Add a new attribute called 'jumptable' that creates jump-instruction tables for functions marked with this attribute.

It includes a pass that rewrites all indirect calls to jumptable functions to pass through these tables.

This also adds backend support for generating the jump-instruction tables on ARM and X86.
Note that since the jumptable attribute creates a second function pointer for a
function, any function marked with jumptable must also be marked with unnamed_addr.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210280 91177308-0d34-0410-b5e6-96231b3b80d8

test/Bitcode/attributes.ll

@@ -203,7 +203,7 @@ define void @f34()
 ; CHECK: define void @f34()
 {
         call void @nobuiltin() nobuiltin
-; CHECK: call void @nobuiltin() #24
+; CHECK: call void @nobuiltin() #25
         ret void;
 }
 
@@ -223,6 +223,12 @@ define nonnull i8* @f37(i8* nonnull %a) {
         ret i8* %a
 }
 
+define void @f38() unnamed_addr jumptable {
+; CHECK: define void @f38() unnamed_addr #24
+    call void bitcast (void (i8*)* @f36 to void ()*)()
+    unreachable
+}
+
 ; CHECK: attributes #0 = { noreturn }
 ; CHECK: attributes #1 = { nounwind }
 ; CHECK: attributes #2 = { readnone }
@@ -247,5 +253,5 @@ define nonnull i8* @f37(i8* nonnull %a) {
 ; CHECK: attributes #21 = { sspstrong }
 ; CHECK: attributes #22 = { minsize }
 ; CHECK: attributes #23 = { noinline optnone }
-; CHECK: attributes #24 = { nobuiltin }
-
+; CHECK: attributes #24 = { jumptable }
+; CHECK: attributes #25 = { nobuiltin }