[PATCH] D20541: [esan|cfrag] Create the cfrag variable for the runtime

[Filipe Cabecinhas via llvm-commits]

filcab added a subscriber: filcab.
filcab added a comment.

Please add a test for the cache fragmentation tool's global variable.


================
Comment at: lib/Transforms/Instrumentation/EfficiencySanitizer.cpp:207
@@ +206,3 @@
+  // struct CacheFragTy {
+  //   int         ToolType;
+  //   const char *UnitName;
----------------
I don't really see a reason to include the tool type here. We're already emitting it in the call to `__esan_init`.

================
Comment at: lib/Transforms/Instrumentation/EfficiencySanitizer.cpp:226
@@ +225,3 @@
+                          nullptr));
+  return CacheFragGV;
+}
----------------
I'd rather have a more abstract version of this that just creates an anonymous structure, and then each tool knows what to do with it.
A bit like what UBSan does in clang.

Check out clang's `lib/CodeGen/CGExpr.cpp`
Create the array and then call EmitCheck (line 585):
```
      llvm::Constant *StaticData[] = {
        EmitCheckSourceLocation(E->getLocStart()),
        EmitCheckTypeDescriptor(CalleeType)
      };
      EmitCheck(Checks, "type_mismatch", StaticData, Ptr);
```
In EmitCheck, we have a common way to emit the static args:

```
  // Emit handler arguments and create handler function type.
  if (!StaticArgs.empty()) {
    llvm::Constant *Info = llvm::ConstantStruct::getAnon(StaticArgs);
    auto *InfoPtr =
        new llvm::GlobalVariable(CGM.getModule(), Info->getType(), false,
                                 llvm::GlobalVariable::PrivateLinkage, Info);
    InfoPtr->setUnnamedAddr(true);
    CGM.getSanitizerMetadata()->disableSanitizerForGlobal(InfoPtr);
    Args.push_back(Builder.CreateBitCast(InfoPtr, Int8PtrTy));
    ArgTypes.push_back(Int8PtrTy);
  }
```

That way, each tool can just create the ArrayRef and pass it to a general `createToolGV` or something.

`__esan_init` would get the two args: `ToolType` and a `void*` which is tool specific.


http://reviews.llvm.org/D20541