Add a per target max vector alignment field (e.g., 32-byte alignment for x86 due to

AVX).  Currently, if no aligned attribute is specified the alignment of a vector is
inferred from its size.  Thus, very large vectors will be over-aligned with no 
benefit.  Target owners should set this target max.

llvm-svn: 160209

3 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index a9681d86697..b0351d69adb 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -1047,6 +1047,10 @@ ASTContext::getTypeInfoImpl(const Type *T) const {
       Align = llvm::NextPowerOf2(Align);
       Width = llvm::RoundUpToAlignment(Width, Align);
     }
+    // Adjust the alignment based on the target max.
+    uint64_t TargetVectorAlign = Target->getMaxVectorAlign();
+    if (TargetVectorAlign && TargetVectorAlign < Align)
+      Align = TargetVectorAlign;
     break;
   }
 
diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index 8c49486b0dc..db5941a5d92 100644
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -47,6 +47,7 @@ TargetInfo::TargetInfo(const std::string &T) : Triple(T) {
   LargeArrayMinWidth = 0;
   LargeArrayAlign = 0;
   MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 0;
+  MaxVectorAlign = 0;
   SizeType = UnsignedLong;
   PtrDiffType = SignedLong;
   IntMaxType = SignedLongLong;
diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 3df59c35d12..193241361da 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -2448,6 +2448,7 @@ public:
     LongDoubleWidth = 128;
     LongDoubleAlign = 128;
     SuitableAlign = 128;
+    MaxVectorAlign = 256;
     SizeType = UnsignedLong;
     IntPtrType = SignedLong;
     DescriptionString = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-"
@@ -2755,6 +2756,7 @@ public:
   DarwinX86_64TargetInfo(const std::string& triple)
       : DarwinTargetInfo<X86_64TargetInfo>(triple) {
     Int64Type = SignedLongLong;
+    MaxVectorAlign = 256;
   }
 };
 } // end anonymous namespace