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From 2946828fcb8e2e68a16839dfcf4319bf119f8acd Mon Sep 17 00:00:00 2001
From: Josh Stone <jistone@redhat.com>
Date: Tue, 20 Sep 2022 13:03:43 -0700
Subject: [PATCH] rustc_transmute: fix big-endian discriminants
(cherry picked from commit a72666ed56ec5f1b6d254c7020cf86143edc6dbd)
---
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 70b3ba02b05b..e4fcde35ed37 100644
--- a/compiler/rustc_transmute/src/layout/tree.rs
+++ b/compiler/rustc_transmute/src/layout/tree.rs
@@ -402,7 +402,7 @@ fn from_repr_c_variant(
.unwrap();
tracing::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.
@@ -442,11 +442,21 @@ fn from_repr_c_variant(
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())
}
}
--
2.37.3