efriedma updated this revision to Diff 267999.
efriedma added a comment.
This should work correctly, now, I think?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D79052/new/
https://reviews.llvm.org/D79052
Files:
clang/lib/CodeGen/CodeGenModule.cpp
clang/test/CodeGenCXX/alignment.cpp
Index: clang/test/CodeGenCXX/alignment.cpp
===================================================================
--- clang/test/CodeGenCXX/alignment.cpp
+++ clang/test/CodeGenCXX/alignment.cpp
@@ -308,4 +308,20 @@
D d;
AlignedArray result = d.bArray;
}
+
+ // CHECK-LABEL: @_ZN5test11hEPA_NS_1BE
+ void h(B (*b)[]) {
+ // CHECK: [[RESULT:%.*]] = alloca [[ARRAY]], align 64
+ // CHECK: [[B_P:%.*]] = load [0 x [[B]]]*, [0 x [[B]]]**
+ // CHECK: [[ELEMENT_P:%.*]] = getelementptr inbounds [0 x [[B]]], [0 x [[B]]]* [[B_P]], i64 0
+ // CHECK: [[ARRAY_P:%.*]] = getelementptr inbounds [[B]], [[B]]* [[ELEMENT_P]], i32 0, i32 2
+ // CHECK: [[T0:%.*]] = bitcast [[ARRAY]]* [[RESULT]] to i8*
+ // CHECK: [[T1:%.*]] = bitcast [[ARRAY]]* [[ARRAY_P]] to i8*
+ // CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 64 [[T0]], i8* align 16 [[T1]], i64 16, i1 false)
+ AlignedArray result = (*b)->bArray;
+ }
}
+
+// CHECK-LABEL: @_Z22incomplete_array_derefPA_i
+// CHECK: load i32, i32* {{%.*}}, align 4
+int incomplete_array_deref(int (*p)[]) { return (*p)[2]; }
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -5982,6 +5982,9 @@
if (TBAAInfo)
*TBAAInfo = getTBAAAccessInfo(T);
+ // FIXME: This duplicates logic in ASTContext::getTypeAlignIfKnown. But
+ // that doesn't return the information we need to compute BaseInfo.
+
// Honor alignment typedef attributes even on incomplete types.
// We also honor them straight for C++ class types, even as pointees;
// there's an expressivity gap here.
@@ -5993,32 +5996,46 @@
}
}
+ bool AlignForArray = T->isArrayType();
+
+ // Analyze the base element type, so we don't get confused by incomplete
+ // array types.
+ T = getContext().getBaseElementType(T);
+
+ if (T->isIncompleteType()) {
+ // We could try to replicate the logic from
+ // ASTContext::getTypeAlignIfKnown, but nothing uses the alignment if the
+ // type is incomplete, so it's impossible to test. We could try to reuse
+ // getTypeAlignIfKnown, but that doesn't return the information we need
+ // to set BaseInfo. So just ignore the possibility that the alignment is
+ // greater than one.
+ if (BaseInfo)
+ *BaseInfo = LValueBaseInfo(AlignmentSource::Type);
+ return CharUnits::One();
+ }
+
if (BaseInfo)
*BaseInfo = LValueBaseInfo(AlignmentSource::Type);
CharUnits Alignment;
- if (T->isIncompleteType()) {
- Alignment = CharUnits::One(); // Shouldn't be used, but pessimistic is best.
+ // For C++ class pointees, we don't know whether we're pointing at a
+ // base or a complete object, so we generally need to use the
+ // non-virtual alignment.
+ const CXXRecordDecl *RD;
+ if (forPointeeType && !AlignForArray && (RD = T->getAsCXXRecordDecl())) {
+ Alignment = getClassPointerAlignment(RD);
} else {
- // For C++ class pointees, we don't know whether we're pointing at a
- // base or a complete object, so we generally need to use the
- // non-virtual alignment.
- const CXXRecordDecl *RD;
- if (forPointeeType && (RD = T->getAsCXXRecordDecl())) {
- Alignment = getClassPointerAlignment(RD);
- } else {
- Alignment = getContext().getTypeAlignInChars(T);
- if (T.getQualifiers().hasUnaligned())
- Alignment = CharUnits::One();
- }
+ Alignment = getContext().getTypeAlignInChars(T);
+ if (T.getQualifiers().hasUnaligned())
+ Alignment = CharUnits::One();
+ }
- // Cap to the global maximum type alignment unless the alignment
- // was somehow explicit on the type.
- if (unsigned MaxAlign = getLangOpts().MaxTypeAlign) {
- if (Alignment.getQuantity() > MaxAlign &&
- !getContext().isAlignmentRequired(T))
- Alignment = CharUnits::fromQuantity(MaxAlign);
- }
+ // Cap to the global maximum type alignment unless the alignment
+ // was somehow explicit on the type.
+ if (unsigned MaxAlign = getLangOpts().MaxTypeAlign) {
+ if (Alignment.getQuantity() > MaxAlign &&
+ !getContext().isAlignmentRequired(T))
+ Alignment = CharUnits::fromQuantity(MaxAlign);
}
return Alignment;
}
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