Don't panic when the target is not supported by Cranelift

Author: bjorn3

src/lib.rs

@@ -217,18 +217,17 @@ impl CodegenBackend for CraneliftCodegenBackend {
     ) -> Result<(), ErrorReported> {
         use rustc_codegen_ssa::back::link::link_binary;
 
-        link_binary::<crate::archive::ArArchiveBuilder<'_>>(
-            sess,
-            &codegen_results,
-            outputs,
-        );
+        link_binary::<crate::archive::ArArchiveBuilder<'_>>(sess, &codegen_results, outputs);
 
         Ok(())
     }
 }
 
 fn target_triple(sess: &Session) -> target_lexicon::Triple {
-    sess.target.llvm_target.parse().unwrap()
+    match sess.target.llvm_target.parse() {
+        Ok(triple) => triple,
+        Err(err) => sess.fatal(&format!("target not recognized: {}", err)),
+    }
 }
 
 fn build_isa(sess: &Session, backend_config: &BackendConfig) -> Box<dyn isa::TargetIsa + 'static> {
@@ -278,15 +277,21 @@ fn build_isa(sess: &Session, backend_config: &BackendConfig) -> Box<dyn isa::Tar
         }
         Some(value) => {
             let mut builder =
-                cranelift_codegen::isa::lookup_variant(target_triple, variant).unwrap();
+                cranelift_codegen::isa::lookup_variant(target_triple.clone(), variant)
+                    .unwrap_or_else(|err| {
+                        sess.fatal(&format!("can't compile for {}: {}", target_triple, err));
+                    });
             if let Err(_) = builder.enable(value) {
-                sess.fatal("The specified target cpu isn't currently supported by Cranelift.");
+                sess.fatal("the specified target cpu isn't currently supported by Cranelift.");
             }
             builder
         }
         None => {
             let mut builder =
-                cranelift_codegen::isa::lookup_variant(target_triple.clone(), variant).unwrap();
+                cranelift_codegen::isa::lookup_variant(target_triple.clone(), variant)
+                    .unwrap_or_else(|err| {
+                        sess.fatal(&format!("can't compile for {}: {}", target_triple, err));
+                    });
             if target_triple.architecture == target_lexicon::Architecture::X86_64 {
                 // Don't use "haswell" as the default, as it implies `has_lzcnt`.
                 // macOS CI is still at Ivy Bridge EP, so `lzcnt` is interpreted as `bsr`.