commit dfc2c51d12fd53822279b6e564cdd5cef5c00b46
author Bill Wendling <isanbard@gmail.com> Tue Jul 27 01:55:19 2010 +0000
committer Bill Wendling <isanbard@gmail.com> Tue Jul 27 01:55:19 2010 +0000
tree 28551e2f1fe74455cafc88e6513619690134d9d1
parent ab28928fe276d20cf9533ae6b858497f835c7a53

It's better to have the arrays, which would trigger the creation of stack
protectors, to be near the stack protectors on the stack. Accomplish this by
tagging the stack object with a predicate that indicates that it would trigger
this. In the prolog-epilog inserter, assign these objects to the stack after the
stack protector but before the other objects.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109481 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachineFunction.cpp

diff --git a/lib/CodeGen/MachineFunction.cpp b/lib/CodeGen/MachineFunction.cpp
index 9a52b7b..0171700 100644
--- a/lib/CodeGen/MachineFunction.cpp
+++ b/lib/CodeGen/MachineFunction.cpp
@@ -446,7 +446,7 @@
   unsigned StackAlign = TFI.getStackAlignment();
   unsigned Align = MinAlign(SPOffset, StackAlign);
   Objects.insert(Objects.begin(), StackObject(Size, Align, SPOffset, Immutable,
-                                              /*isSS*/false));
+                                              /*isSS*/false, false));
   return -++NumFixedObjects;
 }
 

lib/CodeGen/PrologEpilogInserter.cpp

diff --git a/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp
index 3787d0b..827b6a3 100644
--- a/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/lib/CodeGen/PrologEpilogInserter.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/ADT/IndexedMap.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/STLExtras.h"
 #include <climits>
 
@@ -549,10 +550,29 @@
 
   // Make sure that the stack protector comes before the local variables on the
   // stack.
-  if (MFI->getStackProtectorIndex() >= 0)
+  SmallSet<int, 16> LargeStackObjs;
+  if (MFI->getStackProtectorIndex() >= 0) {
     AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
                       Offset, MaxAlign);
 
+    // Assign large stack objects first.
+    for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+      if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
+        continue;
+      if (RS && (int)i == RS->getScavengingFrameIndex())
+        continue;
+      if (MFI->isDeadObjectIndex(i))
+        continue;
+      if (MFI->getStackProtectorIndex() == (int)i)
+        continue;
+      if (!MFI->MayNeedStackProtector(i))
+        continue;
+
+      AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
+      LargeStackObjs.insert(i);
+    }
+  }
+
   // Then assign frame offsets to stack objects that are not used to spill
   // callee saved registers.
   for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
@@ -564,6 +584,8 @@
       continue;
     if (MFI->getStackProtectorIndex() == (int)i)
       continue;
+    if (LargeStackObjs.count(i))
+      continue;
 
     AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
   }

lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp

diff --git a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index ee3bc0a..77a2c86 100644
--- a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -112,8 +112,16 @@
 
         TySize *= CUI->getZExtValue();   // Get total allocated size.
         if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.
+
+        // The object may need to be placed onto the stack near the stack
+        // protector if one exists. Determine here if this object is a suitable
+        // candidate. I.e., it would trigger the creation of a stack protector.
+        bool MayNeedSP =
+          (AI->isArrayAllocation() ||
+           (TySize > 8 && isa<ArrayType>(Ty) &&
+            cast<ArrayType>(Ty)->getElementType()->isIntegerTy(8)));
         StaticAllocaMap[AI] =
-          MF->getFrameInfo()->CreateStackObject(TySize, Align, false);
+          MF->getFrameInfo()->CreateStackObject(TySize, Align, false, MayNeedSP);
       }
 
   for (; BB != EB; ++BB)