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Add -Zmutable-noalias flag #45012

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Merged
merged 2 commits into from
Oct 8, 2017
Merged

Add -Zmutable-noalias flag #45012

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3647129
Add -Zmutable-noalias flag
Gankra Oct 3, 2017
a6dea41
Make -Cpanic=abort imply -Zmutable-noalias
Gankra Oct 4, 2017
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2 changes: 2 additions & 0 deletions src/librustc/session/config.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1060,6 +1060,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
"print the result of the translation item collection pass"),
mir_opt_level: usize = (1, parse_uint, [TRACKED],
"set the MIR optimization level (0-3, default: 1)"),
mutable_noalias: bool = (false, parse_bool, [UNTRACKED],
"emit noalias metadata for mutable references"),
dump_mir: Option<String> = (None, parse_opt_string, [UNTRACKED],
"dump MIR state at various points in translation"),
dump_mir_dir: Option<String> = (None, parse_opt_string, [UNTRACKED],
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13 changes: 12 additions & 1 deletion src/librustc_trans/abi.rs
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Expand Up @@ -37,6 +37,7 @@ use type_of;
use rustc::hir;
use rustc::ty::{self, Ty};
use rustc::ty::layout::{self, Layout, LayoutTyper, TyLayout, Size};
use rustc_back::PanicStrategy;

use libc::c_uint;
use std::cmp;
Expand Down Expand Up @@ -760,7 +761,17 @@ impl<'a, 'tcx> FnType<'tcx> {
// on memory dependencies rather than pointer equality
let is_freeze = ccx.shared().type_is_freeze(mt.ty);

if mt.mutbl != hir::MutMutable && is_freeze {
let no_alias_is_safe =
if ccx.shared().tcx().sess.opts.debugging_opts.mutable_noalias ||
ccx.shared().tcx().sess.panic_strategy() == PanicStrategy::Abort {
// Mutable refrences or immutable shared references
mt.mutbl == hir::MutMutable || is_freeze
} else {
// Only immutable shared references
mt.mutbl != hir::MutMutable && is_freeze
};

if no_alias_is_safe {
arg.attrs.set(ArgAttribute::NoAlias);
}

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