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Debug Info: Represent local anonymous unions as anonymous unions 

and as artificial local variables in the debug info.

This is a follow-up to r236059. We can't get rid of the local variables
entirely because the gdb buildbot depends on them, but we can mark them
as artificial while still emitting the correct debug info. As I learned
from review comments other compilers also follow this model.

A paired commit in LLVM temporarily relaxes the debug info verifier to
not check the integrity of DW_OP_bit_pieces of artificial variables.

rdar://problem/20730771

llvm-svn: 236125
This commit is contained in:
Adrian Prantl 2015-04-29 16:52:31 +00:00
parent ba6ec4b70b
commit 00820abf02
2 changed files with 27 additions and 2 deletions
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11
clang/lib/CodeGen/CGDebugInfo.cpp
View File

@ -2839,6 +2839,13 @@ void CGDebugInfo::EmitDeclare(const VarDecl *VD, llvm::dwarf::Tag Tag,
// all union fields.
const RecordDecl *RD = cast<RecordDecl>(RT->getDecl());
if (RD->isUnion() && RD->isAnonymousStructOrUnion()) {
// GDB has trouble finding local variables in anonymous unions, so we emit
// artifical local variables for each of the members.
//
// FIXME: Remove this code as soon as GDB supports this.
// The debug info verifier in LLVM operates based on the assumption that a
// variable has the same size as its storage and we had to disable the check
// for artificial variables.
for (const auto *Field : RD->fields()) {
llvm::DIType *FieldTy = getOrCreateType(Field->getType(), Unit);
StringRef FieldName = Field->getName();
@ -2850,14 +2857,14 @@ void CGDebugInfo::EmitDeclare(const VarDecl *VD, llvm::dwarf::Tag Tag,
// Use VarDecl's Tag, Scope and Line number.
auto *D = DBuilder.createLocalVariable(
Tag, Scope, FieldName, Unit, Line, FieldTy,
CGM.getLangOpts().Optimize, Flags, ArgNo);
CGM.getLangOpts().Optimize, Flags | llvm::DINode::FlagArtificial,
ArgNo);
// Insert an llvm.dbg.declare into the current block.
DBuilder.insertDeclare(Storage, D, DBuilder.createExpression(Expr),
llvm::DebugLoc::get(Line, Column, Scope),
Builder.GetInsertBlock());
}
return;
}
}

18
clang/test/CodeGenCXX/debug-info-anon-union-vars.cpp
View File

@ -21,8 +21,26 @@ int test_it() {
return (c == 1);
}
void foo() {
union {
int i;
char c;
};
i = 8;
}
// CHECK: [[FILE:.*]] = !DIFile(filename: "{{.*}}debug-info-anon-union-vars.cpp",
// CHECK: !DIGlobalVariable(name: "c",{{.*}} file: [[FILE]], line: 6,{{.*}} isLocal: true, isDefinition: true
// CHECK: !DIGlobalVariable(name: "d",{{.*}} file: [[FILE]], line: 6,{{.*}} isLocal: true, isDefinition: true
// CHECK: !DIGlobalVariable(name: "a",{{.*}} file: [[FILE]], line: 6,{{.*}} isLocal: true, isDefinition: true
// CHECK: !DIGlobalVariable(name: "b",{{.*}} file: [[FILE]], line: 6,{{.*}} isLocal: true, isDefinition: true
// CHECK: !DILocalVariable(tag: DW_TAG_auto_variable, name: "i", {{.*}}, flags: DIFlagArtificial
// CHECK: !DILocalVariable(tag: DW_TAG_auto_variable, name: "c", {{.*}}, flags: DIFlagArtificial
// CHECK: !DILocalVariable(
// CHECK-NOT: name:
// CHECK: type: ![[UNION:[0-9]+]]
// CHECK: ![[UNION]] = !DICompositeType(tag: DW_TAG_union_type,
// CHECK-NOT: name:
// CHECK: elements
// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "i", scope: ![[UNION]],
// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "c", scope: ![[UNION]],