MS ABI: vptr injection should obey alignment requirements

vptr injection must inject padding equivalent to the alignment of the
most aligned non-virtual subobject, not the alignment of the enclosing
record.

To fascilitate this change, don't let record layout observe the
alignment of the record until we've injected our vptrs. Also, do not
allow the alignment of vbases to affect required alignment until just
before we insert the vtordisp field.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201199 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp
index 903f973e616adf9a3b507b793d4d45694e03ec11..1f64b4be50762aeba0328f093b3a6207cf310eaa 100644 (file)
--- a/lib/AST/RecordLayoutBuilder.cpp
+++ b/lib/AST/RecordLayoutBuilder.cpp
@@ -2277,6 +2277,8 @@ void MicrosoftRecordLayoutBuilder::layout(const RecordDecl *RD) {
   initializeLayout(RD);
   layoutFields(RD);
   DataSize = Size = Size.RoundUpToAlignment(Alignment);
+  RequiredAlignment = std::max(
+      RequiredAlignment, Context.toCharUnitsFromBits(RD->getMaxAlignment()));
   finalizeLayout(RD);
 }
 
@@ -2287,6 +2289,8 @@ void MicrosoftRecordLayoutBuilder::cxxLayout(const CXXRecordDecl *RD) {
   layoutFields(RD);
   injectVPtrs(RD);
   DataSize = Size = Size.RoundUpToAlignment(Alignment);
+  RequiredAlignment = std::max(
+      RequiredAlignment, Context.toCharUnitsFromBits(RD->getMaxAlignment()));
   layoutVirtualBases(RD);
   finalizeLayout(RD);
 }
@@ -2300,8 +2304,6 @@ void MicrosoftRecordLayoutBuilder::initializeLayout(const RecordDecl *RD) {
   // In 32-bit mode we do not.  The check to see if we need to perform alignment
   // checks the RequiredAlignment field and performs alignment if it isn't 0.
   RequiredAlignment = Is64BitMode ? CharUnits::One() : CharUnits::Zero();
-  RequiredAlignment = std::max(RequiredAlignment,
-    Context.toCharUnitsFromBits(RD->getMaxAlignment()));
   // Compute the maximum field alignment.
   MaxFieldAlignment = CharUnits::Zero();
   // Honor the default struct packing maximum alignment flag.
@@ -2352,14 +2354,14 @@ MicrosoftRecordLayoutBuilder::layoutNonVirtualBases(const CXXRecordDecl *RD) {
        i != e; ++i) {
     const CXXRecordDecl *BaseDecl = i->getType()->getAsCXXRecordDecl();
     const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
-    // Track RequiredAlignment for all bases in this pass.
-    RequiredAlignment = std::max(RequiredAlignment,
-                                 BaseLayout.getRequiredAlignment());
     // Mark and skip virtual bases.
     if (i->isVirtual()) {
       HasVBPtr = true;
       continue;
     }
+    // Track RequiredAlignment for all bases in this pass.
+    RequiredAlignment = std::max(RequiredAlignment,
+                                 BaseLayout.getRequiredAlignment());
     // Check fo a base to share a VBPtr with.
     if (!SharedVBPtrBase && BaseLayout.hasVBPtr()) {
       SharedVBPtrBase = BaseDecl;
@@ -2525,7 +2527,8 @@ void MicrosoftRecordLayoutBuilder::injectVBPtr(const CXXRecordDecl *RD) {
   CharUnits FieldStart = VBPtrOffset + PointerInfo.Size;
   // Make sure that the amount we push the fields back by is a multiple of the
   // alignment.
-  CharUnits Offset = (FieldStart - InjectionSite).RoundUpToAlignment(Alignment);
+  CharUnits Offset = (FieldStart - InjectionSite).RoundUpToAlignment(
+      std::max(RequiredAlignment, Alignment));
   // Increase the size of the object and push back all fields by the offset
   // amount.
   Size += Offset;
@@ -2547,11 +2550,12 @@ void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) {
     return;
   // Make sure that the amount we push the struct back by is a multiple of the
   // alignment.
-  CharUnits Offset = PointerInfo.Size.RoundUpToAlignment(Alignment);
+  CharUnits Offset = PointerInfo.Size.RoundUpToAlignment(
+      std::max(RequiredAlignment, Alignment));
   // Increase the size of the object and push back all fields, the vbptr and all
   // bases by the offset amount.
   Size += Offset;
-  for (SmallVector<uint64_t, 16>::iterator i = FieldOffsets.begin(),
+  for (SmallVectorImpl<uint64_t>::iterator i = FieldOffsets.begin(),
                                            e = FieldOffsets.end();
        i != e; ++i)
     *i += Context.toBits(Offset);
@@ -2646,6 +2650,14 @@ void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
   // The alignment of the vtordisp is at least the required alignment of the
   // entire record.  This requirement may be present to support vtordisp
   // injection.
+  for (CXXRecordDecl::base_class_const_iterator i = RD->vbases_begin(),
+                                                e = RD->vbases_end();
+       i != e; ++i) {
+    const CXXRecordDecl *BaseDecl = i->getType()->getAsCXXRecordDecl();
+    const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
+    RequiredAlignment =
+        std::max(RequiredAlignment, BaseLayout.getRequiredAlignment());
+  }
   VtorDispAlignment = std::max(VtorDispAlignment, RequiredAlignment);
   // Compute the vtordisp set.
   llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtordispSet =

diff --git a/test/Layout/ms-x86-pack-and-align.cpp b/test/Layout/ms-x86-pack-and-align.cpp
index c09c36399468abf550c6761a6b72ee609eb9062e..a9685f12e7c85208f197b1cea05d1953a8801df1 100644 (file)
--- a/test/Layout/ms-x86-pack-and-align.cpp
+++ b/test/Layout/ms-x86-pack-and-align.cpp
@@ -371,6 +371,49 @@ struct KB : KA { __declspec(align(2)) char a; };
 // CHECK-X64-NEXT:      | [sizeof=4, align=2
 // CHECK-X64-NEXT:      |  nvsize=3, nvalign=2]
 
+#pragma pack(1)
+struct L {
+  virtual void fun() {}
+  __declspec(align(256)) int Field;
+};
+
+// CHECK: *** Dumping AST Record Layout
+// CHECK-NEXT:    0 | struct L
+// CHECK-NEXT:    0 |   (L vftable pointer)
+// CHECK-NEXT:  256 |   int Field
+// CHECK-NEXT:      | [sizeof=512, align=256
+// CHECK-NEXT:      |  nvsize=260, nvalign=256]
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64-NEXT:    0 | struct L
+// CHECK-X64-NEXT:    0 |   (L vftable pointer)
+// CHECK-X64-NEXT:  256 |   int Field
+// CHECK-X64-NEXT:      | [sizeof=512, align=256
+// CHECK-X64-NEXT:      |  nvsize=260, nvalign=256]
+
+#pragma pack()
+struct MA {};
+#pragma pack(1)
+struct MB : virtual MA {
+  __declspec(align(256)) int Field;
+};
+
+// CHECK: *** Dumping AST Record Layout
+// CHECK: *** Dumping AST Record Layout
+// CHECK-NEXT:    0 | struct MB
+// CHECK-NEXT:    0 |   (MB vbtable pointer)
+// CHECK-NEXT:  256 |   int Field
+// CHECK-NEXT:  260 |   struct MA (virtual base) (empty)
+// CHECK-NEXT:      | [sizeof=512, align=256
+// CHECK-NEXT:      |  nvsize=260, nvalign=256]
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64-NEXT:    0 | struct MB
+// CHECK-X64-NEXT:    0 |   (MB vbtable pointer)
+// CHECK-X64-NEXT:  256 |   int Field
+// CHECK-X64-NEXT:  260 |   struct MA (virtual base) (empty)
+// CHECK-X64-NEXT:      | [sizeof=512, align=256
+// CHECK-X64-NEXT:      |  nvsize=260, nvalign=256]
+
 int a[
 sizeof(X)+
 sizeof(Y)+
@@ -387,4 +430,6 @@ sizeof(YF)+
 sizeof(D2)+
 sizeof(JC)+
 sizeof(KB)+
+sizeof(L)+
+sizeof(MB)+
 0];