Make sure we correctly set the alignment for vector loads and stores associated with vector element lvalues. Patch by Kevin Schoedel (with some minor modifications by me).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@153285 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGExpr.cpp

@@ -950,9 +950,10 @@ RValue CodeGenFunction::EmitLoadOfLValue(LValue LV) {
   }
 
   if (LV.isVectorElt()) {
-    llvm::Value *Vec = Builder.CreateLoad(LV.getVectorAddr(),
-                                          LV.isVolatileQualified());
-    return RValue::get(Builder.CreateExtractElement(Vec, LV.getVectorIdx(),
+    llvm::LoadInst *Load = Builder.CreateLoad(LV.getVectorAddr(),
+                                              LV.isVolatileQualified());
+    Load->setAlignment(LV.getAlignment().getQuantity());
+    return RValue::get(Builder.CreateExtractElement(Load, LV.getVectorIdx(),
                                                     "vecext"));
   }
 
@@ -1039,8 +1040,10 @@ RValue CodeGenFunction::EmitLoadOfBitfieldLValue(LValue LV) {
 // If this is a reference to a subset of the elements of a vector, create an
 // appropriate shufflevector.
 RValue CodeGenFunction::EmitLoadOfExtVectorElementLValue(LValue LV) {
-  llvm::Value *Vec = Builder.CreateLoad(LV.getExtVectorAddr(),
-                                        LV.isVolatileQualified());
+  llvm::LoadInst *Load = Builder.CreateLoad(LV.getExtVectorAddr(),
+                                            LV.isVolatileQualified());
+  Load->setAlignment(LV.getAlignment().getQuantity());
+  llvm::Value *Vec = Load;
 
   const llvm::Constant *Elts = LV.getExtVectorElts();
 
@@ -1075,11 +1078,15 @@ void CodeGenFunction::EmitStoreThroughLValue(RValue Src, LValue Dst, bool isInit
   if (!Dst.isSimple()) {
     if (Dst.isVectorElt()) {
       // Read/modify/write the vector, inserting the new element.
-      llvm::Value *Vec = Builder.CreateLoad(Dst.getVectorAddr(),
-                                            Dst.isVolatileQualified());
+      llvm::LoadInst *Load = Builder.CreateLoad(Dst.getVectorAddr(),
+                                                Dst.isVolatileQualified());
+      Load->setAlignment(Dst.getAlignment().getQuantity());
+      llvm::Value *Vec = Load;
       Vec = Builder.CreateInsertElement(Vec, Src.getScalarVal(),
                                         Dst.getVectorIdx(), "vecins");
-      Builder.CreateStore(Vec, Dst.getVectorAddr(),Dst.isVolatileQualified());
+      llvm::StoreInst *Store = Builder.CreateStore(Vec, Dst.getVectorAddr(),
+                                                   Dst.isVolatileQualified());
+      Store->setAlignment(Dst.getAlignment().getQuantity());
       return;
     }
 
@@ -1263,8 +1270,10 @@ void CodeGenFunction::EmitStoreThroughExtVectorComponentLValue(RValue Src,
                                                                LValue Dst) {
   // This access turns into a read/modify/write of the vector.  Load the input
   // value now.
-  llvm::Value *Vec = Builder.CreateLoad(Dst.getExtVectorAddr(),
-                                        Dst.isVolatileQualified());
+  llvm::LoadInst *Load = Builder.CreateLoad(Dst.getExtVectorAddr(),
+                                            Dst.isVolatileQualified());
+  Load->setAlignment(Dst.getAlignment().getQuantity());
+  llvm::Value *Vec = Load;
   const llvm::Constant *Elts = Dst.getExtVectorElts();
 
   llvm::Value *SrcVal = Src.getScalarVal();
@@ -1320,7 +1329,9 @@ void CodeGenFunction::EmitStoreThroughExtVectorComponentLValue(RValue Src,
     Vec = Builder.CreateInsertElement(Vec, SrcVal, Elt);
   }
 
-  Builder.CreateStore(Vec, Dst.getExtVectorAddr(), Dst.isVolatileQualified());
+  llvm::StoreInst *Store = Builder.CreateStore(Vec, Dst.getExtVectorAddr(),
+                                               Dst.isVolatileQualified());
+  Store->setAlignment(Dst.getAlignment().getQuantity());
 }
 
 // setObjCGCLValueClass - sets class of he lvalue for the purpose of
@@ -1722,7 +1733,7 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E) {
     assert(LHS.isSimple() && "Can only subscript lvalue vectors here!");
     Idx = Builder.CreateIntCast(Idx, Int32Ty, IdxSigned, "vidx");
     return LValue::MakeVectorElt(LHS.getAddress(), Idx,
-                                 E->getBase()->getType());
+                                 E->getBase()->getType(), LHS.getAlignment());
   }
 
   // Extend or truncate the index type to 32 or 64-bits.
@@ -1888,7 +1899,8 @@ EmitExtVectorElementExpr(const ExtVectorElementExpr *E) {
 
   if (Base.isSimple()) {
     llvm::Constant *CV = GenerateConstantVector(Builder, Indices);
-    return LValue::MakeExtVectorElt(Base.getAddress(), CV, type);
+    return LValue::MakeExtVectorElt(Base.getAddress(), CV, type,
+                                    Base.getAlignment());
   }
   assert(Base.isExtVectorElt() && "Can only subscript lvalue vec elts here!");
 
@@ -1898,7 +1910,8 @@ EmitExtVectorElementExpr(const ExtVectorElementExpr *E) {
   for (unsigned i = 0, e = Indices.size(); i != e; ++i)
     CElts.push_back(BaseElts->getAggregateElement(Indices[i]));
   llvm::Constant *CV = llvm::ConstantVector::get(CElts);
-  return LValue::MakeExtVectorElt(Base.getExtVectorAddr(), CV, type);
+  return LValue::MakeExtVectorElt(Base.getExtVectorAddr(), CV, type,
+                                  Base.getAlignment());
 }
 
 LValue CodeGenFunction::EmitMemberExpr(const MemberExpr *E) {

lib/CodeGen/CGValue.h

@@ -126,7 +126,8 @@ class LValue {
   // 'const' is unused here
   Qualifiers Quals;
 
-  /// The alignment to use when accessing this lvalue.
+  // The alignment to use when accessing this lvalue.  (For vector elements,
+  // this is the alignment of the whole vector.)
   unsigned short Alignment;
 
   // objective-c's ivar
@@ -267,22 +268,22 @@ public:
   }
 
   static LValue MakeVectorElt(llvm::Value *Vec, llvm::Value *Idx,
-                              QualType type) {
+                              QualType type, CharUnits Alignment) {
     LValue R;
     R.LVType = VectorElt;
     R.V = Vec;
     R.VectorIdx = Idx;
-    R.Initialize(type, type.getQualifiers());
+    R.Initialize(type, type.getQualifiers(), Alignment);
     return R;
   }
 
   static LValue MakeExtVectorElt(llvm::Value *Vec, llvm::Constant *Elts,
-                                 QualType type) {
+                                 QualType type, CharUnits Alignment) {
     LValue R;
     R.LVType = ExtVectorElt;
     R.V = Vec;
     R.VectorElts = Elts;
-    R.Initialize(type, type.getQualifiers());
+    R.Initialize(type, type.getQualifiers(), Alignment);
     return R;
   }
 

test/CodeGen/ext-vector-member-alignment.c

@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck %s
+
+typedef float float4 __attribute__((ext_vector_type(4)));
+
+struct __attribute__((packed, aligned(4))) struct1 {
+  float4 position;
+};
+int x = __alignof(struct struct1);
+
+float4 f(struct struct1* x) { return x->position; }
+
+void func(struct struct1* p, float *a, float *b, float c) {
+  p->position.x = c;
+  *a = p->position.y;
+  *b = p->position[0];
+  p->position[2] = c;
+  // FIXME: We should be able to come up with a more aggressive alignment
+  // estimate.
+  // CHECK: @func
+  // CHECK: load <4 x float>* {{%.*}}, align 1
+  // CHECK: store <4 x float> {{%.*}}, <4 x float>* {{%.*}}, align 1
+  // CHECK: load <4 x float>* {{%.*}}, align 1
+  // CHECK: load <4 x float>* {{%.*}}, align 1
+  // CHECK: load <4 x float>* {{%.*}}, align 1
+  // CHECK: store <4 x float> {{%.*}}, <4 x float>* {{%.*}}, align 1
+  // CHECK: ret void
+}