Fix va_arg for doubles. With this patch VAARG nodes always contain the

correct alignment information, which simplifies ExpandRes_VAARG a bit.

The patch introduces a new alignment information to TargetLoweringInfo. This is
needed since the two natural candidates cannot be used:

* The 's' in target data: If this is set to the minimal alignment of any
  argument, getCallFrameTypeAlignment would return 4 for doubles on ARM for
  example.
* The getTransientStackAlignment method. It is possible for an architecture to
  have argument less aligned than what we maintain the stack pointer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108072 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/SelectionDAG.h

@@ -582,7 +582,7 @@ public:
   /// getVAArg - VAArg produces a result and token chain, and takes a pointer
   /// and a source value as input.
   SDValue getVAArg(EVT VT, DebugLoc dl, SDValue Chain, SDValue Ptr,
-                   SDValue SV, unsigned Align = 0);
+                   SDValue SV, unsigned Align);
 
   /// getAtomic - Gets a node for an atomic op, produces result and chain and
   /// takes 3 operands

include/llvm/Target/TargetLowering.h

@@ -686,6 +686,12 @@ public:
     return JumpBufAlignment;
   }
 
+  /// getMinStackArgumentAlignment - return the minimum stack alignment of an
+  /// argument.
+  unsigned getMinStackArgumentAlignment() const {
+    return MinStackArgumentAlignment;
+  }
+
   /// getPrefLoopAlignment - return the preferred loop alignment.
   ///
   unsigned getPrefLoopAlignment() const {
@@ -1082,6 +1088,12 @@ protected:
     PrefLoopAlignment = Align;
   }
 
+  /// setMinStackArgumentAlignment - Set the minimum stack alignment of an
+  /// argument.
+  void setMinStackArgumentAlignment(unsigned Align) {
+    MinStackArgumentAlignment = Align;
+  }
+
   /// setShouldFoldAtomicFences - Set if the target's implementation of the
   /// atomic operation intrinsics includes locking. Default is false.
   void setShouldFoldAtomicFences(bool fold) {
@@ -1515,6 +1527,11 @@ private:
   /// buffers
   unsigned JumpBufAlignment;
 
+  /// MinStackArgumentAlignment - The minimum alginment that any argument
+  /// on the stack needs to have.
+  ///
+  unsigned MinStackArgumentAlignment;
+
   /// PrefLoopAlignment - The perferred loop alignment.
   ///
   unsigned PrefLoopAlignment;