RISCV: Start moving runtime libcall config to tablegen

This doesn't yet attempt to move the OS dependent configuration
shared with other targets. Removes __riscv_flush_icache from the
default set so it's no longer falsely reported as available for
other targets.

Author: arsenm

llvm/include/llvm/IR/RuntimeLibcalls.td

@@ -668,7 +668,6 @@ def __llvm_deoptimize : RuntimeLibcallImpl<DEOPTIMIZE>;
 
 // Clear cache
 def __clear_cache : RuntimeLibcallImpl<CLEAR_CACHE>;
-def __riscv_flush_icache : RuntimeLibcallImpl<RISCV_FLUSH_ICACHE>;
 
 //--------------------------------------------------------------------
 // libm
@@ -928,6 +927,8 @@ def bzero : RuntimeLibcallImpl<BZERO>;
 def __bzero : RuntimeLibcallImpl<BZERO>;
 def _Unwind_SjLj_Resume : RuntimeLibcallImpl<UNWIND_RESUME>;
 
+def __riscv_flush_icache : RuntimeLibcallImpl<RISCV_FLUSH_ICACHE>;
+
 //===----------------------------------------------------------------------===//
 // F128 libm Runtime Libcalls
 //===----------------------------------------------------------------------===//
@@ -1846,6 +1847,18 @@ def PPCSystemLibrary
            AvailableIf<memcpy, isNotAIX>,
            LibcallImpls<(add Int128RTLibcalls), isPPC64>)>;
 
+//===----------------------------------------------------------------------===//
+// RISCV Runtime Libcalls
+//===----------------------------------------------------------------------===//
+
+def isRISCV : RuntimeLibcallPredicate<"TT.isRISCV()">;
+def isRISCV64 : RuntimeLibcallPredicate<"TT.isRISCV64()">;
+
+def RISCVSystemLibrary
+    : SystemRuntimeLibrary<isRISCV,
+      (add DefaultRuntimeLibcallImpls, __riscv_flush_icache,
+           LibcallImpls<(add Int128RTLibcalls), isRISCV64>)>;
+
 //===----------------------------------------------------------------------===//
 // SPARC Runtime Libcalls
 //===----------------------------------------------------------------------===//