IR: Introduce llvm.type.checked.load intrinsic.

This intrinsic safely loads a function pointer from a virtual table pointer
using type metadata. This intrinsic is used to implement control flow integrity
in conjunction with virtual call optimization. The virtual call optimization
pass will optimize away llvm.type.checked.load intrinsics associated with
devirtualized calls, thereby removing the type check in cases where it is
not needed to enforce the control flow integrity constraint.

This patch also introduces the capability to copy type metadata between
global variables, and teaches the virtual call optimization pass to do so.

Differential Revision: http://reviews.llvm.org/D21121

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273756 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 15 insertions, 3 deletions

diff --git a/include/llvm/Analysis/TypeMetadataUtils.h b/include/llvm/Analysis/TypeMetadataUtils.h
index 49607874edc..c3f688f5d7f 100644
--- a/include/llvm/Analysis/TypeMetadataUtils.h
+++ b/include/llvm/Analysis/TypeMetadataUtils.h
@@ -30,9 +30,16 @@ struct DevirtCallSite {
 
 /// Given a call to the intrinsic @llvm.type.test, find all devirtualizable
 /// call sites based on the call and return them in DevirtCalls.
-void findDevirtualizableCalls(SmallVectorImpl<DevirtCallSite> &DevirtCalls,
-                              SmallVectorImpl<CallInst *> &Assumes,
-                              CallInst *CI);
+void findDevirtualizableCallsForTypeTest(
+    SmallVectorImpl<DevirtCallSite> &DevirtCalls,
+    SmallVectorImpl<CallInst *> &Assumes, CallInst *CI);
+
+/// Given a call to the intrinsic @llvm.type.checked.load, find all
+/// devirtualizable call sites based on the call and return them in DevirtCalls.
+void findDevirtualizableCallsForTypeCheckedLoad(
+    SmallVectorImpl<DevirtCallSite> &DevirtCalls,
+    SmallVectorImpl<Instruction *> &LoadedPtrs,
+    SmallVectorImpl<Instruction *> &Preds, bool &HasNonCallUses, CallInst *CI);
 }
 
 #endif
diff --git a/include/llvm/IR/Intrinsics.td b/include/llvm/IR/Intrinsics.td
index fdda4e2eeb2..b50f07f3263 100644
--- a/include/llvm/IR/Intrinsics.td
+++ b/include/llvm/IR/Intrinsics.td
@@ -667,6 +667,11 @@ def int_masked_scatter: Intrinsic<[],
 def int_type_test : Intrinsic<[llvm_i1_ty], [llvm_ptr_ty, llvm_metadata_ty],
                               [IntrNoMem]>;
 
+// Safely loads a function pointer from a virtual table pointer using type metadata.
+def int_type_checked_load : Intrinsic<[llvm_ptr_ty, llvm_i1_ty],
+                                      [llvm_ptr_ty, llvm_i32_ty, llvm_metadata_ty],
+                                      [IntrNoMem]>;
+
 def int_load_relative: Intrinsic<[llvm_ptr_ty], [llvm_ptr_ty, llvm_anyint_ty],
                                  [IntrReadMem, IntrArgMemOnly]>;