Change TargetData's algorithm for computing defualt vector type

alignment to match what's used in clang and GCC for __alignof, rather
than trying to guess what Legalize is going to be doing.

llvm-svn: 102206

1 files changed, 11 insertions, 16 deletions

diff --git a/llvm/lib/Target/TargetData.cpp b/llvm/lib/Target/TargetData.cpp
index d89fafd8137..5870d8a8700 100644
--- a/llvm/lib/Target/TargetData.cpp
+++ b/llvm/lib/Target/TargetData.cpp
@@ -269,18 +269,8 @@ unsigned TargetData::getAlignmentInfo(AlignTypeEnum AlignType,
       return ABIInfo ? Alignments[i].ABIAlign : Alignments[i].PrefAlign;
     
     // The best match so far depends on what we're looking for.
-    if (AlignType == VECTOR_ALIGN && Alignments[i].AlignType == VECTOR_ALIGN) {
-      // If this is a specification for a smaller vector type, we will fall back
-      // to it.  This happens because <128 x double> can be implemented in terms
-      // of 64 <2 x double>.
-      if (Alignments[i].TypeBitWidth < BitWidth) {
-        // Verify that we pick the biggest of the fallbacks.
-        if (BestMatchIdx == -1 ||
-            Alignments[BestMatchIdx].TypeBitWidth < Alignments[i].TypeBitWidth)
-          BestMatchIdx = i;
-      }
-    } else if (AlignType == INTEGER_ALIGN && 
-               Alignments[i].AlignType == INTEGER_ALIGN) {
+     if (AlignType == INTEGER_ALIGN && 
+         Alignments[i].AlignType == INTEGER_ALIGN) {
       // The "best match" for integers is the smallest size that is larger than
       // the BitWidth requested.
       if (Alignments[i].TypeBitWidth > BitWidth && (BestMatchIdx == -1 || 
@@ -303,10 +293,15 @@ unsigned TargetData::getAlignmentInfo(AlignTypeEnum AlignType,
     } else {
       assert(AlignType == VECTOR_ALIGN && "Unknown alignment type!");
 
-      // If we didn't find a vector size that is smaller or equal to this type,
-      // then we will end up scalarizing this to its element type.  Just return
-      // the alignment of the element.
-      return getAlignment(cast<VectorType>(Ty)->getElementType(), ABIInfo);
+      // By default, use natural alignment for vector types. This is consistent
+      // with what clang and llvm-gcc do.
+      unsigned Align = getTypeAllocSize(cast<VectorType>(Ty)->getElementType());
+      Align *= cast<VectorType>(Ty)->getNumElements();
+      // If the alignment is not a power of 2, round up to the next power of 2.
+      // This happens for non-power-of-2 length vectors.
+      if (Align & (Align-1))
+        Align = llvm::NextPowerOf2(Align);
+      return Align;
     }
   }