Include llvm-config.h from Demangle/Compiler.h

[andrew.w.kaylor]

Summary

This fixes a problem that was exposed by the recently added ItaniumDemangleTest.cpp unittest.

The problem is that Demangle/Compiler.h checks LLVM_ENABLE_DUMP to see how it should define LLVM_DUMP_METHOD, but it doesn't include llvm-config.h so LLVM_ENABLE_DUMP is always undefined. If you have a build that defines LLVM_ENABLE_DUMP and NDEBUG, then Demangle/Compiler.h and Support/Compiler.h will define LLVM_DUMP_METHOD differently.

You can see this by configuring this way:

cmake -DLLVM_ENABLE_DUMP=true -DCMAKE_BUILD_TYPE="Release" -DLLVM_ENABLE_WERROR=true ../llvm

It isn't clear to me whether or not including llvm-config.h introduces a layering issue, hence the review for a one line change.

[erik.pilkington]

FYI: this will be fixed by https://reviews.llvm.org/D53538 when that lands.

[andrew.w.kaylor]

In D53678#1275140, @erik.pilkington wrote:

FYI: this will be fixed by https://reviews.llvm.org/D53538 when that lands.

In that case, nevermind. I can put a temporary fix in our local tree and wait for the refactoring. Thanks!

include/llvm/Demangle/Compiler.h

 //===--- Compiler.h ---------------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //
 // This file contains a variety of feature test macros copied from
 // include/llvm/Support/Compiler.h so that LLVMDemangle does not need to take
 // a dependency on LLVMSupport.
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_DEMANGLE_COMPILER_H
 #define LLVM_DEMANGLE_COMPILER_H
 
+#include "llvm/Config/llvm-config.h"
+
 #ifdef _MSC_VER
 // snprintf is implemented in VS 2015
 #if _MSC_VER < 1900
 #define snprintf _snprintf_s
 #endif
 #endif
 
 #ifndef __has_feature