[PATCH] D13954: CodeGen: Fix LLVM assertion if Swift and Clang emit Objective-C class reference in same LLVM module
Slava Pestov via cfe-commits
cfe-commits at lists.llvm.org
Sat Oct 24 00:00:55 PDT 2015
Unfortunately the asm label attribute doesn’t seem to work in this case, at least on Darwin. I get two symbols in the IR, with the asm label having the \01 prefix from MangleContext::mangleName():
@"\01OBJC_CLASS_$_NSNumber" = common global %struct.art_class* null, align 8
@"OBJC_CLASS_$_NSNumber" = external global %struct._class_t
As for the diagnostic, is this what you had in mind?
commit 4d4f15ffc4d6a72357fa4cee8e2197a03afe6b51
Author: Slava Pestov <spestov at apple.com>
Date: Fri Oct 23 23:57:56 2015 -0700
CodeGen: More robust handling of type conflicts in GetClassGlobal()
diff --git a/lib/CodeGen/CGObjCMac.cpp b/lib/CodeGen/CGObjCMac.cpp
index 31e98b9..e5ef767 100644
--- a/lib/CodeGen/CGObjCMac.cpp
+++ b/lib/CodeGen/CGObjCMac.cpp
@@ -6692,16 +6692,31 @@ CGObjCNonFragileABIMac::GetClassGlobal(const std::string &Name,
llvm::GlobalVariable *GV = CGM.getModule().getGlobalVariable(Name);
- if (!GV)
- GV = new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ClassnfABITy,
- false, L, nullptr, Name);
+ // If it doesn't exist, create it with the right type.
+ if (!GV) {
+ return new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ClassnfABITy,
+ false, L, nullptr, Name);
+ }
assert(GV->getLinkage() == L);
- if (ForDefinition ||
- GV->getValueType() == ObjCTypes.ClassnfABITy)
+ // If it already exists, we might need to bitcast.
+ if (GV->getValueType() == ObjCTypes.ClassnfABITy)
return GV;
+ if (ForDefinition) {
+ DiagnosticsEngine &Diags = CGM.getDiags();
+ unsigned DiagID = Diags.getCustomDiagID(
+ DiagnosticsEngine::Error,
+ "global variable %0 already defined with wrong type");
+ Diags.Report(SourceLocation(), DiagID) << Name;
+
+ // Return a new global in this case, with the right type, since the caller
+ // doesn't expect a constexpr
+ return new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ClassnfABITy,
+ false, L, nullptr, Name);
+ }
+
return llvm::ConstantExpr::getBitCast(GV, ObjCTypes.ClassnfABIPtrTy);
}
> On Oct 21, 2015, at 1:18 PM, John McCall <rjmccall at gmail.com> wrote:
>
> rjmccall added a comment.
>
> It just occurred to me that there is a way to test this in Clang with the asm-label extension:
>
> int Foo_class asm("OBJC_CLASS_$_Foo");
>
> Of course, you'll have to actually use it from somewhere, or define it, in order for it to actually show up in the IR and cause a conflict.
>
> You should probably also test that we do something sane if the caller is making a definition but one already exists. An error counts as "sane"; just make sure you return a GlobalVariable of the right type. There's model code for this in GetOrCreateLLVMFunction, although it's okay for the diagnostic here to be worse than that one.
>
>
> Repository:
> rL LLVM
>
> http://reviews.llvm.org/D13954
>
>
>
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