Add Windows Control Flow Guard checks (/guard:cf).

Summary:
A new function pass (Transforms/CFGuard/CFGuard.cpp) inserts CFGuard checks on
indirect function calls, using either the check mechanism (X86, ARM, AArch64) or
or the dispatch mechanism (X86-64). The check mechanism requires a new calling
convention for the supported targets. The dispatch mechanism adds the target as
an operand bundle, which is processed by SelectionDAG. Another pass
(CodeGen/CFGuardLongjmp.cpp) identifies and emits valid longjmp targets, as
required by /guard:cf. This feature is enabled using the `cfguard` CC1 option.

Reviewers: thakis, rnk, theraven, pcc

Subscribers: ychen, hans, metalcanine, dmajor, tomrittervg, alex, mehdi_amini, mgorny, javed.absar, kristof.beyls, hiraditya, steven_wu, dexonsmith, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D65761

1 files changed, 5 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 75708d6e496..480a33f2728 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -482,8 +482,11 @@ void CodeGenModule::Release() {
     getModule().addModuleFlag(llvm::Module::Warning, "CodeViewGHash", 1);
   }
   if (CodeGenOpts.ControlFlowGuard) {
-    // We want function ID tables for Control Flow Guard.
-    getModule().addModuleFlag(llvm::Module::Warning, "cfguardtable", 1);
+    // Function ID tables and checks for Control Flow Guard (cfguard=2).
+    getModule().addModuleFlag(llvm::Module::Warning, "cfguard", 2);
+  } else if (CodeGenOpts.ControlFlowGuardNoChecks) {
+    // Function ID tables for Control Flow Guard (cfguard=1).
+    getModule().addModuleFlag(llvm::Module::Warning, "cfguard", 1);
   }
   if (CodeGenOpts.OptimizationLevel > 0 && CodeGenOpts.StrictVTablePointers) {
     // We don't support LTO with 2 with different StrictVTablePointers