Don't ICE on unimplemented call convs

src/abi/mod.rs

@@ -7,6 +7,7 @@ mod returning;
 use cranelift_module::ModuleError;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::ty::layout::FnAbiOf;
+use rustc_session::Session;
 use rustc_target::abi::call::{Conv, FnAbi};
 use rustc_target::spec::abi::Abi;
 
@@ -22,7 +23,7 @@ fn clif_sig_from_fn_abi<'tcx>(
     default_call_conv: CallConv,
     fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
 ) -> Signature {
-    let call_conv = conv_to_call_conv(fn_abi.conv, default_call_conv);
+    let call_conv = conv_to_call_conv(tcx.sess, fn_abi.conv, default_call_conv);
 
     let inputs = fn_abi.args.iter().map(|arg_abi| arg_abi.get_abi_param(tcx).into_iter()).flatten();
 
@@ -33,24 +34,30 @@ fn clif_sig_from_fn_abi<'tcx>(
     Signature { params, returns, call_conv }
 }
 
-pub(crate) fn conv_to_call_conv(c: Conv, default_call_conv: CallConv) -> CallConv {
+pub(crate) fn conv_to_call_conv(sess: &Session, c: Conv, default_call_conv: CallConv) -> CallConv {
     match c {
         Conv::Rust | Conv::C => default_call_conv,
         Conv::RustCold => CallConv::Cold,
         Conv::X86_64SysV => CallConv::SystemV,
         Conv::X86_64Win64 => CallConv::WindowsFastcall,
-        Conv::ArmAapcs
-        | Conv::CCmseNonSecureCall
+
+        // Should already get a back compat warning
+        Conv::X86Fastcall | Conv::X86Stdcall | Conv::X86ThisCall | Conv::X86VectorCall => {
+            default_call_conv
+        }
+
+        Conv::X86Intr => sess.fatal("x86-interrupt call conv not yet implemented"),
+
+        Conv::ArmAapcs => sess.fatal("aapcs call conv not yet implemented"),
+
+        Conv::CCmseNonSecureCall
         | Conv::Msp430Intr
         | Conv::PtxKernel
-        | Conv::X86Fastcall
-        | Conv::X86Intr
-        | Conv::X86Stdcall
-        | Conv::X86ThisCall
-        | Conv::X86VectorCall
         | Conv::AmdGpuKernel
         | Conv::AvrInterrupt
-        | Conv::AvrNonBlockingInterrupt => todo!("{:?}", c),
+        | Conv::AvrNonBlockingInterrupt => {
+            unreachable!("tried to use {c:?} call conv which only exists on an unsupported target");
+        }
     }
 }
 

src/main_shim.rs

@@ -64,6 +64,7 @@ pub(crate) fn maybe_create_entry_wrapper(
             ],
             returns: vec![AbiParam::new(m.target_config().pointer_type() /*isize*/)],
             call_conv: crate::conv_to_call_conv(
+                tcx.sess,
                 tcx.sess.target.options.entry_abi,
                 m.target_config().default_call_conv,
             ),