added threadfence feature for hcc

1. Added feature for __threadfence and __threadfence_block
2. Added feature for using LLVM IR files directly while compilation
3. Added test for threadfence and threadfence_block

Change-Id: Ib7e5d89b4cca1a135952b317e5809cd05b56a3c9

src/hip_ir.ll

@@ -0,0 +1,15 @@
+target datalayout = "e-p:32:32-p1:64:64-p2:64:64-p3:32:32-p4:64:64-p5:32:32-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64"
+target triple = "amdgcn--amdhsa"
+
+
+define void @__threadfence() #1 {
+    fence syncscope(2) seq_cst
+    ret void
+}
+
+define void @__threadfence_block()  #1 {
+    fence syncscope(3) seq_cst
+    ret void
+}
+
+attributes #1 = { alwaysinline nounwind }