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Don't compute optimized PointerKind for unoptimized builds

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This saves us both the Freeze/Unpin queries, and avoids placing
noalias attributes, which have a compile-time impact on LLVM
even in optnone builds (due to always_inline functions).
This commit is contained in:
Nikita Popov 2021-03-19 22:49:51 +01:00
parent 39ed64399e
commit 6ac229ca21
4 changed files with 27 additions and 20 deletions
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41
compiler/rustc_middle/src/ty/layout.rs
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@ -11,7 +11,7 @@ use rustc_hir as hir;
use rustc_hir::lang_items::LangItem; use rustc_hir::lang_items::LangItem;
use rustc_index::bit_set::BitSet; use rustc_index::bit_set::BitSet;
use rustc_index::vec::{Idx, IndexVec}; use rustc_index::vec::{Idx, IndexVec};
use rustc_session::{DataTypeKind, FieldInfo, SizeKind, VariantInfo}; use rustc_session::{config::OptLevel, DataTypeKind, FieldInfo, SizeKind, VariantInfo};
use rustc_span::symbol::{Ident, Symbol}; use rustc_span::symbol::{Ident, Symbol};
use rustc_span::DUMMY_SP; use rustc_span::DUMMY_SP;
use rustc_target::abi::call::{ use rustc_target::abi::call::{
@ -2318,23 +2318,30 @@ where
ty::Ref(_, ty, mt) if offset.bytes() == 0 => { ty::Ref(_, ty, mt) if offset.bytes() == 0 => {
let address_space = addr_space_of_ty(ty); let address_space = addr_space_of_ty(ty);
let tcx = cx.tcx(); let tcx = cx.tcx();
let kind = match mt { let kind = if tcx.sess.opts.optimize == OptLevel::No {
hir::Mutability::Not => { // Use conservative pointer kind if not optimizing. This saves us the
if ty.is_freeze(tcx.at(DUMMY_SP), cx.param_env()) { // Freeze/Unpin queries, and can save time in the codegen backend (noalias
PointerKind::Frozen // attributes in LLVM have compile-time cost even in unoptimized builds).
} else { PointerKind::Shared
PointerKind::Shared } else {
match mt {
hir::Mutability::Not => {
if ty.is_freeze(tcx.at(DUMMY_SP), cx.param_env()) {
PointerKind::Frozen
} else {
PointerKind::Shared
}
} }
} hir::Mutability::Mut => {
hir::Mutability::Mut => { // References to self-referential structures should not be considered
// References to self-referential structures should not be considered // noalias, as another pointer to the structure can be obtained, that
// noalias, as another pointer to the structure can be obtained, that // is not based-on the original reference. We consider all !Unpin
// is not based-on the original reference. We consider all !Unpin // types to be potentially self-referential here.
// types to be potentially self-referential here. if ty.is_unpin(tcx.at(DUMMY_SP), cx.param_env()) {
if ty.is_unpin(tcx.at(DUMMY_SP), cx.param_env()) { PointerKind::UniqueBorrowed
PointerKind::UniqueBorrowed } else {
} else { PointerKind::Shared
PointerKind::Shared }
} }
} }
}; };

2
src/test/codegen/function-arguments.rs
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@ -1,4 +1,4 @@
// compile-flags: -C no-prepopulate-passes // compile-flags: -O -C no-prepopulate-passes
// ignore-tidy-linelength // ignore-tidy-linelength
// min-system-llvm-version: 12.0 // min-system-llvm-version: 12.0

2
src/test/codegen/noalias-unpin.rs
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@ -1,4 +1,4 @@
// compile-flags: -Z mutable-noalias=yes // compile-flags: -O -Z mutable-noalias=yes
#![crate_type = "lib"] #![crate_type = "lib"]

2
src/test/codegen/packed.rs
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@ -1,5 +1,5 @@
// ignore-tidy-linelength // ignore-tidy-linelength
// compile-flags: -C no-prepopulate-passes // compile-flags: -O -C no-prepopulate-passes
#![crate_type = "lib"] #![crate_type = "lib"]