Propagate lvalue alignment into bitfields. Per report on cfe-dev.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@159295 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index c8563d6044e7ee8653b70a8f406e76646fb2ef79..cb446dfeb4ab44d440b316537a9bb5cf7ddb665d 100644 (file)
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1047,6 +1047,9 @@ RValue CodeGenFunction::EmitLoadOfBitfieldLValue(LValue LV) {
   llvm::Value *Res = 0;
   for (unsigned i = 0, e = Info.getNumComponents(); i != e; ++i) {
     const CGBitFieldInfo::AccessInfo &AI = Info.getComponent(i);
+    CharUnits AccessAlignment = AI.AccessAlignment;
+    if (!LV.getAlignment().isZero())
+      AccessAlignment = std::min(AccessAlignment, LV.getAlignment());
 
     // Get the field pointer.
     llvm::Value *Ptr = LV.getBitFieldBaseAddr();
@@ -1070,8 +1073,7 @@ RValue CodeGenFunction::EmitLoadOfBitfieldLValue(LValue LV) {
 
     // Perform the load.
     llvm::LoadInst *Load = Builder.CreateLoad(Ptr, LV.isVolatileQualified());
-    if (!AI.AccessAlignment.isZero())
-      Load->setAlignment(AI.AccessAlignment.getQuantity());
+    Load->setAlignment(AccessAlignment.getQuantity());
 
     // Shift out unused low bits and mask out unused high bits.
     llvm::Value *Val = Load;
@@ -1270,6 +1272,9 @@ void CodeGenFunction::EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst,
   // Iterate over the components, writing each piece to memory.
   for (unsigned i = 0, e = Info.getNumComponents(); i != e; ++i) {
     const CGBitFieldInfo::AccessInfo &AI = Info.getComponent(i);
+    CharUnits AccessAlignment = AI.AccessAlignment;
+    if (!Dst.getAlignment().isZero())
+      AccessAlignment = std::min(AccessAlignment, Dst.getAlignment());
 
     // Get the field pointer.
     llvm::Value *Ptr = Dst.getBitFieldBaseAddr();
@@ -1316,8 +1321,7 @@ void CodeGenFunction::EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst,
     // If necessary, load and OR in bits that are outside of the bit-field.
     if (AI.TargetBitWidth != AI.AccessWidth) {
       llvm::LoadInst *Load = Builder.CreateLoad(Ptr, Dst.isVolatileQualified());
-      if (!AI.AccessAlignment.isZero())
-        Load->setAlignment(AI.AccessAlignment.getQuantity());
+      Load->setAlignment(AccessAlignment.getQuantity());
 
       // Compute the mask for zeroing the bits that are part of the bit-field.
       llvm::APInt InvMask =
@@ -1331,8 +1335,7 @@ void CodeGenFunction::EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst,
     // Write the value.
     llvm::StoreInst *Store = Builder.CreateStore(Val, Ptr,
                                                  Dst.isVolatileQualified());
-    if (!AI.AccessAlignment.isZero())
-      Store->setAlignment(AI.AccessAlignment.getQuantity());
+    Store->setAlignment(AccessAlignment.getQuantity());
   }
 }
 
@@ -2084,16 +2087,6 @@ LValue CodeGenFunction::EmitMemberExpr(const MemberExpr *E) {
   llvm_unreachable("Unhandled member declaration!");
 }
 
-LValue CodeGenFunction::EmitLValueForBitfield(llvm::Value *BaseValue,
-                                              const FieldDecl *Field,
-                                              unsigned CVRQualifiers) {
-  const CGRecordLayout &RL =
-    CGM.getTypes().getCGRecordLayout(Field->getParent());
-  const CGBitFieldInfo &Info = RL.getBitFieldInfo(Field);
-  return LValue::MakeBitfield(BaseValue, Info,
-                          Field->getType().withCVRQualifiers(CVRQualifiers));
-}
-
 /// EmitLValueForAnonRecordField - Given that the field is a member of
 /// an anonymous struct or union buried inside a record, and given
 /// that the base value is a pointer to the enclosing record, derive
@@ -2118,9 +2111,15 @@ LValue CodeGenFunction::EmitLValueForAnonRecordField(llvm::Value *BaseValue,
 
 LValue CodeGenFunction::EmitLValueForField(LValue base,
                                            const FieldDecl *field) {
-  if (field->isBitField())
-    return EmitLValueForBitfield(base.getAddress(), field,
-                                 base.getVRQualifiers());
+  if (field->isBitField()) {
+    const CGRecordLayout &RL =
+      CGM.getTypes().getCGRecordLayout(field->getParent());
+    const CGBitFieldInfo &Info = RL.getBitFieldInfo(field);
+    QualType fieldType =
+      field->getType().withCVRQualifiers(base.getVRQualifiers());
+    return LValue::MakeBitfield(base.getAddress(), Info, fieldType,
+                                base.getAlignment());
+  }
 
   const RecordDecl *rec = field->getParent();
   QualType type = field->getType();

diff --git a/lib/CodeGen/CGObjCRuntime.cpp b/lib/CodeGen/CGObjCRuntime.cpp
index 0f5cbc19d6b225f610f69c33e46ade3a9bde8d32..7cf0ed236f22f69c78609c6bba066e92751c2fa2 100644 (file)
--- a/lib/CodeGen/CGObjCRuntime.cpp
+++ b/lib/CodeGen/CGObjCRuntime.cpp
@@ -120,6 +120,8 @@ LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
   uint64_t ContainingTypeAlign = CGF.CGM.getContext().getTargetInfo().getCharAlign();
   uint64_t ContainingTypeSize = TypeSizeInBits - (FieldBitOffset - BitOffset);
   uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext());
+  CharUnits ContainingTypeAlignCharUnits = 
+    CGF.CGM.getContext().toCharUnitsFromBits(ContainingTypeAlign);
 
   // Allocate a new CGBitFieldInfo object to describe this access.
   //
@@ -132,7 +134,8 @@ LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
                              ContainingTypeSize, ContainingTypeAlign));
 
   return LValue::MakeBitfield(V, *Info,
-                              IvarTy.withCVRQualifiers(CVRQualifiers));
+                              IvarTy.withCVRQualifiers(CVRQualifiers),
+                              ContainingTypeAlignCharUnits);
 }
 
 namespace {

diff --git a/lib/CodeGen/CGRecordLayout.h b/lib/CodeGen/CGRecordLayout.h
index 25a0a508f188f3d66051b68db568e6527fb2abd3..94c822f49f1725d3276082085906c21e36d7e54e 100644 (file)
--- a/lib/CodeGen/CGRecordLayout.h
+++ b/lib/CodeGen/CGRecordLayout.h
@@ -64,12 +64,7 @@ public:
     /// Bit width of the memory access to perform.
     unsigned AccessWidth;
 
-    /// The alignment of the memory access, or 0 if the default alignment should
-    /// be used.
-    //
-    // FIXME: Remove use of 0 to encode default, instead have IRgen do the right
-    // thing when it generates the code, if avoiding align directives is
-    // desired.
+    /// The alignment of the memory access, assuming the parent is aligned.
     CharUnits AccessAlignment;
 
     /// Offset for the target value.

diff --git a/lib/CodeGen/CGRecordLayoutBuilder.cpp b/lib/CodeGen/CGRecordLayoutBuilder.cpp
index 382cbfd10def92ba3784a67389b8370196f1c715..d642ef8533c57cde465428bc4b500e120ad4e099 100644 (file)
--- a/lib/CodeGen/CGRecordLayoutBuilder.cpp
+++ b/lib/CodeGen/CGRecordLayoutBuilder.cpp
@@ -235,6 +235,8 @@ CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
                                uint64_t FieldSize,
                                uint64_t ContainingTypeSizeInBits,
                                unsigned ContainingTypeAlign) {
+  assert(ContainingTypeAlign && "Expected alignment to be specified");
+
   llvm::Type *Ty = Types.ConvertTypeForMem(FD->getType());
   CharUnits TypeSizeInBytes =
     CharUnits::fromQuantity(Types.getTargetData().getTypeAllocSize(Ty));

diff --git a/lib/CodeGen/CGValue.h b/lib/CodeGen/CGValue.h
index ac704e7dca40c37ab40afbdf1f61445d3eb56030..dd9208f91386aece8668b2ee126931a35a0c3474 100644 (file)
--- a/lib/CodeGen/CGValue.h
+++ b/lib/CodeGen/CGValue.h
@@ -153,7 +153,7 @@ class LValue {
 
 private:
   void Initialize(QualType Type, Qualifiers Quals,
-                  CharUnits Alignment = CharUnits(),
+                  CharUnits Alignment,
                   llvm::MDNode *TBAAInfo = 0) {
     this->Type = Type;
     this->Quals = Quals;
@@ -295,12 +295,12 @@ public:
   /// access.
   static LValue MakeBitfield(llvm::Value *BaseValue,
                              const CGBitFieldInfo &Info,
-                             QualType type) {
+                             QualType type, CharUnits Alignment) {
     LValue R;
     R.LVType = BitField;
     R.V = BaseValue;
     R.BitFieldInfo = &Info;
-    R.Initialize(type, type.getQualifiers());
+    R.Initialize(type, type.getQualifiers(), Alignment);
     return R;
   }
 

diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index b26d174180a60f319d5ca487646310dc433ec003..fd93fbbdd2095c5ce4bb179c191b9bcab4054fc5 100644 (file)
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -2166,9 +2166,6 @@ public:
                            llvm::Value* Base, const ObjCIvarDecl *Ivar,
                            unsigned CVRQualifiers);
 
-  LValue EmitLValueForBitfield(llvm::Value* Base, const FieldDecl* Field,
-                                unsigned CVRQualifiers);
-
   LValue EmitCXXConstructLValue(const CXXConstructExpr *E);
   LValue EmitCXXBindTemporaryLValue(const CXXBindTemporaryExpr *E);
   LValue EmitLambdaLValue(const LambdaExpr *E);

diff --git a/test/CodeGen/packed-nest-unpacked.c b/test/CodeGen/packed-nest-unpacked.c
index 0ccc0c41b7e601d3c317f8c26c4a47ee8e9cdda2..6097e3f32eae725a8fa2fee70d885cac21ccc47a 100644 (file)
--- a/test/CodeGen/packed-nest-unpacked.c
+++ b/test/CodeGen/packed-nest-unpacked.c
@@ -45,3 +45,21 @@ void test6() {
   // CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* bitcast (%struct.X* getelementptr inbounds (%struct.Y* @g, i32 0, i32 1) to i8*), i8* %{{.*}}, i64 24, i32 1, i1 false)
   g.y = foo();
 }
+
+
+struct XBitfield {
+  unsigned b1 : 10;
+  unsigned b2 : 12;
+  unsigned b3 : 10;
+};
+struct YBitfield {
+  char x;
+  struct XBitfield y;
+} __attribute((packed));
+struct YBitfield gbitfield;
+
+unsigned test7() {
+  // CHECK: @test7
+  // CHECK: load i32* bitcast (%struct.XBitfield* getelementptr inbounds (%struct.YBitfield* @gbitfield, i32 0, i32 1) to i32*), align 1
+  return gbitfield.y.b2;
+}