<commit_before>//! This module specifies the type based interner for constants.
//!
//! After a const evaluation has computed a value, before we destroy the const evaluator's session
//! memory, we need to extract all memory allocations to the global memory pool so they stay around.

use super::validity::RefTracking;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_hir as hir;
use rustc_middle::mir::interpret::InterpResult;
use rustc_middle::ty::{self, layout::TyAndLayout, Ty};
use rustc_target::abi::Size;

use rustc_ast::Mutability;

use super::{AllocId, Allocation, InterpCx, MPlaceTy, Machine, MemoryKind, Scalar, ValueVisitor};

pub trait CompileTimeMachine<'mir, 'tcx> = Machine<
    'mir,<commit_msg>explain why interning is not as trivial as it might seem<commit_after>//! This module specifies the type based interner for constants.
//!
//! After a const evaluation has computed a value, before we destroy the const evaluator's session
//! memory, we need to extract all memory allocations to the global memory pool so they stay around.
//!
//! In principle, this is not very complicated: we recursively walk the final value, follow all the
//! pointers, and move all reachable allocations to the global `tcx` memory. The only complication
//! is picking the right mutability for the allocations in a `static` initializer: we want to make
//! as many allocations as possible immutable so LLVM can put them into read-only memory. At the
//! same time, we need to make memory that could be mutated by the program mutable to avoid
//! incorrect compilations. To achieve this, we do a type-based traversal of the final value,
//! tracking mutable and shared references and `UnsafeCell` to determine the current mutability.
//! (In principle, we could skip this type-based part for `const` and promoteds, as they need to be
//! always immutable. At least for `const` however we use this opportunity to reject any `const`
//! that contains allocations whose mutability we cannot identify.)

use super::validity::RefTracking;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_hir as hir;
use rustc_middle::mir::interpret::InterpResult;
use rustc_middle::ty::{self, layout::TyAndLayout, Ty};
use rustc_target::abi::Size;

use rustc_ast::Mutability;

use super::{AllocId, Allocation, InterpCx, MPlaceTy, Machine, MemoryKind, Scalar, ValueVisitor};

pub trait CompileTimeMachine<'mir, 'tcx> = Machine<
    'mir,
{'fraction_non_alphanumeric': 0.09321340964840556, 'fraction_numerical': 0.0, 'mean_word_length': 5.24234693877551, 'pattern_counts': {'":': 0, '<': 7, '<?xml version=': 0, '>': 5, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '1549099', 'n_tokens_mistral': 694, 'n_tokens_neox': 676, 'n_words': 307}