Allow building std with cranelift

- Don't pass llvm-specific args when using cranelift
- Don't use `asm` in compiler_builtins when using cranelift

Author: jyn514

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -567,7 +567,7 @@ fn codegen_msvc_try<'ll>(
         // module.
         //
         // When modifying, make sure that the type_name string exactly matches
-        // the one used in src/libpanic_unwind/seh.rs.
+        // the one used in library/panic_unwind/src/seh.rs.
         let type_info_vtable = bx.declare_global("??_7type_info@@6B@", bx.type_i8p());
         let type_name = bx.const_bytes(b"rust_panic\0");
         let type_info =

src/bootstrap/builder.rs

@@ -1853,7 +1853,10 @@ impl<'a> Builder<'a> {
             };
 
             if let Some(limit) = limit {
-                rustflags.arg(&format!("-Cllvm-args=-import-instr-limit={}", limit));
+                if stage == 0 || self.config.default_codegen_backend().unwrap_or_default() == "llvm"
+                {
+                    rustflags.arg(&format!("-Cllvm-args=-import-instr-limit={}", limit));
+                }
             }
         }
 

src/bootstrap/compile.rs

@@ -321,8 +321,15 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
         ""
     };
 
+    let mut features = String::new();
+
+    // Cranelift doesn't support `asm`.
+    if stage != 0 && builder.config.default_codegen_backend().unwrap_or_default() == "cranelift" {
+        features += " compiler-builtins-no-asm";
+    }
+
     if builder.no_std(target) == Some(true) {
-        let mut features = "compiler-builtins-mem".to_string();
+        features += " compiler-builtins-mem";
         if !target.starts_with("bpf") {
             features.push_str(compiler_builtins_c_feature);
         }
@@ -335,7 +342,7 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
             .arg("--features")
             .arg(features);
     } else {
-        let mut features = builder.std_features(target);
+        features += &builder.std_features(target);
         features.push_str(compiler_builtins_c_feature);
 
         cargo
@@ -754,7 +761,7 @@ pub fn rustc_cargo_env(builder: &Builder<'_>, cargo: &mut Cargo, target: TargetS
         .env("CFG_RELEASE_CHANNEL", &builder.config.channel)
         .env("CFG_VERSION", builder.rust_version());
 
-    if let Some(backend) = builder.config.rust_codegen_backends.get(0) {
+    if let Some(backend) = builder.config.default_codegen_backend() {
         cargo.env("CFG_DEFAULT_CODEGEN_BACKEND", backend);
     }
 

src/bootstrap/config.rs

@@ -1610,6 +1610,10 @@ impl Config {
         self.submodules.unwrap_or(rust_info.is_managed_git_subrepository())
     }
 
+    pub fn default_codegen_backend(&self) -> Option<Interned<String>> {
+        self.rust_codegen_backends.get(0).cloned()
+    }
+
     /// Returns the commit to download, or `None` if we shouldn't download CI artifacts.
     fn download_ci_rustc_commit(&self, download_rustc: Option<StringOrBool>) -> Option<String> {
         // If `download-rustc` is not set, default to rebuilding.

src/bootstrap/lib.rs

@@ -782,7 +782,7 @@ impl Build {
     /// Gets the space-separated set of activated features for the standard
     /// library.
     fn std_features(&self, target: TargetSelection) -> String {
-        let mut features = "panic-unwind".to_string();
+        let mut features = " panic-unwind".to_string();
 
         match self.config.llvm_libunwind(target) {
             LlvmLibunwind::InTree => features.push_str(" llvm-libunwind"),