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authorDouglas Gregor <dgregor@apple.com>2012-01-26 07:55:45 +0000
committerDouglas Gregor <dgregor@apple.com>2012-01-26 07:55:45 +0000
commit453dbcbe30093fbf947a0bec2fbd46e9694eafe9 (patch)
treed7bdab4d63fe4983cf3a51b38621e9f37b696847 /include/clang/Frontend/LayoutOverrideSource.h
parent5b78a244ef213835337a5a860fe7c3f2fa90a943 (diff)
Extend the ExternalASTSource interface to allow the AST source to
provide the layout of records, rather than letting Clang compute the layout itself. LLDB provides the motivation for this feature: because various layout-altering attributes (packed, aligned, etc.) don't get reliably get placed into DWARF, the record layouts computed by LLDB from the reconstructed records differ from the actual layouts, and badness occurs. This interface lets the DWARF data drive layout, so we don't need the attributes preserved to get the answer write. The testing methodology for this change is fun. I've introduced a variant of -fdump-record-layouts called -fdump-record-layouts-simple that always has the simple C format and provides size/alignment/field offsets. There is also a -cc1 option -foverride-record-layout=<file> to take the output of -fdump-record-layouts-simple and parse it to produce a set of overridden layouts, which is introduced into the AST via a testing-only ExternalASTSource (called LayoutOverrideSource). Each test contains a number of records to lay out, which use various layout-changing attributes, and then dumps the layouts. We then run the test again, using the preprocessor to eliminate the layout-changing attributes entirely (which would give us different layouts for the records), but supplying the previously-computed record layouts. Finally, we diff the layouts produced from the two runs to be sure that they are identical. Note that this code makes the assumption that we don't *have* to provide the offsets of bases or virtual bases to get the layout right, because the alignment attributes don't affect it. I believe this assumption holds, but if it does not, we can extend LayoutOverrideSource to also provide base offset information. Fixes the Clang side of <rdar://problem/10169539>. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149055 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'include/clang/Frontend/LayoutOverrideSource.h')
-rw-r--r--include/clang/Frontend/LayoutOverrideSource.h61
1 files changed, 61 insertions, 0 deletions
diff --git a/include/clang/Frontend/LayoutOverrideSource.h b/include/clang/Frontend/LayoutOverrideSource.h
new file mode 100644
index 0000000000..225efe690b
--- /dev/null
+++ b/include/clang/Frontend/LayoutOverrideSource.h
@@ -0,0 +1,61 @@
+//===--- LayoutOverrideSource.h --Override Record Layouts -----------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_FRONTEND_LAYOUTOVERRIDESOURCE_H
+#define LLVM_CLANG_FRONTEND_LAYOUTOVERRIDESOURCE_H
+
+#include "clang/AST/ExternalASTSource.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+
+namespace clang {
+ /// \brief An external AST source that overrides the layout of
+ /// a specified set of record types.
+ ///
+ /// This class is used only for testing the ability of external AST sources
+ /// to override the layout of record types. Its input is the output format
+ /// of the command-line argument -fdump-record-layouts.
+ class LayoutOverrideSource : public ExternalASTSource {
+ /// \brief The layout of a given record.
+ struct Layout {
+ /// \brief The size of the record.
+ uint64_t Size;
+
+ /// \brief The alignment of the record.
+ uint64_t Align;
+
+ /// \brief The offsets of the fields, in source order.
+ llvm::SmallVector<uint64_t, 8> FieldOffsets;
+ };
+
+ /// \brief The set of layouts that will be overridden.
+ llvm::StringMap<Layout> Layouts;
+
+ public:
+ /// \brief Create a new AST source that overrides the layout of some
+ /// set of record types.
+ ///
+ /// The file is the result of passing -fdump-record-layouts to a file.
+ explicit LayoutOverrideSource(llvm::StringRef Filename);
+
+ /// \brief If this particular record type has an overridden layout,
+ /// return that layout.
+ virtual bool
+ layoutRecordType(const RecordDecl *Record,
+ uint64_t &Size, uint64_t &Alignment,
+ llvm::DenseMap<const FieldDecl *, uint64_t> &FieldOffsets,
+ llvm::DenseMap<const CXXRecordDecl *, CharUnits> &BaseOffsets,
+ llvm::DenseMap<const CXXRecordDecl *, CharUnits> &VirtualBaseOffsets);
+
+ /// \brief Dump the overridden layouts.
+ void dump();
+ };
+}
+
+#endif