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rustc_trans: do not store pair fields if they are ZSTs.

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This commit is contained in:
Eduard-Mihai Burtescu 2017-06-06 21:13:13 +03:00
parent c94a9ac8ae
commit 1a2eb4953e
2 changed files with 20 additions and 6 deletions
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16
src/librustc_trans/mir/operand.rs
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@ -338,8 +338,20 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
let a = base::from_immediate(bcx, a);
let b = base::from_immediate(bcx, b);
bcx.store(a, bcx.struct_gep(lldest, ix0), f_align);
bcx.store(b, bcx.struct_gep(lldest, ix1), f_align);
// See comment above about zero-sized values.
let (a_zst, b_zst) = common::type_pair_fields(bcx.ccx, operand.ty)
.map_or((false, false), |[a_ty, b_ty]| {
(common::type_is_zero_size(bcx.ccx, a_ty),
common::type_is_zero_size(bcx.ccx, b_ty))
});
if !a_zst {
bcx.store(a, bcx.struct_gep(lldest, ix0), f_align);
}
if !b_zst {
bcx.store(b, bcx.struct_gep(lldest, ix1), f_align);
}
}
}
}

10
src/test/codegen/mir_zst_stores.rs
View File

@ -13,13 +13,15 @@
#![crate_type = "lib"]
use std::marker::PhantomData;
#[derive(Copy, Clone)]
struct Zst { phantom: PhantomData<Zst> }
// CHECK-LABEL: @mir
// CHECK-NOT: store{{.*}}undef
#[no_mangle]
fn mir(){
// CHECK-NOT: getelementptr
// CHECK-NOT: store{{.*}}undef
fn mir() {
let x = Zst { phantom: PhantomData };
let y = (x, 0);
drop(y);
drop((0, x));
}