Module Debugging: Use a nonzero DWO id for precompiled headers.
PCH files don't have a module signature and LLVM uses a nonzero DWO id as
an indicator for skeleton / module CUs. This change pins the DWO id for PCH
files to a known constant value.
The correct long-term solution here is to implement a module signature
that is an actual dterministic hash (at the moment module signatures are
just random nonzero numbers) and then enable this for PCH files as well.
<rdar://problem/24290667>
llvm-svn: 258507
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 28e2848..4e0cc3f 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -1740,11 +1740,14 @@
bool IsRootModule = M ? !M->Parent : true;
if (CreateSkeletonCU && IsRootModule) {
+ // PCH files don't have a signature field in the control block,
+ // but LLVM detects skeleton CUs by looking for a non-zero DWO id.
+ uint64_t Signature = Mod.getSignature() ? Mod.getSignature() : ~1U;
llvm::DIBuilder DIB(CGM.getModule());
DIB.createCompileUnit(TheCU->getSourceLanguage(), Mod.getModuleName(),
Mod.getPath(), TheCU->getProducer(), true,
StringRef(), 0, Mod.getASTFile(),
- llvm::DIBuilder::FullDebug, Mod.getSignature());
+ llvm::DIBuilder::FullDebug, Signature);
DIB.finalize();
}
llvm::DIModule *Parent =
diff --git a/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp b/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
index cd17832..2178ec2 100644
--- a/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
+++ b/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
@@ -219,7 +219,11 @@
M->setTargetTriple(Ctx.getTargetInfo().getTriple().getTriple());
M->setDataLayout(Ctx.getTargetInfo().getDataLayoutString());
- Builder->getModuleDebugInfo()->setDwoId(Buffer->Signature);
+
+ // PCH files don't have a signature field in the control block,
+ // but LLVM detects DWO CUs by looking for a non-zero DWO id.
+ uint64_t Signature = Buffer->Signature ? Buffer->Signature : ~1U;
+ Builder->getModuleDebugInfo()->setDwoId(Signature);
// Finalize the Builder.
if (Builder)