CrateConfig {
         }
     }
     ret.insert((sym::target_arch, Some(Symbol::intern(arch))));
-    ret.insert((sym::target_endian, Some(Symbol::intern(end))));
+    ret.insert((sym::target_endian, Some(Symbol::intern(end.name()))));
     ret.insert((sym::target_pointer_width, Some(Symbol::intern(&wordsz))));
     ret.insert((sym::target_env, Some(Symbol::intern(env))));
     ret.insert((sym::target_vendor, Some(Symbol::intern(vendor))));

compiler/rustc_target/src/abi/mod.rs

@@ -4,11 +4,14 @@ pub use Primitive::*;
 use crate::spec::Target;
 
 use std::convert::{TryFrom, TryInto};
+use std::fmt;
 use std::num::NonZeroUsize;
 use std::ops::{Add, AddAssign, Deref, Mul, Range, RangeInclusive, Sub};
+use std::str::FromStr;
 
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_macros::HashStable_Generic;
+use rustc_serialize::json::{Json, ToJson};
 use rustc_span::Span;
 
 pub mod call;
@@ -152,15 +155,12 @@ impl TargetDataLayout {
         }
 
         // Perform consistency checks against the Target information.
-        let endian_str = match dl.endian {
-            Endian::Little => "little",
-            Endian::Big => "big",
-        };
-        if endian_str != target.target_endian {
+        if dl.endian != target.target_endian {
             return Err(format!(
                 "inconsistent target specification: \"data-layout\" claims \
-                                architecture is {}-endian, while \"target-endian\" is `{}`",
-                endian_str, target.target_endian
+                architecture is {}-endian, while \"target-endian\" is `{}`",
+                dl.endian.name(),
+                target.target_endian.name()
             ));
         }
 
@@ -234,6 +234,47 @@ pub enum Endian {
     Big,
 }
 
+impl Endian {
+    pub fn name(&self) -> &str {
+        match self {
+            Self::Little => "little",
+            Self::Big => "big",
+        }
+    }
+
+    pub fn is_big(&self) -> bool {
+        Self::Big == *self
+    }
+
+    pub fn is_little(&self) -> bool {
+        Self::Little == *self
+    }
+}
+
+impl fmt::Debug for Endian {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(self.name())
+    }
+}
+
+impl FromStr for Endian {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "little" => Ok(Self::Little),
+            "big" => Ok(Self::Big),
+            _ => Err(format!(r#"unknown endian: "{}""#, s)),
+        }
+    }
+}
+
+impl ToJson for Endian {
+    fn to_json(&self) -> Json {
+        Json::String(self.name().to_owned())
+    }
+}
+
 /// Size of a type in bytes.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)]
 #[derive(HashStable_Generic)]

compiler/rustc_target/src/spec/mod.rs

@@ -664,7 +664,7 @@ pub struct Target {
     /// Target triple to pass to LLVM.
     pub llvm_target: String,
     /// String to use as the `target_endian` `cfg` variable.
-    pub target_endian: String,
+    pub target_endian: crate::abi::Endian,
     /// Number of bits in a pointer. Influences the `target_pointer_width` `cfg` variable.
     pub pointer_width: u32,
     /// Width of c_int type
@@ -1143,7 +1143,7 @@ impl Target {
 
         let mut base = Target {
             llvm_target: get_req_field("llvm-target")?,
-            target_endian: get_req_field("target-endian")?,
+            target_endian: get_req_field("target-endian")?.parse()?,
             pointer_width: get_req_field("target-pointer-width")?
                 .parse::<u32>()
                 .map_err(|_| "target-pointer-width must be an integer".to_string())?,