Set dso_local on cfi_slowpath

[eugenis]

This looks wrong. cfi_slowpath is defined in libclang_rt.cfi, which is linked to the main executable. It is not always dso-local. On Android it is defined in libdl.so and is never dso-local.

[• espindola]

In D45054#1052118, @eugenis wrote:

This looks wrong. cfi_slowpath is defined in libclang_rt.cfi, which is linked to the main executable. It is not always dso-local. On Android it is defined in libdl.so and is never dso-local.

And we don't set cfi_local in that case. See the ITANIUM lines is the testcase.

The CodegenModule functions are named setDSOLocal, setDLLImportDLLExport, etc, but they only set the corresponding flags when appropriate.

[eugenis]

LGTM then. This naming is confusing.

[• espindola]

328836

lib/CodeGen/CGExpr.cpp

void CodeGenFunction::EmitCfiSlowPathCheck(
   llvm::MDNode *Node = MDHelper.createBranchWeights((1U << 20) - 1, 1);
   BI->setMetadata(llvm::LLVMContext::MD_prof, Node);
 
   EmitBlock(CheckBB);
 
   bool WithDiag = !CGM.getCodeGenOpts().SanitizeTrap.has(Kind);
 
   llvm::CallInst *CheckCall;
+  llvm::Constant *SlowPathFn;
   if (WithDiag) {
     llvm::Constant *Info = llvm::ConstantStruct::getAnon(StaticArgs);
     auto *InfoPtr =
         new llvm::GlobalVariable(CGM.getModule(), Info->getType(), false,
                                  llvm::GlobalVariable::PrivateLinkage, Info);
     InfoPtr->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
     CGM.getSanitizerMetadata()->disableSanitizerForGlobal(InfoPtr);
 
-    llvm::Constant *SlowPathDiagFn = CGM.getModule().getOrInsertFunction(
+    SlowPathFn = CGM.getModule().getOrInsertFunction(
         "__cfi_slowpath_diag",
         llvm::FunctionType::get(VoidTy, {Int64Ty, Int8PtrTy, Int8PtrTy},
                                 false));
     CheckCall = Builder.CreateCall(
-        SlowPathDiagFn,
-        {TypeId, Ptr, Builder.CreateBitCast(InfoPtr, Int8PtrTy)});
+        SlowPathFn, {TypeId, Ptr, Builder.CreateBitCast(InfoPtr, Int8PtrTy)});
   } else {
-    llvm::Constant *SlowPathFn = CGM.getModule().getOrInsertFunction(
+    SlowPathFn = CGM.getModule().getOrInsertFunction(
         "__cfi_slowpath",
         llvm::FunctionType::get(VoidTy, {Int64Ty, Int8PtrTy}, false));
     CheckCall = Builder.CreateCall(SlowPathFn, {TypeId, Ptr});
   }
 
+  CGM.setDSOLocal(cast<llvm::GlobalValue>(SlowPathFn->stripPointerCasts()));
   CheckCall->setDoesNotThrow();
 
   EmitBlock(Cont);
 }
 
 // Emit a stub for __cfi_check function so that the linker knows about this
 // symbol in LTO mode.
 void CodeGenFunction::EmitCfiCheckStub() {

test/CodeGen/cfi-icall-cross-dso.c

 // ITANIUM: call i1 @llvm.type.test(i8* %{{.*}}, metadata !"_ZTSFvE"), !nosanitize
 // ITANIUM-DIAG: call void @__cfi_slowpath_diag(i64 6588678392271548388, i8* %{{.*}}, {{.*}}@[[DATA]]{{.*}}) {{.*}}, !nosanitize
 // ITANIUM-TRAP: call void @__cfi_slowpath(i64 6588678392271548388, i8* %{{.*}}) {{.*}}, !nosanitize
 
 // MS: call i1 @llvm.type.test(i8* %{{.*}}, metadata !"?6AX@Z"), !nosanitize
 // MS-DIAG: call void @__cfi_slowpath_diag(i64 4195979634929632483, i8* %{{.*}}, {{.*}}@[[DATA]]{{.*}}) {{.*}}, !nosanitize
 // MS-TRAP: call void @__cfi_slowpath(i64 4195979634929632483, i8* %{{.*}}) {{.*}}, !nosanitize
 
+// ITANIUM-DIAG: declare void @__cfi_slowpath_diag(
+// ITANIUM-TRAP: declare void @__cfi_slowpath(
+// MS-DIAG: declare dso_local void @__cfi_slowpath_diag(
+// MS-TRAP: declare dso_local void @__cfi_slowpath(
+
 void caller(void (*f)()) {
   f();
 }
 
 // Check that we emit both string and hash based type entries for static void g(),
 // and don't emit them for the declaration of h().
 
 // CHECK: define internal void @g({{.*}} !type [[TVOID:![0-9]+]] !type [[TVOID_GENERALIZED:![0-9]+]] !type [[TVOID_ID:![0-9]+]]