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first determine if the variant is a niche-variant, then compute absol…

…ute variant
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RalfJung committed Sep 19, 2019
1 parent b21622c commit 1de533ac1a3bddd6bf61791f4ee6cf52cb186fdf
Showing with 17 additions and 15 deletions.
  1. +15 −14 src/librustc_mir/interpret/operand.rs
  2. +2 −1 src/librustc_mir/interpret/place.rs
@@ -1,7 +1,7 @@
//! Functions concerning immediate values and operands, and reading from operands.
//! All high-level functions to read from memory work on operands as sources.

use std::convert::TryInto;
use std::convert::{TryInto, TryFrom};

use rustc::{mir, ty};
use rustc::ty::layout::{
@@ -671,8 +671,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
ref niche_variants,
niche_start,
} => {
let variants_start = niche_variants.start().as_u32() as u128;
let variants_end = niche_variants.end().as_u32() as u128;
let variants_start = niche_variants.start().as_u32();
let variants_end = niche_variants.end().as_u32();
let raw_discr = raw_discr.not_undef().map_err(|_| {
err_unsup!(InvalidDiscriminant(ScalarMaybeUndef::Undef))
})?;
@@ -687,7 +687,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
(dataful_variant.as_u32() as u128, dataful_variant)
},
Ok(raw_discr) => {
// We need to use machine arithmetic to get the relative variant idx.
// We need to use machine arithmetic to get the relative variant idx:
// variant_index_relative = discr_val - niche_start_val
let discr_layout = self.layout_of(discr_layout.value.to_int_ty(*self.tcx))?;
let discr_val = ImmTy::from_uint(raw_discr, discr_layout);
let niche_start_val = ImmTy::from_uint(niche_start, discr_layout);
@@ -699,21 +700,21 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let variant_index_relative = variant_index_relative_val
.to_scalar()?
.assert_bits(discr_val.layout.size);
// Then computing the absolute variant idx should not overflow any more.
let variant_index = variants_start
.checked_add(variant_index_relative)
.expect("oveflow computing absolute variant idx");
// Check if this is in the range that indicates an actual discriminant.
if variants_start <= variant_index && variant_index <= variants_end {
let index = variant_index as usize;
assert_eq!(index as u128, variant_index);
assert!(index < rval.layout.ty
if variant_index_relative <= u128::from(variants_end - variants_start) {
let variant_index_relative = u32::try_from(variant_index_relative)
.expect("we checked that this fits into a u32");
// Then computing the absolute variant idx should not overflow any more.
let variant_index = variants_start
.checked_add(variant_index_relative)
.expect("oveflow computing absolute variant idx");
assert!((variant_index as usize) < rval.layout.ty
.ty_adt_def()
.expect("tagged layout for non adt")
.variants.len());
(variant_index, VariantIdx::from_usize(index))
(u128::from(variant_index), VariantIdx::from_u32(variant_index))
} else {
(dataful_variant.as_u32() as u128, dataful_variant)
(u128::from(dataful_variant.as_u32()), dataful_variant)
}
},
}
@@ -1064,7 +1064,8 @@ where
let variant_index_relative = variant_index.as_u32()
.checked_sub(variants_start)
.expect("overflow computing relative variant idx");
// We need to use machine arithmetic when taking into account `niche_start`.
// We need to use machine arithmetic when taking into account `niche_start`:
// discr_val = variant_index_relative + niche_start_val
let discr_layout = self.layout_of(discr_layout.value.to_int_ty(*self.tcx))?;
let niche_start_val = ImmTy::from_uint(niche_start, discr_layout);
let variant_index_relative_val =

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