Rollup merge of rust-lang#111772 - liushuyu:ubuntu/mips64-linkage, r=…

…jackh726

Fix linkage for large binaries on mips64 platforms

This pull request fixes the linkage for large binaries on mips64 platforms by enabling the `xgot` feature in LLVM.

It is well understood that the generated binary will gain a hefty performance penalty where the external symbol jumps now cost at least three instructions each.

Also, this pull request does not address the same issue on the mips32 counterparts (due to being unable to test the changes thoroughly).

Should fix rust-lang#52108

compiler/rustc_target/src/spec/mips64_unknown_linux_gnuabi64.rs

@@ -12,7 +12,7 @@ pub fn target() -> Target {
             endian: Endian::Big,
             // NOTE(mips64r2) matches C toolchain
             cpu: "mips64r2".into(),
-            features: "+mips64r2".into(),
+            features: "+mips64r2,+xgot".into(),
             max_atomic_width: Some(64),
             mcount: "_mcount".into(),
 

compiler/rustc_target/src/spec/mips64el_unknown_linux_gnuabi64.rs

@@ -10,7 +10,7 @@ pub fn target() -> Target {
             abi: "abi64".into(),
             // NOTE(mips64r2) matches C toolchain
             cpu: "mips64r2".into(),
-            features: "+mips64r2".into(),
+            features: "+mips64r2,+xgot".into(),
             max_atomic_width: Some(64),
             mcount: "_mcount".into(),
 

src/bootstrap/bootstrap.py

@@ -877,6 +877,12 @@ def build_bootstrap(self, color, verbose_count):
 
         # preserve existing RUSTFLAGS
         env.setdefault("RUSTFLAGS", "")
+        # we need to explicitly add +xgot here so that we can successfully bootstrap
+        # a usable stage1 compiler
+        # FIXME: remove this if condition on the next bootstrap bump
+        # cfg(bootstrap)
+        if self.build_triple().startswith('mips'):
+            env["RUSTFLAGS"] += " -Ctarget-feature=+xgot"
         target_features = []
         if self.get_toml("crt-static", build_section) == "true":
             target_features += ["+crt-static"]

tests/assembly/asm/mips-types.rs

@@ -72,7 +72,7 @@ macro_rules! check_reg { ($func:ident, $ty:ty, $reg:tt, $mov:literal) => {
 
 // mips32-LABEL: sym_static_32:
 // mips32: #APP
-// mips32: lw $3, %got(extern_static)
+// mips32: lw $3, %got(extern_static)($gp)
 // mips32: #NO_APP
 #[cfg(mips32)]
 #[no_mangle]
@@ -82,7 +82,7 @@ pub unsafe fn sym_static_32() {
 
 // mips32-LABEL: sym_fn_32:
 // mips32: #APP
-// mips32: lw $3, %got(extern_func)
+// mips32: lw $3, %got(extern_func)($gp)
 // mips32: #NO_APP
 #[cfg(mips32)]
 #[no_mangle]
@@ -92,7 +92,9 @@ pub unsafe fn sym_fn_32() {
 
 // mips64-LABEL: sym_static_64:
 // mips64: #APP
-// mips64: ld $3, %got_disp(extern_static)
+// mips64: lui    $3, %got_hi(extern_static)
+// mips64: daddu  $3, $3, $gp
+// mips64: ld     $3, %got_lo(extern_static)($3)
 // mips64: #NO_APP
 #[cfg(mips64)]
 #[no_mangle]
@@ -102,7 +104,9 @@ pub unsafe fn sym_static_64() {
 
 // mips64-LABEL: sym_fn_64:
 // mips64: #APP
-// mips64: ld $3, %got_disp(extern_func)
+// mips64: lui    $3, %got_hi(extern_func)
+// mips64: daddu  $3, $3, $gp
+// mips64: ld     $3, %got_lo(extern_func)($3)
 // mips64: #NO_APP
 #[cfg(mips64)]
 #[no_mangle]