Simplify Configure in a few ways

 - No need to distinguish between gcc-llvm and clang. First of all,
   gcc-llvm is quite old and surely unmaintained by now. Second of all,
   none of the code actually care about that distinction!

   Now, it does make sense to consider C multiple frontends for LLVMs in
   the form of clang vs clang-cl (same clang, yes, but tweaked
   interface). But this is better handled in terms of "gccish vs
   mvscish" and "is LLVM", yielding 4 combinations. Therefore, I don't
   think it is useful saving the existing code for that.

 - Get the remaining CC_LLVM_BACKEND, and also TABLES_NEXT_TO_CODE in
   mk/config.h the normal way, rather than hacking it post-hoc. No point
   keeping these special cases around for now reason.

 - Get rid of hand-rolled `die` function and just use `AC_MSG_ERROR`.

 - Abstract check + flag override for unregisterised and tables next to
   code.

Oh, and as part of the above I also renamed/combined some variables
where it felt appropriate.

 - GccIsClang -> CcLlvmBackend. This is for `AC_SUBST`, like the other
 Camal case ones. It was never about gcc-llvm, or Apple's renamed clang,
 to be clear.

 - llvm_CC_FLAVOR -> CC_LLVM_BACKEND. This is for `AC_DEFINE`, like the
 other all-caps snake case ones. llvm_CC_FLAVOR was just silly
 indirection *and* an odd name to boot.

5 files changed, 8 insertions, 8 deletions

diff --git a/rts/Task.h b/rts/Task.h
index 88b567ab87..17bcbe2da4 100644
--- a/rts/Task.h
+++ b/rts/Task.h
@@ -271,7 +271,7 @@ extern uint32_t peakWorkerCount;
 #if ((defined(linux_HOST_OS) && \
      (defined(i386_HOST_ARCH) || defined(x86_64_HOST_ARCH))) || \
     (defined(mingw32_HOST_OS) && __GNUC__ >= 4 && __GNUC_MINOR__ >= 4)) && \
-    (!defined(llvm_CC_FLAVOR))
+    (!defined(CC_LLVM_BACKEND))
 #define MYTASK_USE_TLV
 extern __thread Task *my_task;
 #else
diff --git a/rts/ghc.mk b/rts/ghc.mk
index 26865b5bb7..c07cfaec86 100644
--- a/rts/ghc.mk
+++ b/rts/ghc.mk
@@ -523,7 +523,7 @@ rts/win32/ThrIOManager_CC_OPTS += -w
 # for details
 
 # Without this, thread_obj will not be inlined (at least on x86 with GCC 4.1.0)
-ifneq "$(CC_CLANG_BACKEND)" "1"
+ifneq "$(CcLlvmBackend)" "YES"
 rts/sm/Compact_CC_OPTS += -finline-limit=2500
 endif
 
diff --git a/rts/sm/GCTDecl.h b/rts/sm/GCTDecl.h
index 8306795ade..e740392c15 100644
--- a/rts/sm/GCTDecl.h
+++ b/rts/sm/GCTDecl.h
@@ -52,11 +52,11 @@ extern StgWord8 the_gc_thread[];
 
 /* Now, llvm-gcc and some older Clang compilers do not support
    __thread. So we have to fallback to the extremely slow case,
-   unfortunately. Note: clang_CC_FLAVOR implies llvm_CC_FLAVOR.
+   unfortunately.
 
    Also, the iOS Clang compiler doesn't support __thread either for
    some bizarre reason, so there's not much we can do about that... */
-#if defined(llvm_CC_FLAVOR) && (CC_SUPPORTS_TLS == 0)
+#if defined(CC_LLVM_BACKEND) && (CC_SUPPORTS_TLS == 0)
 #define gct ((gc_thread *)(pthread_getspecific(gctKey)))
 #define SET_GCT(to) (pthread_setspecific(gctKey, to))
 #define DECLARE_GCT ThreadLocalKey gctKey;
@@ -66,7 +66,7 @@ extern StgWord8 the_gc_thread[];
 /* However, if we *are* using an LLVM based compiler with __thread
    support, then use that (since LLVM doesn't support global register
    variables.) */
-#elif defined(llvm_CC_FLAVOR) && (CC_SUPPORTS_TLS == 1)
+#elif defined(CC_LLVM_BACKEND) && (CC_SUPPORTS_TLS == 1)
 extern __thread gc_thread* gct;
 #define SET_GCT(to) gct = (to)
 #define DECLARE_GCT __thread gc_thread* gct;
diff --git a/rts/sm/GCThread.h b/rts/sm/GCThread.h
index 66f604d6cc..66f7a7f84f 100644
--- a/rts/sm/GCThread.h
+++ b/rts/sm/GCThread.h
@@ -208,7 +208,7 @@ extern uint32_t n_gc_threads;
 
 extern gc_thread **gc_threads;
 
-#if defined(THREADED_RTS) && defined(llvm_CC_FLAVOR)
+#if defined(THREADED_RTS) && defined(CC_LLVM_BACKEND)
 extern ThreadLocalKey gctKey;
 #endif
 
diff --git a/rts/sm/Storage.c b/rts/sm/Storage.c
index d4be531c73..0130a08f7c 100644
--- a/rts/sm/Storage.c
+++ b/rts/sm/Storage.c
@@ -271,7 +271,7 @@ void storageAddCapabilities (uint32_t from, uint32_t to)
         }
     }
 
-#if defined(THREADED_RTS) && defined(llvm_CC_FLAVOR) && (CC_SUPPORTS_TLS == 0)
+#if defined(THREADED_RTS) && defined(CC_LLVM_BACKEND) && (CC_SUPPORTS_TLS == 0)
     newThreadLocalKey(&gctKey);
 #endif
 
@@ -295,7 +295,7 @@ freeStorage (bool free_heap)
     closeMutex(&sm_mutex);
 #endif
     stgFree(nurseries);
-#if defined(THREADED_RTS) && defined(llvm_CC_FLAVOR) && (CC_SUPPORTS_TLS == 0)
+#if defined(THREADED_RTS) && defined(CC_LLVM_BACKEND) && (CC_SUPPORTS_TLS == 0)
     freeThreadLocalKey(&gctKey);
 #endif
     freeGcThreads();