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Auto merge of #78407 - oli-obk:ub_checkable_ctfe, r=RalfJung,pnkfelix

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Make CTFE able to check for UB...

... by not doing any optimizations on the `const fn` MIR used in CTFE. This means we duplicate all `const fn`'s MIR now, once for CTFE, once for runtime. This PR is for checking the perf effect, so we have some data when talking about https://github.com/rust-lang/const-eval/blob/master/rfcs/0000-const-ub.md

To do this, we now have two queries for obtaining mir: `optimized_mir` and `mir_for_ctfe`. It is now illegal to invoke `optimized_mir` to obtain the MIR of a const/static item's initializer, an array length, an inline const expression or an enum discriminant initializer. For `const fn`, both `optimized_mir` and `mir_for_ctfe` work, the former returning the MIR that LLVM should use if the function is called at runtime. Similarly it is illegal to invoke `mir_for_ctfe` on regular functions.

This is all checked via appropriate assertions and I don't think it is easy to get wrong, as there should be no `mir_for_ctfe` calls outside the const evaluator or metadata encoding. Almost all rustc devs should keep using `optimized_mir` (or `instance_mir` for that matter).
This commit is contained in:
bors
2021-01-12 17:26:56 +00:00
parent 497c9a256b 53e3a23572
commit 704e47f78b
40 changed files with 560 additions and 224 deletions
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19
compiler/rustc_mir/src/transform/coverage/query.rs
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@@ -4,7 +4,7 @@ use rustc_middle::mir::coverage::*;
use rustc_middle::mir::visit::Visitor;
use rustc_middle::mir::{self, Coverage, CoverageInfo, Location};
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::TyCtxt;
use rustc_middle::ty::{self, TyCtxt};
use rustc_span::def_id::DefId;
/// The `query` provider for `CoverageInfo`, requested by `codegen_coverage()` (to inject each
@@ -112,7 +112,7 @@ impl Visitor<'_> for CoverageVisitor {
}
fn coverageinfo_from_mir<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> CoverageInfo {
let mir_body = tcx.optimized_mir(def_id);
let mir_body = mir_body(tcx, def_id);
let mut coverage_visitor = CoverageVisitor {
// num_counters always has at least the `ZERO` counter.
@@ -129,8 +129,7 @@ fn coverageinfo_from_mir<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> CoverageInfo
}
fn covered_file_name<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<Symbol> {
let mir_body = tcx.optimized_mir(def_id);
for bb_data in mir_body.basic_blocks().iter() {
for bb_data in mir_body(tcx, def_id).basic_blocks().iter() {
for statement in bb_data.statements.iter() {
if let StatementKind::Coverage(box ref coverage) = statement.kind {
if let Some(code_region) = coverage.code_region.as_ref() {
@@ -142,9 +141,17 @@ fn covered_file_name<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<Symbol> {
None
}
/// This function ensures we obtain the correct MIR for the given item irrespective of
/// whether that means const mir or runtime mir. For `const fn` this opts for runtime
/// mir.
fn mir_body<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx mir::Body<'tcx> {
let id = ty::WithOptConstParam::unknown(def_id);
let def = ty::InstanceDef::Item(id);
tcx.instance_mir(def)
}
fn covered_code_regions<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Vec<&'tcx CodeRegion> {
let mir_body: &'tcx mir::Body<'tcx> = tcx.optimized_mir(def_id);
mir_body
mir_body(tcx, def_id)
.basic_blocks()
.iter()
.map(|data| {