Index: lib/CodeGen/CGExpr.cpp
===================================================================
--- lib/CodeGen/CGExpr.cpp
+++ lib/CodeGen/CGExpr.cpp
@@ -1653,6 +1653,22 @@
return EmitLoadOfBitfieldLValue(LV, Loc);
}
+/// Check if current Field is better to be accessed separately. When current
+/// field has legal integer width, and its bitfield offset is naturally
+/// aligned, it is better to access the bitfield like a separate integer var.
+static bool IsSeparatableBitfield(const CGBitFieldInfo &Info,
+ const llvm::DataLayout &DL,
+ ASTContext &Context) {
+ if (!DL.isLegalInteger(Info.Size))
+ return false;
+ // Make sure Field is natually aligned.
+ if (Info.Offset %
+ (DL.getABIIntegerTypeAlignment(Info.Size) * Context.getCharWidth()) !=
+ 0)
+ return false;
+ return true;
+}
+
RValue CodeGenFunction::EmitLoadOfBitfieldLValue(LValue LV,
SourceLocation Loc) {
const CGBitFieldInfo &Info = LV.getBitFieldInfo();
@@ -1661,22 +1677,48 @@
llvm::Type *ResLTy = ConvertType(LV.getType());
Address Ptr = LV.getBitFieldAddress();
- llvm::Value *Val = Builder.CreateLoad(Ptr, LV.isVolatileQualified(), "bf.load");
-
- if (Info.IsSigned) {
- assert(static_cast<unsigned>(Info.Offset + Info.Size) <= Info.StorageSize);
- unsigned HighBits = Info.StorageSize - Info.Offset - Info.Size;
- if (HighBits)
- Val = Builder.CreateShl(Val, HighBits, "bf.shl");
- if (Info.Offset + HighBits)
- Val = Builder.CreateAShr(Val, Info.Offset + HighBits, "bf.ashr");
+ llvm::Value *Val = nullptr;
+ if (IsSeparatableBitfield(Info, CGM.getDataLayout(), getContext())) {
+ // Ptr is the pointer to the Bitfield Storage. Add Offset to the Ptr
+ // if the Offset is not zero.
+ if (Info.Offset != 0) {
+ Address BC = Builder.CreateBitCast(Ptr, Int8PtrTy);
+ llvm::Value *GEP = Builder.CreateGEP(
+ BC.getPointer(),
+ llvm::ConstantInt::get(Int32Ty,
+ Info.Offset / getContext().getCharWidth()));
+ Ptr = Address(GEP, Ptr.getAlignment());
+ }
+ // Adjust the element type of Ptr if it has different size with Info.Size.
+ if (Ptr.getElementType()->getScalarSizeInBits() != Info.Size) {
+ llvm::Type *BFType = llvm::Type::getIntNTy(getLLVMContext(), Info.Size);
+ llvm::Type *BFTypePtr =
+ llvm::Type::getIntNPtrTy(getLLVMContext(), Info.Size);
+ unsigned Align = CGM.getDataLayout().getABITypeAlignment(BFType) *
+ getContext().getCharWidth();
+ Ptr = Builder.CreateBitCast(
+ Address(Ptr.getPointer(), getContext().toCharUnitsFromBits(Align)),
+ BFTypePtr);
+ }
+ Val = Builder.CreateLoad(Ptr, LV.isVolatileQualified(), "bf.load");
} else {
- if (Info.Offset)
- Val = Builder.CreateLShr(Val, Info.Offset, "bf.lshr");
- if (static_cast<unsigned>(Info.Offset) + Info.Size < Info.StorageSize)
- Val = Builder.CreateAnd(Val, llvm::APInt::getLowBitsSet(Info.StorageSize,
- Info.Size),
- "bf.clear");
+ Val = Builder.CreateLoad(Ptr, LV.isVolatileQualified(), "bf.load");
+ if (Info.IsSigned) {
+ assert(static_cast<unsigned>(Info.Offset + Info.Size) <=
+ Info.StorageSize);
+ unsigned HighBits = Info.StorageSize - Info.Offset - Info.Size;
+ if (HighBits)
+ Val = Builder.CreateShl(Val, HighBits, "bf.shl");
+ if (Info.Offset + HighBits)
+ Val = Builder.CreateAShr(Val, Info.Offset + HighBits, "bf.ashr");
+ } else {
+ if (Info.Offset)
+ Val = Builder.CreateLShr(Val, Info.Offset, "bf.lshr");
+ if (static_cast<unsigned>(Info.Offset) + Info.Size < Info.StorageSize)
+ Val = Builder.CreateAnd(
+ Val, llvm::APInt::getLowBitsSet(Info.StorageSize, Info.Size),
+ "bf.clear");
+ }
}
Val = Builder.CreateIntCast(Val, ResLTy, Info.IsSigned, "bf.cast");
EmitScalarRangeCheck(Val, LV.getType(), Loc);
@@ -1866,15 +1908,43 @@
// Get the source value, truncated to the width of the bit-field.
llvm::Value *SrcVal = Src.getScalarVal();
+ llvm::Value *MaskedVal;
- // Cast the source to the storage type and shift it into place.
- SrcVal = Builder.CreateIntCast(SrcVal, Ptr.getElementType(),
- /*IsSigned=*/false);
- llvm::Value *MaskedVal = SrcVal;
-
- // See if there are other bits in the bitfield's storage we'll need to load
- // and mask together with source before storing.
- if (Info.StorageSize != Info.Size) {
+ bool SeparatableBitfield =
+ IsSeparatableBitfield(Info, CGM.getDataLayout(), getContext());
+ if (SeparatableBitfield) {
+ // Ptr is the pointer to the Bitfield Storage. Add Offset to the Ptr
+ // if the Offset is not zero.
+ if (Info.Offset != 0) {
+ Address BC = Builder.CreateBitCast(Ptr, Int8PtrTy);
+ llvm::Value *GEP = Builder.CreateGEP(
+ BC.getPointer(),
+ llvm::ConstantInt::get(Int32Ty,
+ Info.Offset / getContext().getCharWidth()));
+ Ptr = Address(GEP, Ptr.getAlignment());
+ }
+ // Adjust the element type of Ptr if it has different size with Info.Size.
+ if (Ptr.getElementType()->getScalarSizeInBits() != Info.Size) {
+ llvm::Type *BFType = llvm::Type::getIntNTy(getLLVMContext(), Info.Size);
+ llvm::Type *BFTypePtr =
+ llvm::Type::getIntNPtrTy(getLLVMContext(), Info.Size);
+ unsigned Align = CGM.getDataLayout().getABITypeAlignment(BFType) *
+ getContext().getCharWidth();
+ Ptr = Builder.CreateBitCast(
+ Address(Ptr.getPointer(), getContext().toCharUnitsFromBits(Align)),
+ BFTypePtr);
+ }
+ // Cast the source to the storage type and shift it into place.
+ SrcVal = Builder.CreateIntCast(SrcVal, Ptr.getElementType(),
+ /*IsSigned=*/false);
+ MaskedVal = SrcVal;
+ } else if (Info.StorageSize != Info.Size) {
+ // Cast the source to the storage type and shift it into place.
+ SrcVal = Builder.CreateIntCast(SrcVal, Ptr.getElementType(),
+ /*IsSigned=*/false);
+
+ // See if there are other bits in the bitfield's storage we'll need to load
+ // and mask together with source before storing.
assert(Info.StorageSize > Info.Size && "Invalid bitfield size.");
llvm::Value *Val =
Builder.CreateLoad(Ptr, Dst.isVolatileQualified(), "bf.load");
@@ -1900,6 +1970,10 @@
SrcVal = Builder.CreateOr(Val, SrcVal, "bf.set");
} else {
assert(Info.Offset == 0);
+ // Cast the source to the storage type and shift it into place.
+ SrcVal = Builder.CreateIntCast(SrcVal, Ptr.getElementType(),
+ /*IsSigned=*/false);
+ MaskedVal = SrcVal;
}
// Write the new value back out.
@@ -1910,7 +1984,7 @@
llvm::Value *ResultVal = MaskedVal;
// Sign extend the value if needed.
- if (Info.IsSigned) {
+ if (Info.IsSigned && !SeparatableBitfield) {
assert(Info.Size <= Info.StorageSize);
unsigned HighBits = Info.StorageSize - Info.Size;
if (HighBits) {
Index: test/CodeGen/2009-12-07-BitFieldAlignment.c
===================================================================
--- test/CodeGen/2009-12-07-BitFieldAlignment.c
+++ test/CodeGen/2009-12-07-BitFieldAlignment.c
@@ -4,7 +4,7 @@
struct S {
int a, b;
void *c;
- unsigned d : 8;
+ unsigned d : 7;
unsigned e : 8;
};