From a72666ed56ec5f1b6d254c7020cf86143edc6dbd Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Tue, 20 Sep 2022 13:03:43 -0700 Subject: [PATCH] rustc_transmute: fix big-endian discriminants --- compiler/rustc_transmute/src/layout/tree.rs | 22 +++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/compiler/rustc_transmute/src/layout/tree.rs b/compiler/rustc_transmute/src/layout/tree.rs index 211c813b800..acd4fa63d78 100644 --- a/compiler/rustc_transmute/src/layout/tree.rs +++ b/compiler/rustc_transmute/src/layout/tree.rs @@ -404,7 +404,7 @@ pub(crate) mod rustc { .unwrap(); trace!(?discr_layout, "computed discriminant layout"); variant_layout = variant_layout.extend(discr_layout).unwrap().0; - tree = tree.then(Self::from_disr(discr, tcx, layout_summary.discriminant_size)); + tree = tree.then(Self::from_discr(discr, tcx, layout_summary.discriminant_size)); } // Next come fields. @@ -444,11 +444,21 @@ pub(crate) mod rustc { Ok(tree) } - pub fn from_disr(discr: Discr<'tcx>, tcx: TyCtxt<'tcx>, size: usize) -> Self { - // FIXME(@jswrenn): I'm certain this is missing needed endian nuance. - let bytes = discr.val.to_ne_bytes(); - let bytes = &bytes[..size]; - Self::Seq(bytes.into_iter().copied().map(|b| Self::from_bits(b)).collect()) + pub fn from_discr(discr: Discr<'tcx>, tcx: TyCtxt<'tcx>, size: usize) -> Self { + use rustc_target::abi::Endian; + + let bytes: [u8; 16]; + let bytes = match tcx.data_layout.endian { + Endian::Little => { + bytes = discr.val.to_le_bytes(); + &bytes[..size] + } + Endian::Big => { + bytes = discr.val.to_be_bytes(); + &bytes[bytes.len() - size..] + } + }; + Self::Seq(bytes.iter().map(|&b| Self::from_bits(b)).collect()) } }