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.

llvm-svn: 210280

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index a9074bb294d..58475e2d3cb 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -173,6 +173,8 @@ std::string Attribute::getAsString(bool InAttrGrp) const {
     return "inlinehint";
   if (hasAttribute(Attribute::InReg))
     return "inreg";
+  if (hasAttribute(Attribute::JumpTable))
+    return "jumptable";
   if (hasAttribute(Attribute::MinSize))
     return "minsize";
   if (hasAttribute(Attribute::Naked))
@@ -395,6 +397,7 @@ uint64_t AttributeImpl::getAttrMask(Attribute::AttrKind Val) {
   case Attribute::OptimizeNone:    return 1ULL << 42;
   case Attribute::InAlloca:        return 1ULL << 43;
   case Attribute::NonNull:         return 1ULL << 44;
+  case Attribute::JumpTable:       return 1ULL << 45;
   }
   llvm_unreachable("Unsupported attribute type");
 }