diff options
Diffstat (limited to 'compiler/rustc_codegen_ssa/src/glue.rs')
| -rw-r--r-- | compiler/rustc_codegen_ssa/src/glue.rs | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/compiler/rustc_codegen_ssa/src/glue.rs b/compiler/rustc_codegen_ssa/src/glue.rs index 694f5434e9a..e6f402ef19d 100644 --- a/compiler/rustc_codegen_ssa/src/glue.rs +++ b/compiler/rustc_codegen_ssa/src/glue.rs @@ -39,7 +39,12 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( // The info in this case is the length of the str, so the size is that // times the unit size. ( - bx.mul(info.unwrap(), bx.const_usize(unit.size.bytes())), + // All slice sizes must fit into `isize`, so this multiplication cannot (signed) wrap. + // NOTE: ideally, we want the effects of both `unchecked_smul` and `unchecked_umul` + // (resulting in `mul nsw nuw` in LLVM IR), since we know that the multiplication + // cannot signed wrap, and that both operands are non-negative. But at the time of writing, + // `BuilderMethods` can't do this, and it doesn't seem to enable any further optimizations. + bx.unchecked_smul(info.unwrap(), bx.const_usize(unit.size.bytes())), bx.const_usize(unit.align.abi.bytes()), ) } |