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, 10 insertions, 1 deletions

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 6da8014a22d..46beb13622d 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -735,7 +735,8 @@ void Verifier::VerifyAttributeTypes(AttributeSet Attrs, unsigned Idx,
         I->getKindAsEnum() == Attribute::Builtin ||
         I->getKindAsEnum() == Attribute::NoBuiltin ||
         I->getKindAsEnum() == Attribute::Cold ||
-        I->getKindAsEnum() == Attribute::OptimizeNone) {
+        I->getKindAsEnum() == Attribute::OptimizeNone ||
+        I->getKindAsEnum() == Attribute::JumpTable) {
       if (!isFunction) {
         CheckFailed("Attribute '" + I->getAsString() +
                     "' only applies to functions!", V);
@@ -909,6 +910,14 @@ void Verifier::VerifyFunctionAttrs(FunctionType *FT, AttributeSet Attrs,
                                 Attribute::MinSize),
             "Attributes 'minsize and optnone' are incompatible!", V);
   }
+
+  if (Attrs.hasAttribute(AttributeSet::FunctionIndex,
+                         Attribute::JumpTable)) {
+    const GlobalValue *GV = cast<GlobalValue>(V);
+    Assert1(GV->hasUnnamedAddr(),
+            "Attribute 'jumptable' requires 'unnamed_addr'", V);
+
+  }
 }
 
 void Verifier::VerifyBitcastType(const Value *V, Type *DestTy, Type *SrcTy) {