diff options
Diffstat (limited to 'compiler/rustc_codegen_ssa/src/base.rs')
| -rw-r--r-- | compiler/rustc_codegen_ssa/src/base.rs | 35 |
1 files changed, 31 insertions, 4 deletions
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs index f7f2bfca838..410b5d27c57 100644 --- a/compiler/rustc_codegen_ssa/src/base.rs +++ b/compiler/rustc_codegen_ssa/src/base.rs @@ -5,7 +5,7 @@ use crate::back::write::{ compute_per_cgu_lto_type, start_async_codegen, submit_codegened_module_to_llvm, submit_post_lto_module_to_llvm, submit_pre_lto_module_to_llvm, ComputedLtoType, OngoingCodegen, }; -use crate::common::{IntPredicate, RealPredicate, TypeKind}; +use crate::common::{self, IntPredicate, RealPredicate, TypeKind}; use crate::errors; use crate::meth; use crate::mir; @@ -33,7 +33,7 @@ use rustc_middle::mir::mono::{CodegenUnit, CodegenUnitNameBuilder, MonoItem}; use rustc_middle::query::Providers; use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf, TyAndLayout}; use rustc_middle::ty::{self, Instance, Ty, TyCtxt}; -use rustc_session::config::{self, CrateType, EntryFnType, OutputType}; +use rustc_session::config::{self, CrateType, EntryFnType, OptLevel, OutputType}; use rustc_session::Session; use rustc_span::symbol::sym; use rustc_span::Symbol; @@ -300,14 +300,35 @@ pub fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( } } -pub fn cast_shift_expr_rhs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( +/// Returns `rhs` sufficiently masked, truncated, and/or extended so that +/// it can be used to shift `lhs`. +/// +/// Shifts in MIR are all allowed to have mismatched LHS & RHS types. +/// The shift methods in `BuilderMethods`, however, are fully homogeneous +/// (both parameters and the return type are all the same type). +/// +/// If `is_unchecked` is false, this masks the RHS to ensure it stays in-bounds, +/// as the `BuilderMethods` shifts are UB for out-of-bounds shift amounts. +/// For 32- and 64-bit types, this matches the semantics +/// of Java. (See related discussion on #1877 and #10183.) +/// +/// If `is_unchecked` is true, this does no masking, and adds sufficient `assume` +/// calls or operation flags to preserve as much freedom to optimize as possible. +pub fn build_shift_expr_rhs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( bx: &mut Bx, lhs: Bx::Value, - rhs: Bx::Value, + mut rhs: Bx::Value, + is_unchecked: bool, ) -> Bx::Value { // Shifts may have any size int on the rhs let mut rhs_llty = bx.cx().val_ty(rhs); let mut lhs_llty = bx.cx().val_ty(lhs); + + let mask = common::shift_mask_val(bx, lhs_llty, rhs_llty, false); + if !is_unchecked { + rhs = bx.and(rhs, mask); + } + if bx.cx().type_kind(rhs_llty) == TypeKind::Vector { rhs_llty = bx.cx().element_type(rhs_llty) } @@ -317,6 +338,12 @@ pub fn cast_shift_expr_rhs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( let rhs_sz = bx.cx().int_width(rhs_llty); let lhs_sz = bx.cx().int_width(lhs_llty); if lhs_sz < rhs_sz { + if is_unchecked && bx.sess().opts.optimize != OptLevel::No { + // FIXME: Use `trunc nuw` once that's available + let inrange = bx.icmp(IntPredicate::IntULE, rhs, mask); + bx.assume(inrange); + } + bx.trunc(rhs, lhs_llty) } else if lhs_sz > rhs_sz { // We zero-extend even if the RHS is signed. So e.g. `(x: i32) << -1i8` will zero-extend the |