diff options
Diffstat (limited to 'compiler/rustc_mir_build/src/build/expr/as_rvalue.rs')
| -rw-r--r-- | compiler/rustc_mir_build/src/build/expr/as_rvalue.rs | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs index eece8684e..a5f6bb12e 100644 --- a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs +++ b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs @@ -10,8 +10,6 @@ use crate::build::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary}; use rustc_hir::lang_items::LangItem; use rustc_middle::middle::region; use rustc_middle::mir::interpret::Scalar; -use rustc_middle::mir::AssertKind; -use rustc_middle::mir::Place; use rustc_middle::mir::*; use rustc_middle::thir::*; use rustc_middle::ty::cast::{mir_cast_kind, CastTy}; @@ -600,10 +598,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> { BinOp::Shl | BinOp::Shr if self.check_overflow && ty.is_integral() => { // For an unsigned RHS, the shift is in-range for `rhs < bits`. // For a signed RHS, `IntToInt` cast to the equivalent unsigned - // type and do that same comparison. Because the type is the - // same size, there's no negative shift amount that ends up - // overlapping with valid ones, thus it catches negatives too. + // type and do that same comparison. + // A negative value will be *at least* 128 after the cast (that's i8::MIN), + // and 128 is an overflowing shift amount for all our currently existing types, + // so this cast can never make us miss an overflow. let (lhs_size, _) = ty.int_size_and_signed(self.tcx); + assert!(lhs_size.bits() <= 128); let rhs_ty = rhs.ty(&self.local_decls, self.tcx); let (rhs_size, _) = rhs_ty.int_size_and_signed(self.tcx); @@ -625,7 +625,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> { // This can't overflow because the largest shiftable types are 128-bit, // which fits in `u8`, the smallest possible `unsigned_ty`. - // (And `from_uint` will `bug!` if that's ever no longer true.) let lhs_bits = Operand::const_from_scalar( self.tcx, unsigned_ty, |