Teach MachineFrameInfo to track maximum alignment while stack objects are being

created. This ensures it's updated at all time. It means targets which perform
dynamic stack alignment would know whether it is required and whether frame
pointer register cannot be made available register allocation.
This is a fix for rdar://7625239. Sorry, I can't create a reasonably sized test
case.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96069 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 13 deletions

diff --git a/include/llvm/CodeGen/MachineFrameInfo.h b/include/llvm/CodeGen/MachineFrameInfo.h
index 968e4ea..043e97f 100644
--- a/include/llvm/CodeGen/MachineFrameInfo.h
+++ b/include/llvm/CodeGen/MachineFrameInfo.h
@@ -276,6 +276,7 @@ public:
     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
            "Invalid Object Idx!");
     Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
+    MaxAlignment = std::max(MaxAlignment, Align);
   }
 
   /// getObjectOffset - Return the assigned stack offset of the specified object
@@ -328,19 +329,6 @@ public:
   ///
   void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
 
-  /// calculateMaxStackAlignment() - If there is a local object which requires
-  /// greater alignment than the current max alignment, adjust accordingly.
-  void calculateMaxStackAlignment() {
-    for (int i = getObjectIndexBegin(),
-         e = getObjectIndexEnd(); i != e; ++i) {
-      if (isDeadObjectIndex(i))
-        continue;
-
-      unsigned Align = getObjectAlignment(i);
-      MaxAlignment = std::max(MaxAlignment, Align);
-    }
-  }
-
   /// hasCalls - Return true if the current function has no function calls.
   /// This is only valid during or after prolog/epilog code emission.
   ///
@@ -402,6 +390,7 @@ public:
     Objects.push_back(StackObject(Size, Alignment, 0, false, isSS));
     int Index = (int)Objects.size()-NumFixedObjects-1;
     assert(Index >= 0 && "Bad frame index!");
+    MaxAlignment = std::max(MaxAlignment, Alignment);
     return Index;
   }
 
@@ -412,6 +401,7 @@ public:
   int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
     CreateStackObject(Size, Alignment, true);
     int Index = (int)Objects.size()-NumFixedObjects-1;
+    MaxAlignment = std::max(MaxAlignment, Alignment);
     return Index;
   }