Emit erros when invalid config

Author: Sa4dUs

compiler/rustc_codegen_llvm/messages.ftl

@@ -17,6 +17,9 @@ codegen_llvm_lto_bitcode_from_rlib = failed to get bitcode from object file for
 codegen_llvm_mismatch_data_layout =
     data-layout for target `{$rustc_target}`, `{$rustc_layout}`, differs from LLVM target's `{$llvm_target}` default layout, `{$llvm_layout}`
 
+codegen_llvm_offload_without_enable = using the offload feature requires -Z offload=Enable
+codegen_llvm_offload_without_fat_lto = using the offload feature requires -C lto=fat
+
 codegen_llvm_parse_bitcode = failed to parse bitcode for LTO module
 codegen_llvm_parse_bitcode_with_llvm_err = failed to parse bitcode for LTO module: {$llvm_err}
 

compiler/rustc_codegen_llvm/src/errors.rs

@@ -36,6 +36,14 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for ParseTargetMachineConfig<'_> {
 #[diag(codegen_llvm_autodiff_without_enable)]
 pub(crate) struct AutoDiffWithoutEnable;
 
+#[derive(Diagnostic)]
+#[diag(codegen_llvm_offload_without_enable)]
+pub(crate) struct OffloadWithoutEnable;
+
+#[derive(Diagnostic)]
+#[diag(codegen_llvm_offload_without_fat_lto)]
+pub(crate) struct OffloadWithoutFatLTO;
+
 #[derive(Diagnostic)]
 #[diag(codegen_llvm_lto_bitcode_from_rlib)]
 pub(crate) struct LtoBitcodeFromRlib {

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -27,7 +27,7 @@ use crate::builder::Builder;
 use crate::builder::autodiff::{adjust_activity_to_abi, generate_enzyme_call};
 use crate::builder::gpu_offload::TgtOffloadEntry;
 use crate::context::CodegenCx;
-use crate::errors::AutoDiffWithoutEnable;
+use crate::errors::{AutoDiffWithoutEnable, OffloadWithoutEnable, OffloadWithoutFatLTO};
 use crate::llvm::{self, Metadata, Type, Value};
 use crate::type_of::LayoutLlvmExt;
 use crate::va_arg::emit_va_arg;
@@ -199,7 +199,20 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                 return Ok(());
             }
             sym::offload => {
-                // TODO(Sa4dUs): emit error when offload is not enabled
+                if !tcx
+                    .sess
+                    .opts
+                    .unstable_opts
+                    .offload
+                    .contains(&rustc_session::config::Offload::Enable)
+                {
+                    let _ = tcx.dcx().emit_almost_fatal(OffloadWithoutEnable);
+                }
+
+                if tcx.sess.lto() != rustc_session::config::Lto::Fat {
+                    let _ = tcx.dcx().emit_almost_fatal(OffloadWithoutFatLTO);
+                }
+
                 codegen_offload(self, tcx, instance, args);
                 return Ok(());
             }

compiler/rustc_middle/src/ty/offload_meta.rs

@@ -74,7 +74,7 @@ fn get_payload_size<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> u64 {
 }
 
 impl MappingFlags {
-    fn from_ty<'tcx>(_tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self {
+    fn from_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self {
         use rustc_ast::Mutability::*;
 
         match ty.kind() {
@@ -109,7 +109,11 @@ impl MappingFlags {
             | ty::Bound(_, _)
             | ty::Placeholder(_)
             | ty::Infer(_)
-            | ty::Error(_) => MappingFlags::TO, /* TODO(Sa4dUs): emit error */
+            | ty::Error(_) => {
+                tcx.dcx()
+                    .span_err(rustc_span::DUMMY_SP, format!("type `{ty:?}` cannot be offloaded"));
+                MappingFlags::empty()
+            }
         }
     }
 }

tests/ui/offload/check_config.fail.stderr

@@ -0,0 +1,6 @@
+error: using the offload feature requires -Z offload=Enable
+
+error: using the offload feature requires -C lto=fat
+
+error: aborting due to 2 previous errors
+

tests/ui/offload/check_config.rs

@@ -0,0 +1,21 @@
+//@ revisions: pass fail
+//@[pass] build-pass
+//@[fail] build-fail
+//@[pass] compile-flags: -Zunstable-options -Zoffload=Enable -Clto=fat --emit=metadata
+//@[fail] compile-flags: -Clto=thin
+
+//[fail]~? ERROR: using the offload feature requires -Z offload=Enable
+//[fail]~? ERROR: using the offload feature requires -C lto=fat
+
+#![feature(core_intrinsics)]
+
+fn main() {
+    let mut x = [3.0; 256];
+    kernel_1(&mut x);
+}
+
+fn kernel_1(x: &mut [f32; 256]) {
+    core::intrinsics::offload(_kernel_1, (x,))
+}
+
+fn _kernel_1(x: &mut [f32; 256]) {}