[OCaml] introduce link_gc_components

[artagnon]

Summary

set_gc (Some "shadow-stack") f works fine in a program that links to llvm.gc and calls link_gc_components.

[artagnon]

The issue with making it part of the llvm package is that it gets
executed as soon as the package is loaded. The closest equivalent to
including an optional header in the C++ world is compiling with an
optional package in the OCaml world.

Make a minimal gc package that should be filled in with details later,
as the gc develops.

[artagnon]

Make it a little less minimalist to cover more usecases, add missing C
file.

[artagnon]

Rebase onto latest master.

bindings/ocaml/CMakeLists.txt

 add_subdirectory(llvm)
 add_subdirectory(all_backends)
 add_subdirectory(analysis)
 add_subdirectory(backends)
 add_subdirectory(bitreader)
 add_subdirectory(bitwriter)
+add_subdirectory(gc)
 add_subdirectory(irreader)
 add_subdirectory(linker)
 add_subdirectory(target)
 add_subdirectory(transforms)
 add_subdirectory(executionengine)

bindings/ocaml/Makefile

 ##===- bindings/ocaml/Makefile -----------------------------*- Makefile -*-===##
 #
 #                     The LLVM Compiler Infrastructure
 #
 # This file is distributed under the University of Illinois Open Source
 # License. See LICENSE.TXT for details.
 #
 ##===----------------------------------------------------------------------===##
 
 LEVEL := ../..
 DIRS = llvm bitreader bitwriter irreader analysis target executionengine \
-       transforms linker backends all_backends
+       transforms linker backends all_backends gc
 ExtraMakefiles = $(PROJ_OBJ_DIR)/Makefile.ocaml
 
 ocamldoc:
   $(Verb) for i in $(DIRS) ; do \
     $(MAKE) -C $$i ocamldoc; \
   done
 
 include $(LEVEL)/Makefile.common

bindings/ocaml/gc/CMakeLists.txt

+add_ocaml_library(llvm_gc
+  OCAML    llvm_gc
+  OCAMLDEP llvm
+  C        gc_ocaml
+  LLVM     codegen)

bindings/ocaml/gc/Makefile

+##===- bindings/ocaml/gc/Makefile --------------------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+LEVEL := ../../..
+LIBRARYNAME := llvm_gc
+UsedComponents := codegen
+UsedOcamlInterfaces := llvm
+
+include ../Makefile.ocaml

bindings/ocaml/gc/gc_ocaml.c

+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include "llvm-c/Core.h"
+#include "caml/alloc.h"
+#include "caml/custom.h"
+#include "caml/fail.h"
+#include "caml/memory.h"
+#include "caml/callback.h"
+
+/* unit -> unit */
+CAMLprim value llvm_link_gc_components(value Unit) {
+  LLVMLinkGCComponents();
+  return Val_unit;
+}

bindings/ocaml/gc/llvm_gc.ml

+external link_gc_components : unit -> unit = "llvm_link_gc_components"

bindings/ocaml/gc/llvm_gc.mli

+(** [link_gc_components] links up up CodeGen and AsmWriter components
+    related to GC. After a call to this function, ErlangGC, OCamlGC,
+    and ShadowStackGC will be accessible. See the method
+    [LLVMLinkGCComponents]. *)
+val link_gc_components : unit -> unit

bindings/ocaml/llvm/META.llvm.in

 package "executionengine" (
     requires = "llvm,llvm.target,ctypes.foreign"
     version = "@PACKAGE_VERSION@"
     description = "JIT and Interpreter for LLVM"
     archive(byte) = "llvm_executionengine.cma"
     archive(native) = "llvm_executionengine.cmxa"
 )
 
+package "gc" (
+    requires = "llvm"
+    version = "@PACKAGE_VERSION@"
+    description = "GC support for LLVM JIT"
+    archive(byte) = "llvm_gc.cma"
+    archive(native) = "llvm_gc.cmxa"
+)
+
 package "ipo" (
     requires = "llvm"
     version  = "@PACKAGE_VERSION@"
     description = "IPO Transforms for LLVM"
     archive(byte) = "llvm_ipo.cma"
     archive(native) = "llvm_ipo.cmxa"
 )
 

include/llvm-c/Core.h

  * @see llvm::Function::setCallingConv()
  *
  * @param Fn Function to operate on
  * @param CC LLVMCallConv to set calling convention to
  */
 void LLVMSetFunctionCallConv(LLVMValueRef Fn, unsigned CC);
 
 /**
+ * Link the Codegen and AsmWriter components related to GC. After a
+ * call to this function, ErlangGC, OCamlGC and ShadowStackGC will be
+ * accessible.
+ *
+ */
+void LLVMLinkGCComponents(void);
+
+/**
  * Obtain the name of the garbage collector to use during code
  * generation.
  *
  * @see llvm::Function::getGC()
  */
 const char *LLVMGetGC(LLVMValueRef Fn);
 
 /**

lib/CodeGen/CMakeLists.txt

add_llvm_library(LLVMCodeGen
   IfConversion.cpp
   InlineSpiller.cpp
   InterferenceCache.cpp
   IntrinsicLowering.cpp
   JumpInstrTables.cpp
   LLVMTargetMachine.cpp
   LatencyPriorityQueue.cpp
   LexicalScopes.cpp
+  LinkGCComponents.cpp
   LiveDebugVariables.cpp
   LiveInterval.cpp
   LiveIntervalAnalysis.cpp
   LiveIntervalUnion.cpp
   LiveRangeCalc.cpp
   LiveRangeEdit.cpp
   LiveRegMatrix.cpp
   LivePhysRegs.cpp

lib/CodeGen/LinkGCComponents.cpp

+#include "llvm/CodeGen/LinkAllCodegenComponents.h"
+#include "llvm/CodeGen/LinkAllAsmWriterComponents.h"
+
+extern "C" void LLVMLinkGCComponents() {}