Require either wrapping nullary intrinsincs in const blocks or explicitly deciding not to

Author: oli-obk

compiler/rustc_codegen_ssa/messages.ftl

@@ -260,6 +260,9 @@ codegen_ssa_self_contained_linker_missing = the self-contained linker was reques
 
 codegen_ssa_shuffle_indices_evaluation = could not evaluate shuffle_indices at compile time
 
+codegen_ssa_nullary_intrinsic_codegen = nullary intrinsics must either be in a const block or explicitly opted out because they are inherently runtime intrinsics
+    .label = `{name}` is a nullary intrinsic
+
 codegen_ssa_specify_libraries_to_link = use the `-l` flag to specify native libraries to link
 
 codegen_ssa_static_library_native_artifacts = Link against the following native artifacts when linking against this static library. The order and any duplication can be significant on some platforms.

compiler/rustc_codegen_ssa/src/errors.rs

@@ -761,6 +761,14 @@ pub(crate) struct ShuffleIndicesEvaluation {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_nullary_intrinsic_codegen)]
+pub(crate) struct NullaryIntrinsicCodegen {
+    #[primary_span]
+    pub span: Span,
+    pub name: Symbol,
+}
+
 #[derive(Diagnostic)]
 pub enum InvalidMonomorphization<'tcx> {
     #[diag(codegen_ssa_invalid_monomorphization_basic_integer_type, code = E0511)]

compiler/rustc_codegen_ssa/src/mir/intrinsic.rs

@@ -9,7 +9,7 @@ use super::FunctionCx;
 use super::operand::OperandRef;
 use super::place::PlaceRef;
 use crate::common::{AtomicRmwBinOp, SynchronizationScope};
-use crate::errors::InvalidMonomorphization;
+use crate::errors::{InvalidMonomorphization, NullaryIntrinsicCodegen};
 use crate::traits::*;
 use crate::{MemFlags, meth, size_of_val};
 
@@ -98,6 +98,26 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             discr.to_atomic_ordering()
         };
 
+        if args.is_empty() {
+            match name {
+                sym::abort
+                | sym::unreachable
+                | sym::cold_path
+                | sym::breakpoint
+                | sym::assert_zero_valid
+                | sym::assert_mem_uninitialized_valid
+                | sym::assert_inhabited
+                | sym::ub_checks
+                | sym::contract_checks
+                | sym::atomic_fence
+                | sym::caller_location => {}
+                _ => {
+                    bx.tcx().dcx().emit_err(NullaryIntrinsicCodegen { span, name });
+                    return Ok(());
+                }
+            }
+        }
+
         let llval = match name {
             sym::abort => {
                 bx.abort();

library/stdarch/crates/core_arch/src/lib.rs

@@ -31,6 +31,7 @@
     rtm_target_feature,
     allow_internal_unstable,
     decl_macro,
+    generic_arg_infer,
     asm_experimental_arch,
     x86_amx_intrinsics,
     f16,