Auto merge of #125359 - RalfJung:interpret-overflowing-ops, r=oli-obk

interpret: make overflowing binops just normal binops

Follow-up to https://github.com/rust-lang/rust/pull/125173 (Cc `@scottmcm)`

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -1,19 +1,22 @@
-use super::{AllocId, AllocRange, ConstAllocation, Pointer, Scalar};
+use std::borrow::Cow;
+use std::{any::Any, backtrace::Backtrace, fmt};
 
-use crate::error;
-use crate::mir::{ConstAlloc, ConstValue};
-use crate::ty::{self, layout, tls, Ty, TyCtxt, ValTree};
+use either::Either;
 
 use rustc_ast_ir::Mutability;
 use rustc_data_structures::sync::Lock;
 use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, ErrorGuaranteed, IntoDiagArg};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use rustc_session::CtfeBacktrace;
+use rustc_span::Symbol;
 use rustc_span::{def_id::DefId, Span, DUMMY_SP};
 use rustc_target::abi::{call, Align, Size, VariantIdx, WrappingRange};
 
-use std::borrow::Cow;
-use std::{any::Any, backtrace::Backtrace, fmt};
+use super::{AllocId, AllocRange, ConstAllocation, Pointer, Scalar};
+
+use crate::error;
+use crate::mir::{ConstAlloc, ConstValue};
+use crate::ty::{self, layout, tls, Ty, TyCtxt, ValTree};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
 pub enum ErrorHandled {
@@ -310,6 +313,10 @@ pub enum UndefinedBehaviorInfo<'tcx> {
     RemainderOverflow,
     /// Overflowing inbounds pointer arithmetic.
     PointerArithOverflow,
+    /// Overflow in arithmetic that may not overflow.
+    ArithOverflow { intrinsic: Symbol },
+    /// Shift by too much.
+    ShiftOverflow { intrinsic: Symbol, shift_amount: Either<u128, i128> },
     /// Invalid metadata in a wide pointer
     InvalidMeta(InvalidMetaKind),
     /// Reading a C string that does not end within its allocation.

compiler/rustc_middle/src/mir/tcx.rs

@@ -297,9 +297,11 @@ impl BorrowKind {
 impl BinOp {
     pub(crate) fn to_hir_binop(self) -> hir::BinOpKind {
         match self {
-            BinOp::Add => hir::BinOpKind::Add,
-            BinOp::Sub => hir::BinOpKind::Sub,
-            BinOp::Mul => hir::BinOpKind::Mul,
+            // HIR `+`/`-`/`*` can map to either of these MIR BinOp, depending
+            // on whether overflow checks are enabled or not.
+            BinOp::Add | BinOp::AddWithOverflow => hir::BinOpKind::Add,
+            BinOp::Sub | BinOp::SubWithOverflow => hir::BinOpKind::Sub,
+            BinOp::Mul | BinOp::MulWithOverflow => hir::BinOpKind::Mul,
             BinOp::Div => hir::BinOpKind::Div,
             BinOp::Rem => hir::BinOpKind::Rem,
             BinOp::BitXor => hir::BinOpKind::BitXor,
@@ -313,10 +315,8 @@ impl BinOp {
             BinOp::Gt => hir::BinOpKind::Gt,
             BinOp::Le => hir::BinOpKind::Le,
             BinOp::Ge => hir::BinOpKind::Ge,
+            // We don't have HIR syntax for these.
             BinOp::Cmp
-            | BinOp::AddWithOverflow
-            | BinOp::SubWithOverflow
-            | BinOp::MulWithOverflow
             | BinOp::AddUnchecked
             | BinOp::SubUnchecked
             | BinOp::MulUnchecked
@@ -338,6 +338,11 @@ impl BinOp {
         })
     }
 
+    /// Returns whether this is a `FooWithOverflow`
+    pub fn is_overflowing(self) -> bool {
+        self.overflowing_to_wrapping().is_some()
+    }
+
     /// If this is a `Foo`, return `Some(FooWithOverflow)`.
     pub fn wrapping_to_overflowing(self) -> Option<BinOp> {
         Some(match self {