Add file containing extensions of the LLVM C API.

Author: Andres Freund
Discussion: https://postgr.es/m/20170901064131.tazjxwus3k2w3ybh@alap3.anarazel.de

src/backend/jit/llvm/Makefile

@@ -37,7 +37,7 @@ override COMPILER = $(CXX) $(CFLAGS)
 OBJS=$(WIN32RES)
 
 # Infrastructure
-OBJS += llvmjit.o llvmjit_error.o
+OBJS += llvmjit.o llvmjit_error.o llvmjit_wrap.o
 # Code generation
 OBJS +=
 

src/backend/jit/llvm/llvmjit_wrap.cpp

+/*-------------------------------------------------------------------------
+ *
+ * llvmjit_wrap.cpp
+ *	  Parts of the LLVM interface not (yet) exposed to C.
+ *
+ * Copyright (c) 2016-2018, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/lib/llvm/llvmjit_wrap.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+extern "C"
+{
+#include "postgres.h"
+}
+
+#include <llvm/MC/SubtargetFeature.h>
+#include <llvm/Support/Host.h>
+
+#include "jit/llvmjit.h"
+
+
+/*
+ * C-API extensions.
+ */
+#if defined(HAVE_DECL_LLVMGETHOSTCPUNAME) && !HAVE_DECL_LLVMGETHOSTCPUNAME
+char *LLVMGetHostCPUName(void) {
+	return strdup(llvm::sys::getHostCPUName().data());
+}
+#endif
+
+
+char *LLVMGetHostCPUFeatures(void) {
+	llvm::SubtargetFeatures Features;
+	llvm::StringMap<bool> HostFeatures;
+
+	if (llvm::sys::getHostCPUFeatures(HostFeatures))
+		for (auto &F : HostFeatures)
+			Features.AddFeature(F.first(), F.second);
+
+	return strdup(Features.getString().c_str());
+}

src/include/jit/llvmjit.h

@@ -44,6 +44,23 @@ extern void llvm_assert_in_fatal_section(void);
 
 extern LLVMJitContext *llvm_create_context(int jitFlags);
 
+
+/*
+ ****************************************************************************
+ * Extensions / Backward compatibility section of the LLVM C API
+ * Error handling related functions.
+ ****************************************************************************
+ */
+#if defined(HAVE_DECL_LLVMGETHOSTCPUNAME) && !HAVE_DECL_LLVMGETHOSTCPUNAME
+/** Get the host CPU as a string. The result needs to be disposed with
+  LLVMDisposeMessage. */
+extern char *LLVMGetHostCPUName(void);
+#endif
+
+/** Get the host CPU features as a string. The result needs to be disposed
+  with LLVMDisposeMessage. */
+extern char *LLVMGetHostCPUFeatures(void);
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif