Auto merge of #38523 - camlorn:disable_field_reordering, r=nikomatsakis

Disable field reordering

This was decided via IRC and needs a backport to beta.  Basically, #37429 broke servo, and probably needs an announcement and opt-in flag.  I didn't run all tests locally but think I've already reverted all the ones that need to be reverted.

r? @nikomatsakis

5 files changed, 36 insertions, 36 deletions

diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index 53ed103ad91..ebac30c8e50 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -575,6 +575,10 @@ impl<'a, 'gcx, 'tcx> Struct {
             });
         }
 
+        // Disable field reordering until we can decide what to do.
+        // The odd pattern here avoids a warning about the value never being read.
+        if can_optimize { can_optimize = false }
+
         let (optimize, sort_ascending) = match kind {
             StructKind::AlwaysSizedUnivariant => (can_optimize, false),
             StructKind::MaybeUnsizedUnivariant => (can_optimize, false),
diff --git a/src/test/run-pass/type-sizes.rs b/src/test/run-pass/type-sizes.rs
index 6614a76107f..bbb01eaaf46 100644
--- a/src/test/run-pass/type-sizes.rs
+++ b/src/test/run-pass/type-sizes.rs
@@ -31,10 +31,6 @@ enum e3 {
     a([u16; 0], u8), b
 }
 
-// Test struct field reordering to make sure it actually reorders.
-struct WillOptimize1(u8, u16, u8);
-struct WillOptimize2 { a: u8, b: u16, c: u8}
-
 pub fn main() {
     assert_eq!(size_of::<u8>(), 1 as usize);
     assert_eq!(size_of::<u32>(), 4 as usize);
@@ -58,7 +54,4 @@ pub fn main() {
     assert_eq!(size_of::<e1>(), 8 as usize);
     assert_eq!(size_of::<e2>(), 8 as usize);
     assert_eq!(size_of::<e3>(), 4 as usize);
-
-    assert_eq!(size_of::<WillOptimize1>(), 4);
-    assert_eq!(size_of::<WillOptimize2>(), 4);
 }
diff --git a/src/test/ui/print_type_sizes/nullable.stdout b/src/test/ui/print_type_sizes/nullable.stdout
index 830678f174f..dd999c4a5e4 100644
--- a/src/test/ui/print_type_sizes/nullable.stdout
+++ b/src/test/ui/print_type_sizes/nullable.stdout
@@ -1,22 +1,25 @@
-print-type-size type: `IndirectNonZero<u32>`: 12 bytes, alignment: 4 bytes
-print-type-size     field `.nested`: 8 bytes
-print-type-size     field `.post`: 2 bytes
+print-type-size type: `IndirectNonZero<u32>`: 20 bytes, alignment: 4 bytes
 print-type-size     field `.pre`: 1 bytes
-print-type-size     end padding: 1 bytes
-print-type-size type: `MyOption<IndirectNonZero<u32>>`: 12 bytes, alignment: 4 bytes
-print-type-size     variant `Some`: 12 bytes
-print-type-size         field `.0`: 12 bytes
-print-type-size type: `EmbeddedDiscr`: 8 bytes, alignment: 4 bytes
-print-type-size     variant `Record`: 7 bytes
-print-type-size         field `.val`: 4 bytes
-print-type-size         field `.post`: 2 bytes
-print-type-size         field `.pre`: 1 bytes
-print-type-size     end padding: 1 bytes
-print-type-size type: `NestedNonZero<u32>`: 8 bytes, alignment: 4 bytes
-print-type-size     field `.val`: 4 bytes
+print-type-size     padding: 3 bytes
+print-type-size     field `.nested`: 12 bytes, alignment: 4 bytes
 print-type-size     field `.post`: 2 bytes
+print-type-size     end padding: 2 bytes
+print-type-size type: `MyOption<IndirectNonZero<u32>>`: 20 bytes, alignment: 4 bytes
+print-type-size     variant `Some`: 20 bytes
+print-type-size         field `.0`: 20 bytes
+print-type-size type: `EmbeddedDiscr`: 12 bytes, alignment: 4 bytes
+print-type-size     variant `Record`: 10 bytes
+print-type-size         field `.pre`: 1 bytes
+print-type-size         padding: 3 bytes
+print-type-size         field `.val`: 4 bytes, alignment: 4 bytes
+print-type-size         field `.post`: 2 bytes
+print-type-size     end padding: 2 bytes
+print-type-size type: `NestedNonZero<u32>`: 12 bytes, alignment: 4 bytes
 print-type-size     field `.pre`: 1 bytes
-print-type-size     end padding: 1 bytes
+print-type-size     padding: 3 bytes
+print-type-size     field `.val`: 4 bytes, alignment: 4 bytes
+print-type-size     field `.post`: 2 bytes
+print-type-size     end padding: 2 bytes
 print-type-size type: `MyOption<core::nonzero::NonZero<u32>>`: 4 bytes, alignment: 4 bytes
 print-type-size     variant `Some`: 4 bytes
 print-type-size         field `.0`: 4 bytes
diff --git a/src/test/ui/print_type_sizes/packed.stdout b/src/test/ui/print_type_sizes/packed.stdout
index 83fd333c9c7..1278a7d7c92 100644
--- a/src/test/ui/print_type_sizes/packed.stdout
+++ b/src/test/ui/print_type_sizes/packed.stdout
@@ -1,11 +1,13 @@
-print-type-size type: `Padded`: 12 bytes, alignment: 4 bytes
-print-type-size     field `.g`: 4 bytes
-print-type-size     field `.h`: 2 bytes
+print-type-size type: `Padded`: 16 bytes, alignment: 4 bytes
 print-type-size     field `.a`: 1 bytes
 print-type-size     field `.b`: 1 bytes
+print-type-size     padding: 2 bytes
+print-type-size     field `.g`: 4 bytes, alignment: 4 bytes
 print-type-size     field `.c`: 1 bytes
+print-type-size     padding: 1 bytes
+print-type-size     field `.h`: 2 bytes, alignment: 2 bytes
 print-type-size     field `.d`: 1 bytes
-print-type-size     end padding: 2 bytes
+print-type-size     end padding: 3 bytes
 print-type-size type: `Packed`: 10 bytes, alignment: 1 bytes
 print-type-size     field `.a`: 1 bytes
 print-type-size     field `.b`: 1 bytes
diff --git a/src/test/ui/print_type_sizes/padding.stdout b/src/test/ui/print_type_sizes/padding.stdout
index 0eaff7118b3..bb95f790bd9 100644
--- a/src/test/ui/print_type_sizes/padding.stdout
+++ b/src/test/ui/print_type_sizes/padding.stdout
@@ -1,12 +1,10 @@
 print-type-size type: `E1`: 12 bytes, alignment: 4 bytes
-print-type-size     discriminant: 1 bytes
-print-type-size     variant `A`: 7 bytes
+print-type-size     discriminant: 4 bytes
+print-type-size     variant `A`: 5 bytes
+print-type-size         field `.0`: 4 bytes
 print-type-size         field `.1`: 1 bytes
-print-type-size         padding: 2 bytes
-print-type-size         field `.0`: 4 bytes, alignment: 4 bytes
-print-type-size     variant `B`: 11 bytes
-print-type-size         padding: 3 bytes
-print-type-size         field `.0`: 8 bytes, alignment: 4 bytes
+print-type-size     variant `B`: 8 bytes
+print-type-size         field `.0`: 8 bytes
 print-type-size type: `E2`: 12 bytes, alignment: 4 bytes
 print-type-size     discriminant: 1 bytes
 print-type-size     variant `A`: 7 bytes
@@ -17,7 +15,7 @@ print-type-size     variant `B`: 11 bytes
 print-type-size         padding: 3 bytes
 print-type-size         field `.0`: 8 bytes, alignment: 4 bytes
 print-type-size type: `S`: 8 bytes, alignment: 4 bytes
-print-type-size     field `.g`: 4 bytes
 print-type-size     field `.a`: 1 bytes
 print-type-size     field `.b`: 1 bytes
-print-type-size     end padding: 2 bytes
+print-type-size     padding: 2 bytes
+print-type-size     field `.g`: 4 bytes, alignment: 4 bytes