aleksandr.urakov created this revision.
aleksandr.urakov added reviewers: rnk, zturner, rsmith.
aleksandr.urakov added a project: clang.
Herald added subscribers: cfe-commits, jdoerfert.
This patch fixes several small problems with external layouts support in
`MicrosoftRecordLayoutBuilder`:
- aligns properly the size of a struct that ends with a bit field. It was
aligned on byte before, not on the size of the field, so the struct size was
smaller than it should be;
- adjusts the struct size when injecting a vbptr in the case when there were no
bases or fields allocated after the vbptr. Similarly, without the adjustment
the struct was smaller than it should be;
- the same fix as above for the vfptr.
All these fixes affect the non-virtual size of a struct, so they are tested
through non-virtual inheritance.
Repository:
rC Clang
https://reviews.llvm.org/D58544
Files:
lib/AST/RecordLayoutBuilder.cpp
test/CodeGenCXX/Inputs/override-bit-field-layout.layout
test/CodeGenCXX/Inputs/override-layout-virtual-base.layout
test/CodeGenCXX/override-bit-field-layout.cpp
test/CodeGenCXX/override-layout-virtual-base.cpp
Index: test/CodeGenCXX/override-layout-virtual-base.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/override-layout-virtual-base.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -w -triple=x86_64-pc-win32 -fms-compatibility -fdump-record-layouts-simple -foverride-record-layout=%S/Inputs/override-layout-virtual-base.layout %s | FileCheck %s
+
+struct S1 {
+ int a;
+};
+
+struct S2 : virtual S1 {
+ virtual void foo() {}
+};
+
+// CHECK: Type: struct S3
+// CHECK: FieldOffsets: [128]
+struct S3 : S2 {
+ char b;
+};
+
+void use_structs() {
+ S1 s1s[sizeof(S1)];
+ S2 s2s[sizeof(S2)];
+ S3 s3s[sizeof(S3)];
+}
Index: test/CodeGenCXX/override-bit-field-layout.cpp
===================================================================
--- test/CodeGenCXX/override-bit-field-layout.cpp
+++ test/CodeGenCXX/override-bit-field-layout.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -w -fdump-record-layouts-simple -foverride-record-layout=%S/Inputs/override-bit-field-layout.layout %s | FileCheck %s
+// RUN: %clang_cc1 -w -triple=x86_64-pc-win32 -fms-compatibility -fdump-record-layouts-simple -foverride-record-layout=%S/Inputs/override-bit-field-layout.layout %s | FileCheck %s
// CHECK: Type: struct S1
// CHECK: FieldOffsets: [0, 11]
@@ -14,7 +14,23 @@
short a : 3;
};
+// CHECK: Type: struct S3
+// CHECK: Size:32
+// CHECK: FieldOffsets: [0, 1]
+struct S3 {
+ int a : 1;
+ int b : 2;
+};
+
+// CHECK: Type: struct S4
+// CHECK: FieldOffsets: [32]
+struct S4 : S3 {
+ char c;
+};
+
void use_structs() {
S1 s1s[sizeof(S1)];
S2 s2s[sizeof(S2)];
+ S3 s3s[sizeof(S3)];
+ S4 s4s[sizeof(S4)];
}
Index: test/CodeGenCXX/Inputs/override-layout-virtual-base.layout
===================================================================
--- /dev/null
+++ test/CodeGenCXX/Inputs/override-layout-virtual-base.layout
@@ -0,0 +1,8 @@
+
+*** Dumping AST Record Layout
+Type: struct S2
+
+Layout: <ASTRecordLayout
+ Size:64
+ Alignment:64
+ FieldOffsets: []>
Index: test/CodeGenCXX/Inputs/override-bit-field-layout.layout
===================================================================
--- test/CodeGenCXX/Inputs/override-bit-field-layout.layout
+++ test/CodeGenCXX/Inputs/override-bit-field-layout.layout
@@ -14,3 +14,11 @@
Size:128
Alignment:64
FieldOffsets: [64]>
+
+*** Dumping AST Record Layout
+Type: struct S3
+
+Layout: <ASTRecordLayout
+ Size:32
+ Alignment:32
+ FieldOffsets: [0, 1]>
Index: lib/AST/RecordLayoutBuilder.cpp
===================================================================
--- lib/AST/RecordLayoutBuilder.cpp
+++ lib/AST/RecordLayoutBuilder.cpp
@@ -2692,7 +2692,8 @@
auto FieldBitOffset = External.getExternalFieldOffset(FD);
placeFieldAtBitOffset(FieldBitOffset);
auto NewSize = Context.toCharUnitsFromBits(
- llvm::alignTo(FieldBitOffset + Width, Context.getCharWidth()));
+ llvm::alignDown(FieldBitOffset, Context.toBits(Info.Alignment)) +
+ Context.toBits(Info.Size));
Size = std::max(Size, NewSize);
Alignment = std::max(Alignment, Info.Alignment);
} else if (IsUnion) {
@@ -2741,12 +2742,17 @@
CharUnits InjectionSite = VBPtrOffset;
// But before we do, make sure it's properly aligned.
VBPtrOffset = VBPtrOffset.alignTo(PointerInfo.Alignment);
+ // Determine where the first field should be laid out after the vbptr.
+ CharUnits FieldStart = VBPtrOffset + PointerInfo.Size;
// Shift everything after the vbptr down, unless we're using an external
// layout.
- if (UseExternalLayout)
+ if (UseExternalLayout) {
+ // It is possible that there were no fields or bases located after vbptr,
+ // so the size was not adjusted before.
+ if (Size < FieldStart)
+ Size = FieldStart;
return;
- // Determine where the first field should be laid out after the vbptr.
- 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)
@@ -2771,8 +2777,14 @@
if (HasVBPtr)
VBPtrOffset += Offset;
- if (UseExternalLayout)
+ if (UseExternalLayout) {
+ // The class may have no bases or fields, but still have a vfptr
+ // (e.g. it's an interface class). The size was not correctly set before
+ // in this case.
+ if (FieldOffsets.empty() && Bases.empty())
+ Size += Offset;
return;
+ }
Size += Offset;
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