From 6e8fd9060253a29483ce628f6831786053516260 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Fri, 23 Apr 2010 19:41:15 +0000
Subject: [PATCH] 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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102206 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/TargetData.cpp        | 27 +++++++++++----------------
 test/CodeGen/X86/widen_load-2.ll |  6 +++---
 2 files changed, 14 insertions(+), 19 deletions(-)

diff --git a/lib/Target/TargetData.cpp b/lib/Target/TargetData.cpp
index d89fafd8137..5870d8a8700 100644
--- a/lib/Target/TargetData.cpp
+++ b/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;
     }
   }
 
diff --git a/test/CodeGen/X86/widen_load-2.ll b/test/CodeGen/X86/widen_load-2.ll
index 658c05143e8..551704c498f 100644
--- a/test/CodeGen/X86/widen_load-2.ll
+++ b/test/CodeGen/X86/widen_load-2.ll
@@ -24,10 +24,10 @@ define void @add3i32_2(%i32vec3*  sret %ret, %i32vec3* %ap, %i32vec3* %bp)  {
 ; CHECK: paddd
 ; CHECK: pextrd
 ; CHECK: movq
-	%a = load %i32vec3* %ap
-	%b = load %i32vec3* %bp
+	%a = load %i32vec3* %ap, align 8
+	%b = load %i32vec3* %bp, align 8
 	%x = add %i32vec3 %a, %b
-	store %i32vec3 %x, %i32vec3* %ret
+	store %i32vec3 %x, %i32vec3* %ret, align 8
 	ret void
 }
 
-- 
2.34.1