[gcc r10-9898] d: Respect explicit align(N) type alignment (PR100935)

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

https://gcc.gnu.org/g:f7ece1a32000a9943f5bd5ac597d6ce3829aff8e

commit r10-9898-gf7ece1a32000a9943f5bd5ac597d6ce3829aff8e
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 | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/gcc/d/dmd/mtype.c b/gcc/d/dmd/mtype.c
index c11772a7740..0ec577d0c1e 100644
--- a/gcc/d/dmd/mtype.c
+++ b/gcc/d/dmd/mtype.c
@@ -2060,7 +2060,10 @@ 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 bf602ff31a4..0c727e2fec5 100644
--- a/gcc/testsuite/gdc.test/compilable/aggr_alignment.d
+++ b/gcc/testsuite/gdc.test/compilable/aggr_alignment.d
@@ -27,6 +27,26 @@ 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);
 
 /***************************************************/
 // https://issues.dlang.org/show_bug.cgi?id=19914