[llvm] r373216 - [SSP] [1/3] Revert "StackProtector: Use PointerMayBeCaptured"

[Paul Robinson via llvm-commits]

Author: probinson
Date: Mon Sep 30 08:01:35 2019
New Revision: 373216

URL: http://llvm.org/viewvc/llvm-project?rev=373216&view=rev
Log:
[SSP] [1/3] Revert "StackProtector: Use PointerMayBeCaptured"
"Captured" and "relevant to Stack Protector" are not the same thing.

This reverts commit f29366b1f594f48465c5a2754bcffac6d70fd0b1.
aka r363169.

Differential Revision: https://reviews.llvm.org/D67842

Removed:
    llvm/trunk/test/Transforms/StackProtector/
Modified:
    llvm/trunk/include/llvm/CodeGen/StackProtector.h
    llvm/trunk/lib/CodeGen/StackProtector.cpp
    llvm/trunk/test/CodeGen/X86/stack-protector.ll
    llvm/trunk/tools/opt/opt.cpp

Modified: llvm/trunk/include/llvm/CodeGen/StackProtector.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/StackProtector.h?rev=373216&r1=373215&r2=373216&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/StackProtector.h (original)
+++ llvm/trunk/include/llvm/CodeGen/StackProtector.h Mon Sep 30 08:01:35 2019
@@ -61,6 +61,12 @@ private:
   /// protection when -fstack-protection is used.
   unsigned SSPBufferSize = 0;
 
+  /// VisitedPHIs - The set of PHI nodes visited when determining
+  /// if a variable's reference has been taken.  This set
+  /// is maintained to ensure we don't visit the same PHI node multiple
+  /// times.
+  SmallPtrSet<const PHINode *, 16> VisitedPHIs;
+
   // A prologue is generated.
   bool HasPrologue = false;
 

Modified: llvm/trunk/lib/CodeGen/StackProtector.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/StackProtector.cpp?rev=373216&r1=373215&r2=373216&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/StackProtector.cpp (original)
+++ llvm/trunk/lib/CodeGen/StackProtector.cpp Mon Sep 30 08:01:35 2019
@@ -17,7 +17,6 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/BranchProbabilityInfo.h"
-#include "llvm/Analysis/CaptureTracking.h"
 #include "llvm/Analysis/EHPersonalities.h"
 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
 #include "llvm/CodeGen/Passes.h"
@@ -157,6 +156,40 @@ bool StackProtector::ContainsProtectable
   return NeedsProtector;
 }
 
+bool StackProtector::HasAddressTaken(const Instruction *AI) {
+  for (const User *U : AI->users()) {
+    if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
+      if (AI == SI->getValueOperand())
+        return true;
+    } else if (const PtrToIntInst *SI = dyn_cast<PtrToIntInst>(U)) {
+      if (AI == SI->getOperand(0))
+        return true;
+    } else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
+      // Ignore intrinsics that are not calls. TODO: Use isLoweredToCall().
+      if (!isa<DbgInfoIntrinsic>(CI) && !CI->isLifetimeStartOrEnd())
+        return true;
+    } else if (isa<InvokeInst>(U)) {
+      return true;
+    } else if (const SelectInst *SI = dyn_cast<SelectInst>(U)) {
+      if (HasAddressTaken(SI))
+        return true;
+    } else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
+      // Keep track of what PHI nodes we have already visited to ensure
+      // they are only visited once.
+      if (VisitedPHIs.insert(PN).second)
+        if (HasAddressTaken(PN))
+          return true;
+    } else if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
+      if (HasAddressTaken(GEP))
+        return true;
+    } else if (const BitCastInst *BI = dyn_cast<BitCastInst>(U)) {
+      if (HasAddressTaken(BI))
+        return true;
+    }
+  }
+  return false;
+}
+
 /// Search for the first call to the llvm.stackprotector intrinsic and return it
 /// if present.
 static const CallInst *findStackProtectorIntrinsic(Function &F) {
@@ -264,9 +297,7 @@ bool StackProtector::RequiresStackProtec
           continue;
         }
 
-        if (Strong && PointerMayBeCaptured(AI,
-                                           /* ReturnCaptures */ false,
-                                           /* StoreCaptures */ true)) {
+        if (Strong && HasAddressTaken(AI)) {
           ++NumAddrTaken;
           Layout.insert(std::make_pair(AI, MachineFrameInfo::SSPLK_AddrOf));
           ORE.emit([&]() {

Modified: llvm/trunk/test/CodeGen/X86/stack-protector.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/stack-protector.ll?rev=373216&r1=373215&r2=373216&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/stack-protector.ll (original)
+++ llvm/trunk/test/CodeGen/X86/stack-protector.ll Mon Sep 30 08:01:35 2019
@@ -4087,8 +4087,8 @@ define i32 @IgnoreIntrinsicTest() #1 {
   %1 = alloca i32, align 4
   %2 = bitcast i32* %1 to i8*
   call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %2)
-  store i32 1, i32* %1, align 4
-  %3 = load i32, i32* %1, align 4
+  store volatile i32 1, i32* %1, align 4
+  %3 = load volatile i32, i32* %1, align 4
   %4 = mul nsw i32 %3, 42
   call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %2)
   ret i32 %4

Modified: llvm/trunk/tools/opt/opt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/opt/opt.cpp?rev=373216&r1=373215&r2=373216&view=diff
==============================================================================
--- llvm/trunk/tools/opt/opt.cpp (original)
+++ llvm/trunk/tools/opt/opt.cpp Mon Sep 30 08:01:35 2019
@@ -523,7 +523,6 @@ int main(int argc, char **argv) {
   initializeDwarfEHPreparePass(Registry);
   initializeSafeStackLegacyPassPass(Registry);
   initializeSjLjEHPreparePass(Registry);
-  initializeStackProtectorPass(Registry);
   initializePreISelIntrinsicLoweringLegacyPassPass(Registry);
   initializeGlobalMergePass(Registry);
   initializeIndirectBrExpandPassPass(Registry);