[stackprotector] Use analysis from the StackProtector pass for stack layout in PEI a nd LocalStackSlot passes.

This changes the MachineFrameInfo API to use the new SSPLayoutKind information
produced by the StackProtector pass (instead of a boolean flag) and updates a
few pass dependencies (to preserve the SSP analysis).

The stack layout follows the same approach used prior to this change - i.e.,
only LargeArray stack objects will be placed near the canary and everything
else will be laid out normally.  After this change, structures containing large
arrays will also be placed near the canary - a case previously missed by the
old implementation.

Out of tree targets will need to update their usage of
MachineFrameInfo::CreateStackObject to remove the MayNeedSP argument. 

The next patch will implement the rules for sspstrong and sspreq.  The end goal
is to support ssp-strong stack layout rules.

WIP.

Differential Revision: http://llvm-reviews.chandlerc.com/D2158

llvm-svn: 197653

1 files changed, 40 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 9e699799912..6a43efbec7e 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -20,6 +20,7 @@
 #include "PrologEpilogInserter.h"
 #include "llvm/ADT/IndexedMap.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/CodeGen/MachineDominators.h"
@@ -30,6 +31,7 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/RegisterScavenging.h"
 #include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/CodeGen/StackProtector.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/Support/CommandLine.h"
@@ -56,6 +58,7 @@ INITIALIZE_PASS_BEGIN(PEI, "prologepilog",
                 "Prologue/Epilogue Insertion", false, false)
 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
+INITIALIZE_PASS_DEPENDENCY(StackProtector)
 INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
 INITIALIZE_PASS_END(PEI, "prologepilog",
                     "Prologue/Epilogue Insertion & Frame Finalization",
@@ -69,6 +72,7 @@ void PEI::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
   AU.addPreserved<MachineLoopInfo>();
   AU.addPreserved<MachineDominatorTree>();
+  AU.addRequired<StackProtector>();
   AU.addRequired<TargetPassConfig>();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
@@ -97,6 +101,9 @@ void PEI::calculateSets(MachineFunction &Fn) {
   return;
 }
 
+/// StackObjSet - A set of stack object indexes
+typedef SmallSetVector<int, 8> StackObjSet;
+
 /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
 /// frame indexes with appropriate references.
 ///
@@ -412,11 +419,28 @@ AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx,
   }
 }
 
+/// AssignProtectedObjSet - Helper function to assign large stack objects (i.e.,
+/// those required to be close to the Stack Protector) to stack offsets.
+static void
+AssignProtectedObjSet(const StackObjSet &UnassignedObjs,
+                      SmallSet<int, 16> &ProtectedObjs,
+                      MachineFrameInfo *MFI, bool StackGrowsDown,
+                      int64_t &Offset, unsigned &MaxAlign) {
+
+  for (StackObjSet::const_iterator I = UnassignedObjs.begin(),
+        E = UnassignedObjs.end(); I != E; ++I) {
+    int i = *I;
+    AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
+    ProtectedObjs.insert(i);
+  }
+}
+
 /// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
 /// abstract stack objects.
 ///
 void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
   const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
+  StackProtector *SP = &getAnalysis<StackProtector>();
 
   bool StackGrowsDown =
     TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
@@ -526,8 +550,9 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
 
   // Make sure that the stack protector comes before the local variables on the
   // stack.
-  SmallSet<int, 16> LargeStackObjs;
+  SmallSet<int, 16> ProtectedObjs;
   if (MFI->getStackProtectorIndex() >= 0) {
+    StackObjSet LargeArrayObjs;
     AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
                       Offset, MaxAlign);
 
@@ -544,12 +569,21 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
         continue;
       if (MFI->getStackProtectorIndex() == (int)i)
         continue;
-      if (!MFI->MayNeedStackProtector(i))
-        continue;
 
-      AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
-      LargeStackObjs.insert(i);
+      switch (SP->getSSPLayout(MFI->getObjectAllocation(i))) {
+      case StackProtector::SSPLK_None:
+      case StackProtector::SSPLK_SmallArray:
+      case StackProtector::SSPLK_AddrOf:
+        continue;
+      case StackProtector::SSPLK_LargeArray:
+        LargeArrayObjs.insert(i);
+        continue;
+      }
+      llvm_unreachable("Unexpected SSPLayoutKind.");
     }
+
+    AssignProtectedObjSet(LargeArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
+                          Offset, MaxAlign);
   }
 
   // Then assign frame offsets to stack objects that are not used to spill
@@ -566,7 +600,7 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
       continue;
     if (MFI->getStackProtectorIndex() == (int)i)
       continue;
-    if (LargeStackObjs.count(i))
+    if (ProtectedObjs.count(i))
       continue;
 
     AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);