1 files changed, 25 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/StackProtector.cpp b/llvm/lib/CodeGen/StackProtector.cpp
index 2fe9c7ed5c6..1753eda56d8 100644
--- a/llvm/lib/CodeGen/StackProtector.cpp
+++ b/llvm/lib/CodeGen/StackProtector.cpp
@@ -18,6 +18,7 @@
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/Analysis/EHPersonalities.h"
+#include "llvm/Analysis/OptimizationDiagnosticInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/StackProtector.h"
 #include "llvm/IR/Attributes.h"
@@ -58,7 +59,7 @@ static cl::opt<bool> EnableSelectionDAGSP("enable-selectiondag-sp",
 
 char StackProtector::ID = 0;
 INITIALIZE_TM_PASS(StackProtector, "stack-protector", "Insert stack protectors",
-                false, true)
+                   false, true)
 
 FunctionPass *llvm::createStackProtectorPass(const TargetMachine *TM) {
   return new StackProtector(TM);
@@ -229,7 +230,17 @@ bool StackProtector::RequiresStackProtector() {
   if (F->hasFnAttribute(Attribute::SafeStack))
     return false;
 
+  // We are constructing the OptimizationRemarkEmitter on the fly rather than
+  // using the analysis pass to avoid building DominatorTree and LoopInfo which
+  // are not available this late in the IR pipeline.
+  OptimizationRemarkEmitter ORE(F);
+  auto ReasonStub =
+      Twine("Stack protection applied to function " + F->getName() + " due to ")
+          .str();
+
   if (F->hasFnAttribute(Attribute::StackProtectReq)) {
+    ORE.emit(OptimizationRemark(DEBUG_TYPE, "StackProtectorRequested", F)
+             << ReasonStub << "a function attribute or command-line switch");
     NeedsProtector = true;
     Strong = true; // Use the same heuristic as strong to determine SSPLayout
   } else if (F->hasFnAttribute(Attribute::StackProtectStrong))
@@ -243,20 +254,27 @@ bool StackProtector::RequiresStackProtector() {
     for (const Instruction &I : BB) {
       if (const AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
         if (AI->isArrayAllocation()) {
+          OptimizationRemark Remark(DEBUG_TYPE, "StackProtectorAllocaOrArray",
+                                    &I);
+          Remark << ReasonStub
+                 << "a call to alloca or use of a variable length array";
           if (const auto *CI = dyn_cast<ConstantInt>(AI->getArraySize())) {
             if (CI->getLimitedValue(SSPBufferSize) >= SSPBufferSize) {
               // A call to alloca with size >= SSPBufferSize requires
               // stack protectors.
               Layout.insert(std::make_pair(AI, SSPLK_LargeArray));
+              ORE.emit(Remark);
               NeedsProtector = true;
             } else if (Strong) {
               // Require protectors for all alloca calls in strong mode.
               Layout.insert(std::make_pair(AI, SSPLK_SmallArray));
+              ORE.emit(Remark);
               NeedsProtector = true;
             }
           } else {
             // A call to alloca with a variable size requires protectors.
             Layout.insert(std::make_pair(AI, SSPLK_LargeArray));
+            ORE.emit(Remark);
             NeedsProtector = true;
           }
           continue;
@@ -266,6 +284,9 @@ bool StackProtector::RequiresStackProtector() {
         if (ContainsProtectableArray(AI->getAllocatedType(), IsLarge, Strong)) {
           Layout.insert(std::make_pair(AI, IsLarge ? SSPLK_LargeArray
                                                    : SSPLK_SmallArray));
+          ORE.emit(OptimizationRemark(DEBUG_TYPE, "StackProtectorBuffer", &I)
+                   << ReasonStub
+                   << "a stack allocated buffer or struct containing a buffer");
           NeedsProtector = true;
           continue;
         }
@@ -273,6 +294,9 @@ bool StackProtector::RequiresStackProtector() {
         if (Strong && HasAddressTaken(AI)) {
           ++NumAddrTaken;
           Layout.insert(std::make_pair(AI, SSPLK_AddrOf));
+          ORE.emit(
+              OptimizationRemark(DEBUG_TYPE, "StackProtectorAddressTaken", &I)
+              << ReasonStub << "the address of a local variable being taken");
           NeedsProtector = true;
         }
       }