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Auto merge of #36321 - uweigand:enum-abi, r=eddyb

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Follow target ABI sign-/zero-extension rules for enum types

While attempting to port Rust to s390x, I ran into an ABI violation
(that caused rust_eh_personality to be miscompiled, breaking unwinding).
The problem is that this function returns an enum type, which is
supposed to be sign-extended according to the s390x ABI.  However,
common code would ignore target sign-/zero-extension rules for any
types that do not satisfy is_integral(), which includes enums.

For the general case of Rust enum types, which map to structure types
with a discriminant, that seems correct.  However, in the special case
of simple enums that map directly to C enum types (i.e. LLVM integers),
this is incorrect; we must follow the target extension rules for those.

Signed-off-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
This commit is contained in:
bors 2016-09-08 19:15:50 -07:00 • committed by GitHub
commit 1df64450ec
1 changed files with 6 additions and 0 deletions
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6
src/librustc_trans/abi.rs
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@ -35,6 +35,7 @@ use std::cmp;
pub use syntax::abi::Abi;
pub use rustc::ty::layout::{FAT_PTR_ADDR, FAT_PTR_EXTRA};
use rustc::ty::layout::Layout;
#[derive(Clone, Copy, PartialEq, Debug)]
enum ArgKind {
@ -317,6 +318,11 @@ impl FnType {
if ty.is_integral() {
arg.signedness = Some(ty.is_signed());
}
// Rust enum types that map onto C enums also need to follow
// the target ABI zero-/sign-extension rules.
if let Layout::CEnum { signed, .. } = *ccx.layout_of(ty) {
arg.signedness = Some(signed);
}
if llsize_of_real(ccx, arg.ty) == 0 {
// For some forsaken reason, x86_64-pc-windows-gnu
// doesn't ignore zero-sized struct arguments.