[Modules] Make Support/Debug.h modular. This requires it to not change

behavior based on other files defining DEBUG_TYPE, which means it cannot
define DEBUG_TYPE at all. This is actually better IMO as it forces folks
to define relevant DEBUG_TYPEs for their files. However, it requires all
files that currently use DEBUG(...) to define a DEBUG_TYPE if they don't
already. I've updated all such files in LLVM and will do the same for
other upstream projects.

This still leaves one important change in how LLVM uses the DEBUG_TYPE
macro going forward: we need to only define the macro *after* header
files have been #include-ed. Previously, this wasn't possible because
Debug.h required the macro to be pre-defined. This commit removes that.
By defining DEBUG_TYPE after the includes two things are fixed:

- Header files that need to provide a DEBUG_TYPE for some inline code
  can do so by defining the macro before their inline code and undef-ing
  it afterward so the macro does not escape.

- We no longer have rampant ODR violations due to including headers with
  different DEBUG_TYPE definitions. This may be mostly an academic
  violation today, but with modules these types of violations are easy
  to check for and potentially very relevant.

Where necessary to suppor headers with DEBUG_TYPE, I have moved the
definitions below the includes in this commit. I plan to move the rest
of the DEBUG_TYPE macros in LLVM in subsequent commits; this one is big
enough.

The comments in Debug.h, which were hilariously out of date already,
have been updated to reflect the recommended practice going forward.

llvm-svn: 206822

3 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp b/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp
index 35fa1aa0d08..2ffe12bd327 100644
--- a/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp
@@ -39,6 +39,8 @@
 
 using namespace llvm;
 
+#define DEBUG_TYPE "hexagon-lowering"
+
 static cl::opt<bool>
 EmitJumpTables("hexagon-emit-jump-tables", cl::init(true), cl::Hidden,
                cl::desc("Control jump table emission on Hexagon target"));
diff --git a/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp b/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
index 21a12def3a3..5c9c80f9d36 100644
--- a/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
@@ -33,6 +33,8 @@
 
 using namespace llvm;
 
+#define DEBUG_TYPE "hexagon-instrinfo"
+
 ///
 /// Constants for Hexagon instructions.
 ///
diff --git a/llvm/lib/Target/Hexagon/HexagonSubtarget.cpp b/llvm/lib/Target/Hexagon/HexagonSubtarget.cpp
index fca67073ef3..70c87fa19d1 100644
--- a/llvm/lib/Target/Hexagon/HexagonSubtarget.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonSubtarget.cpp
@@ -18,6 +18,8 @@
 #include "llvm/Support/ErrorHandling.h"
 using namespace llvm;
 
+#define DEBUG_TYPE "hexagon-subtarget"
+
 #define GET_SUBTARGETINFO_CTOR
 #define GET_SUBTARGETINFO_TARGET_DESC
 #include "HexagonGenSubtargetInfo.inc"