[gcc r9-9575] d: Respect explicit align(N) type alignment (PR100935)

[Iain Buclaw <ibuclaw@gcc.gnu.org>]

https://gcc.gnu.org/g:fe555102dc224b4d946becc8a9db514ecec66161

commit r9-9575-gfe555102dc224b4d946becc8a9db514ecec66161
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Wed Jun 9 19:37:22 2021 +0200

    d: Respect explicit align(N) type alignment (PR100935)
    
    It was previously the natural type alignment, defined as the maximum of
    the field alignments for an aggregate.  Make sure an explicit align(N)
    overrides it.
    
    gcc/d/ChangeLog:
    
            PR d/100935
            * dmd/mtype.c (Type::getProperty): Prefer explicit alignment over
            natural alignment for alignof property.
    
    gcc/testsuite/ChangeLog:
    
            PR d/100935
            * gdc.test/compilable/aggr_alignment.d: Add test cases.
    
    (cherry picked from commit 3ba036dd1a752d29764ad44adca6e68bec9599fe)

Diff:
---
 gcc/d/dmd/mtype.c                                  |  5 ++++-
 gcc/testsuite/gdc.test/compilable/aggr_alignment.d | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/gcc/d/dmd/mtype.c b/gcc/d/dmd/mtype.c
index d0e73967d45..585199033af 100644
--- a/gcc/d/dmd/mtype.c
+++ b/gcc/d/dmd/mtype.c
@@ -2059,7 +2059,10 @@ Expression *Type::getProperty(Loc loc, Identifier *ident, int flag)
     }
     else if (ident == Id::__xalignof)
     {
-        e = new IntegerExp(loc, alignsize(), Type::tsize_t);
+        unsigned explicitAlignment = alignment();
+        unsigned naturalAlignment = alignsize();
+        unsigned actualAlignment = (explicitAlignment == STRUCTALIGN_DEFAULT ? naturalAlignment : explicitAlignment);
+        e = new IntegerExp(loc, actualAlignment, Type::tsize_t);
     }
     else if (ident == Id::_init)
     {
diff --git a/gcc/testsuite/gdc.test/compilable/aggr_alignment.d b/gcc/testsuite/gdc.test/compilable/aggr_alignment.d
index 3a80a039e26..5b3542828dd 100644
--- a/gcc/testsuite/gdc.test/compilable/aggr_alignment.d
+++ b/gcc/testsuite/gdc.test/compilable/aggr_alignment.d
@@ -26,3 +26,24 @@ enum payloadOffset = C2.bytes.offsetof;
 static assert(C2.int1.offsetof == payloadOffset + 8);
 static assert(C2.alignof == size_t.sizeof);
 static assert(__traits(classInstanceSize, C2) == payloadOffset + 12);
+
+align(8) struct PaddedStruct
+{
+    bool flag;
+    align(2) S1 s1;
+}
+
+static assert(PaddedStruct.s1.offsetof == 2);
+static assert(PaddedStruct.alignof == 8);
+static assert(PaddedStruct.sizeof == 16);
+
+align(1) struct UglyStruct
+{
+    bool flag;
+    int i;
+    ubyte u;
+}
+
+static assert(UglyStruct.i.offsetof == 4);
+static assert(UglyStruct.alignof == 1);
+static assert(UglyStruct.sizeof == 9);