diff options
| -rw-r--r-- | compiler/rustc_codegen_cranelift/src/discriminant.rs | 89 |
1 files changed, 0 insertions, 89 deletions
diff --git a/compiler/rustc_codegen_cranelift/src/discriminant.rs b/compiler/rustc_codegen_cranelift/src/discriminant.rs index f740945a03c..670384663e8 100644 --- a/compiler/rustc_codegen_cranelift/src/discriminant.rs +++ b/compiler/rustc_codegen_cranelift/src/discriminant.rs @@ -103,7 +103,6 @@ pub(crate) fn codegen_get_discriminant<'tcx>( } }; - let cast_to_size = dest_layout.layout.size(); let cast_to = fx.clif_type(dest_layout.ty).unwrap(); // Read the tag/niche-encoded discriminant from memory. @@ -122,21 +121,7 @@ pub(crate) fn codegen_get_discriminant<'tcx>( dest.write_cvalue(fx, res); } TagEncoding::Niche { untagged_variant, ref niche_variants, niche_start } => { - let tag_size = tag_scalar.size(fx); - let max_unsigned = tag_size.unsigned_int_max(); - let max_signed = tag_size.signed_int_max() as u128; - let min_signed = max_signed + 1; let relative_max = niche_variants.end().as_u32() - niche_variants.start().as_u32(); - let niche_end = niche_start.wrapping_add(relative_max as u128) & max_unsigned; - let range = tag_scalar.valid_range(fx); - - let sle = |lhs: u128, rhs: u128| -> bool { - // Signed and unsigned comparisons give the same results, - // except that in signed comparisons an integer with the - // sign bit set is less than one with the sign bit clear. - // Toggle the sign bit to do a signed comparison. - (lhs ^ min_signed) <= (rhs ^ min_signed) - }; // We have a subrange `niche_start..=niche_end` inside `range`. // If the value of the tag is inside this subrange, it's a @@ -153,45 +138,6 @@ pub(crate) fn codegen_get_discriminant<'tcx>( // } // However, we will likely be able to emit simpler code. - // Find the least and greatest values in `range`, considered - // both as signed and unsigned. - let (low_unsigned, high_unsigned) = - if range.start <= range.end { (range.start, range.end) } else { (0, max_unsigned) }; - let (low_signed, high_signed) = if sle(range.start, range.end) { - (range.start, range.end) - } else { - (min_signed, max_signed) - }; - - let niches_ule = niche_start <= niche_end; - let niches_sle = sle(niche_start, niche_end); - let cast_smaller = cast_to_size <= tag_size; - - // In the algorithm above, we can change - // cast(relative_tag) + niche_variants.start() - // into - // cast(tag + (niche_variants.start() - niche_start)) - // if either the casted type is no larger than the original - // type, or if the niche values are contiguous (in either the - // signed or unsigned sense). - let can_incr = cast_smaller || niches_ule || niches_sle; - - let data_for_boundary_niche = || -> Option<(IntCC, u128)> { - if !can_incr { - None - } else if niche_start == low_unsigned { - Some((IntCC::UnsignedLessThanOrEqual, niche_end)) - } else if niche_end == high_unsigned { - Some((IntCC::UnsignedGreaterThanOrEqual, niche_start)) - } else if niche_start == low_signed { - Some((IntCC::SignedLessThanOrEqual, niche_end)) - } else if niche_end == high_signed { - Some((IntCC::SignedGreaterThanOrEqual, niche_start)) - } else { - None - } - }; - let (is_niche, tagged_discr, delta) = if relative_max == 0 { // Best case scenario: only one tagged variant. This will // likely become just a comparison and a jump. @@ -206,41 +152,6 @@ pub(crate) fn codegen_get_discriminant<'tcx>( let tagged_discr = fx.bcx.ins().iconst(cast_to, niche_variants.start().as_u32() as i64); (is_niche, tagged_discr, 0) - } else if let Some((predicate, constant)) = data_for_boundary_niche() { - // The niche values are either the lowest or the highest in - // `range`. We can avoid the first subtraction in the - // algorithm. - // The algorithm is now this: - // is_niche = tag <= niche_end - // discr = if is_niche { - // cast(tag + (niche_variants.start() - niche_start)) - // } else { - // untagged_variant - // } - // (the first line may instead be tag >= niche_start, - // and may be a signed or unsigned comparison) - // The arithmetic must be done before the cast, so we can - // have the correct wrapping behavior. See issue #104519 for - // the consequences of getting this wrong. - let is_niche = codegen_icmp_imm(fx, predicate, tag, constant as i128); - let delta = (niche_variants.start().as_u32() as u128).wrapping_sub(niche_start); - let incr_tag = if delta == 0 { - tag - } else { - let delta = match fx.bcx.func.dfg.value_type(tag) { - types::I128 => { - let lsb = fx.bcx.ins().iconst(types::I64, delta as u64 as i64); - let msb = fx.bcx.ins().iconst(types::I64, (delta >> 64) as u64 as i64); - fx.bcx.ins().iconcat(lsb, msb) - } - ty => fx.bcx.ins().iconst(ty, delta as i64), - }; - fx.bcx.ins().iadd(tag, delta) - }; - - let cast_tag = clif_intcast(fx, incr_tag, cast_to, !niches_ule); - - (is_niche, cast_tag, 0) } else { // The special cases don't apply, so we'll have to go with // the general algorithm. |