[PATCH] D107394: [AIX] "aligned" attribute does not decrease alignment

[Steven Wan via Phabricator via cfe-commits]

stevewan updated this revision to Diff 366051.
stevewan added a comment.

Rebase to latest main


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D107394/new/

https://reviews.llvm.org/D107394

Files:
  clang/lib/AST/RecordLayoutBuilder.cpp
  clang/test/Layout/aix-alignof-align-and-pack-attr.cpp


Index: clang/test/Layout/aix-alignof-align-and-pack-attr.cpp
===================================================================
--- clang/test/Layout/aix-alignof-align-and-pack-attr.cpp
+++ clang/test/Layout/aix-alignof-align-and-pack-attr.cpp
@@ -27,3 +27,23 @@
 
 // CHECK: @{{.*}}test3{{.*}}c{{.*}} = global %"struct.test3::C" zeroinitializer, align 16
 } // namespace test3
+
+namespace test4 {
+struct C {
+  struct CC {
+    long double ld;
+  } __attribute__((aligned(2))) cc;
+} c;
+
+// CHECK: @{{.*}}test4{{.*}}c{{.*}} = global %"struct.test4::C" zeroinitializer, align 8
+} // namespace test4
+
+namespace test5 {
+struct C {
+  struct CC {
+    long double ld;
+  } __attribute__((aligned(2), packed)) cc;
+} c;
+
+// CHECK: @{{.*}}test5{{.*}}c{{.*}} = global %"struct.test5::C" zeroinitializer, align 2
+} // namespace test5
Index: clang/lib/AST/RecordLayoutBuilder.cpp
===================================================================
--- clang/lib/AST/RecordLayoutBuilder.cpp
+++ clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1968,6 +1968,12 @@
     }
   }
 
+  const Type *Ty = D->getType()->getBaseElementTypeUnsafe();
+  // When used as part of a typedef, the 'aligned' attribute can be used to
+  // decrease alignment.
+  bool AlignAttrCanDecreaseAlignment =
+      AlignIsRequired && Ty->getAs<TypedefType>() != nullptr;
+
   // The AIX `power` alignment rules apply the natural alignment of the
   // "first member" if it is of a floating-point data type (or is an aggregate
   // whose recursively "first" member or element is such a type). The alignment
@@ -1978,7 +1984,7 @@
   // and zero-width bit-fields count as prior members; members of empty class
   // types marked `no_unique_address` are not considered to be prior members.
   CharUnits PreferredAlign = FieldAlign;
-  if (DefaultsToAIXPowerAlignment && !AlignIsRequired &&
+  if (DefaultsToAIXPowerAlignment && !AlignAttrCanDecreaseAlignment &&
       (FoundFirstNonOverlappingEmptyFieldForAIX || IsNaturalAlign)) {
     auto performBuiltinTypeAlignmentUpgrade = [&](const BuiltinType *BTy) {
       if (BTy->getKind() == BuiltinType::Double ||
@@ -1989,7 +1995,6 @@
       }
     };
 
-    const Type *Ty = D->getType()->getBaseElementTypeUnsafe();
     if (const ComplexType *CTy = Ty->getAs<ComplexType>()) {
       performBuiltinTypeAlignmentUpgrade(CTy->getElementType()->castAs<BuiltinType>());
     } else if (const BuiltinType *BTy = Ty->getAs<BuiltinType>()) {


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