[nightmarish hacks within] Lower UB checks as a new kind of intrinsic, not calls

compiler/rustc_borrowck/src/lib.rs

@@ -628,6 +628,10 @@ impl<'cx, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx, R> for MirBorro
                 NonDivergingIntrinsic::CopyNonOverlapping(..) => span_bug!(
                     span,
                     "Unexpected CopyNonOverlapping, should only appear after lower_intrinsics",
+                ),
+                NonDivergingIntrinsic::UbCheck { .. } => span_bug!(
+                    span,
+                    "Unexpected UbCheck, should only appear after lower_intrinsics",
                 )
             }
             // Only relevant for mir typeck

compiler/rustc_borrowck/src/polonius/loan_invalidations.rs

@@ -62,6 +62,18 @@ impl<'cx, 'tcx> Visitor<'tcx> for LoanInvalidationsGenerator<'cx, 'tcx> {
                 self.consume_operand(location, dst);
                 self.consume_operand(location, count);
             }
+            StatementKind::Intrinsic(box NonDivergingIntrinsic::UbCheck {
+                kind: _,
+                func,
+                args,
+                destination,
+                source_info: _,
+                fn_span: _,
+            }) => {
+                self.consume_operand(location, func);
+                self.consume_operand(location, args);
+                self.mutate_place(location, *destination, Shallow(None));
+            }
             // Only relevant for mir typeck
             StatementKind::AscribeUserType(..)
             // Only relevant for liveness and unsafeck

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1367,6 +1367,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     stmt.source_info.span,
                     "Unexpected NonDivergingIntrinsic::CopyNonOverlapping, should only appear after lowering_intrinsics",
                 ),
+                NonDivergingIntrinsic::UbCheck { .. } => span_bug!(
+                    stmt.source_info.span,
+                    "Unexpected NonDivergingIntrinsic::UbCheck, should only appear after lowering_intrinsics",
+                ),
             },
             StatementKind::FakeRead(..)
             | StatementKind::StorageLive(..)
@@ -2001,7 +2005,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     ConstraintCategory::SizedBound,
                 );
             }
-            &Rvalue::NullaryOp(NullOp::DebugAssertions, _) => {}
 
             Rvalue::ShallowInitBox(operand, ty) => {
                 self.check_operand(operand, location);

compiler/rustc_codegen_cranelift/src/base.rs

@@ -767,15 +767,6 @@ fn codegen_stmt<'tcx>(
                         NullOp::OffsetOf(fields) => {
                             layout.offset_of_subfield(fx, fields.iter()).bytes()
                         }
-                        NullOp::DebugAssertions => {
-                            let val = fx.tcx.sess.opts.debug_assertions;
-                            let val = CValue::by_val(
-                                fx.bcx.ins().iconst(types::I8, i64::try_from(val).unwrap()),
-                                fx.layout_of(fx.tcx.types.bool),
-                            );
-                            lval.write_cvalue(fx, val);
-                            return;
-                        }
                     };
                     let val = CValue::by_val(
                         fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(val).unwrap()),
@@ -845,6 +836,9 @@ fn codegen_stmt<'tcx>(
                 };
                 fx.bcx.call_memcpy(fx.target_config, dst, src, bytes);
             }
+            NonDivergingIntrinsic::UbCheck { .. } => {
+                todo!() // FIXME
+            }
         },
     }
 }

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -504,6 +504,7 @@ pub(crate) fn mir_operand_get_const_val<'tcx>(
                         StatementKind::Intrinsic(ref intrinsic) => match **intrinsic {
                             NonDivergingIntrinsic::CopyNonOverlapping(..) => return None,
                             NonDivergingIntrinsic::Assume(..) => {}
+                            NonDivergingIntrinsic::UbCheck { .. } => {}
                         },
                         // conservative handling
                         StatementKind::Assign(_)

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -28,19 +28,19 @@ use std::cmp;
 // can happen when BB jumps directly to its successor and the successor has no
 // other predecessors.
 #[derive(Debug, PartialEq)]
-enum MergingSucc {
+pub(crate) enum MergingSucc {
     False,
     True,
 }
 
 /// Used by `FunctionCx::codegen_terminator` for emitting common patterns
 /// e.g., creating a basic block, calling a function, etc.
-struct TerminatorCodegenHelper<'tcx> {
-    bb: mir::BasicBlock,
-    terminator: &'tcx mir::Terminator<'tcx>,
+pub(crate) struct TerminatorCodegenHelper<'term, 'tcx> {
+    pub(crate) bb: mir::BasicBlock,
+    pub(crate) terminator: &'term mir::Terminator<'tcx>,
 }
 
-impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
+impl<'term, 'a, 'tcx> TerminatorCodegenHelper<'term, 'tcx> {
     /// Returns the appropriate `Funclet` for the current funclet, if on MSVC,
     /// either already previously cached, or newly created, by `landing_pad_for`.
     fn funclet<'b, Bx: BuilderMethods<'a, 'tcx>>(
@@ -98,6 +98,10 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
         fx: &mut FunctionCx<'a, 'tcx, Bx>,
         target: mir::BasicBlock,
     ) -> (bool, bool) {
+        if self.bb > fx.mir.basic_blocks.len().into() {
+            return (false, false);
+        }
+
         if let Some(ref cleanup_kinds) = fx.cleanup_kinds {
             let funclet_bb = cleanup_kinds[self.bb].funclet_bb(self.bb);
             let target_funclet = cleanup_kinds[target].funclet_bb(target);
@@ -226,8 +230,10 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
             MergingSucc::False
         } else {
             let llret = bx.call(fn_ty, fn_attrs, Some(fn_abi), fn_ptr, llargs, self.funclet(fx));
-            if fx.mir[self.bb].is_cleanup {
-                bx.apply_attrs_to_cleanup_callsite(llret);
+            if let Some(bb) = fx.mir.basic_blocks.get(self.bb) {
+                if bb.is_cleanup {
+                    bx.apply_attrs_to_cleanup_callsite(llret);
+                }
             }
 
             if let Some((ret_dest, target)) = destination {
@@ -296,7 +302,11 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
 /// Codegen implementations for some terminator variants.
 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     /// Generates code for a `Resume` terminator.
-    fn codegen_resume_terminator(&mut self, helper: TerminatorCodegenHelper<'tcx>, bx: &mut Bx) {
+    fn codegen_resume_terminator(
+        &mut self,
+        helper: TerminatorCodegenHelper<'_, 'tcx>,
+        bx: &mut Bx,
+    ) {
         if let Some(funclet) = helper.funclet(self) {
             bx.cleanup_ret(funclet, None);
         } else {
@@ -313,7 +323,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
     fn codegen_switchint_terminator(
         &mut self,
-        helper: TerminatorCodegenHelper<'tcx>,
+        helper: TerminatorCodegenHelper<'_, 'tcx>,
         bx: &mut Bx,
         discr: &mir::Operand<'tcx>,
         targets: &SwitchTargets,
@@ -451,7 +461,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     #[tracing::instrument(level = "trace", skip(self, helper, bx))]
     fn codegen_drop_terminator(
         &mut self,
-        helper: TerminatorCodegenHelper<'tcx>,
+        helper: TerminatorCodegenHelper<'_, 'tcx>,
         bx: &mut Bx,
         location: mir::Place<'tcx>,
         target: mir::BasicBlock,
@@ -569,7 +579,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
     fn codegen_assert_terminator(
         &mut self,
-        helper: TerminatorCodegenHelper<'tcx>,
+        helper: TerminatorCodegenHelper<'_, 'tcx>,
         bx: &mut Bx,
         terminator: &mir::Terminator<'tcx>,
         cond: &mir::Operand<'tcx>,
@@ -649,7 +659,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
     fn codegen_terminate_terminator(
         &mut self,
-        helper: TerminatorCodegenHelper<'tcx>,
+        helper: TerminatorCodegenHelper<'_, 'tcx>,
         bx: &mut Bx,
         terminator: &mir::Terminator<'tcx>,
         reason: UnwindTerminateReason,
@@ -678,7 +688,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     /// Returns `Some` if this is indeed a panic intrinsic and codegen is done.
     fn codegen_panic_intrinsic(
         &mut self,
-        helper: &TerminatorCodegenHelper<'tcx>,
+        helper: &TerminatorCodegenHelper<'_, 'tcx>,
         bx: &mut Bx,
         intrinsic: Option<Symbol>,
         instance: Option<Instance<'tcx>>,
@@ -744,9 +754,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         }
     }
 
-    fn codegen_call_terminator(
+    pub(crate) fn codegen_call_terminator(
         &mut self,
-        helper: TerminatorCodegenHelper<'tcx>,
+        helper: TerminatorCodegenHelper<'_, 'tcx>,
         bx: &mut Bx,
         terminator: &mir::Terminator<'tcx>,
         func: &mir::Operand<'tcx>,
@@ -1068,7 +1078,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
     fn codegen_asm_terminator(
         &mut self,
-        helper: TerminatorCodegenHelper<'tcx>,
+        helper: TerminatorCodegenHelper<'_, 'tcx>,
         bx: &mut Bx,
         terminator: &mir::Terminator<'tcx>,
         template: &[ast::InlineAsmTemplatePiece],

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -684,10 +684,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         let val = layout.offset_of_subfield(bx.cx(), fields.iter()).bytes();
                         bx.cx().const_usize(val)
                     }
-                    mir::NullOp::DebugAssertions => {
-                        let val = bx.tcx().sess.opts.debug_assertions;
-                        bx.cx().const_bool(val)
-                    }
                 };
                 let tcx = self.cx.tcx();
                 OperandRef {

compiler/rustc_codegen_ssa/src/mir/statement.rs

@@ -1,9 +1,11 @@
 use rustc_middle::mir;
 use rustc_middle::mir::NonDivergingIntrinsic;
 use rustc_session::config::OptLevel;
+use rustc_span::source_map::respan;
 
 use super::FunctionCx;
 use super::LocalRef;
+use crate::mir::block::TerminatorCodegenHelper;
 use crate::traits::*;
 
 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
@@ -90,6 +92,44 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let src = src_val.immediate();
                 bx.memcpy(dst, align, src, align, bytes, crate::MemFlags::empty());
             }
+            mir::StatementKind::Intrinsic(box NonDivergingIntrinsic::UbCheck {
+                kind: _,
+                ref func,
+                ref args,
+                destination,
+                fn_span,
+                source_info,
+            }) => {
+                if bx.tcx().sess.opts.debug_assertions {
+                    let bb = mir::BasicBlock::MAX;
+                    let args = vec![respan(source_info.span, args.clone())];
+                    let terminator = mir::Terminator {
+                        source_info,
+                        kind: mir::TerminatorKind::Call {
+                            func: func.clone(),
+                            args: args.clone(),
+                            destination,
+                            target: Some(bb),
+                            unwind: mir::UnwindAction::Unreachable,
+                            call_source: mir::CallSource::Normal,
+                            fn_span,
+                        },
+                    };
+                    let helper = TerminatorCodegenHelper { bb, terminator: &terminator };
+                    self.codegen_call_terminator(
+                        helper,
+                        bx,
+                        &terminator,
+                        func,
+                        args.as_slice(),
+                        destination,
+                        Some(bb),
+                        mir::UnwindAction::Unreachable,
+                        fn_span,
+                        true, // mergeable_succ
+                    );
+                }
+            }
             mir::StatementKind::FakeRead(..)
             | mir::StatementKind::Retag { .. }
             | mir::StatementKind::AscribeUserType(..)

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -317,6 +317,7 @@ impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
                         dest,
                         ret,
                         mir::UnwindAction::Unreachable,
+                        false,
                     )?;
                     Ok(ControlFlow::Break(()))
                 } else {

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -155,6 +155,9 @@ pub enum StackPopCleanup {
     /// wants them leaked to intern what they need (and just throw away
     /// the entire `ecx` when it is done).
     Root { cleanup: bool },
+
+    /// FIXME: We're returning from a UbCheck call, don't do anything.
+    Nothing,
 }
 
 /// State of a local variable including a memoized layout
@@ -928,6 +931,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let cleanup = match return_to_block {
             StackPopCleanup::Goto { .. } => true,
             StackPopCleanup::Root { cleanup, .. } => cleanup,
+            StackPopCleanup::Nothing => true,
         };
         if cleanup {
             // We need to take the locals out, since we need to mutate while iterating.
@@ -964,6 +968,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 StackPopCleanup::Root { .. } => {
                     panic!("encountered StackPopCleanup::Root when unwinding!")
                 }
+                StackPopCleanup::Nothing => {
+                    panic!("encountered StackPopCleanup::Nothing when unwinding!")
+                }
             };
             // This must be the very last thing that happens, since it can in fact push a new stack frame.
             self.unwind_to_block(unwind)
@@ -978,6 +985,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     );
                     Ok(())
                 }
+                StackPopCleanup::Nothing => {
+                    // Advance the program counter.
+                    self.frame_mut().loc.as_mut().left().unwrap().statement_index += 1;
+                    Ok(())
+                }
             }
         }
     }