Executive summary: getTypeSize -> getTypeStoreSize / getABITypeSize.

The meaning of getTypeSize was not clear - clarifying it is important
now that we have x86 long double and arbitrary precision integers.
The issue with long double is that it requires 80 bits, and this is
not a multiple of its alignment.  This gives a primitive type for
which getTypeSize differed from getABITypeSize.  For arbitrary precision
integers it is even worse: there is the minimum number of bits needed to
hold the type (eg: 36 for an i36), the maximum number of bits that will
be overwriten when storing the type (40 bits for i36) and the ABI size
(i.e. the storage size rounded up to a multiple of the alignment; 64 bits
for i36).

This patch removes getTypeSize (not really - it is still there but
deprecated to allow for a gradual transition).  Instead there is:

(1) getTypeSizeInBits - a number of bits that suffices to hold all
values of the type.  For a primitive type, this is the minimum number
of bits.  For an i36 this is 36 bits.  For x86 long double it is 80.
This corresponds to gcc's TYPE_PRECISION.

(2) getTypeStoreSizeInBits - the maximum number of bits that is
written when storing the type (or read when reading it).  For an
i36 this is 40 bits, for an x86 long double it is 80 bits.  This
is the size alias analysis is interested in (getTypeStoreSize
returns the number of bytes).  There doesn't seem to be anything
corresponding to this in gcc.

(3) getABITypeSizeInBits - this is getTypeStoreSizeInBits rounded
up to a multiple of the alignment.  For an i36 this is 64, for an
x86 long double this is 96 or 128 depending on the OS.  This is the
spacing between consecutive elements when you form an array out of
this type (getABITypeSize returns the number of bytes).  This is
TYPE_SIZE in gcc.

Since successive elements in a SequentialType (arrays, pointers
and vectors) need to be aligned, the spacing between them will be
given by getABITypeSize.  This means that the size of an array
is the length times the getABITypeSize.  It also means that GEP
computations need to use getABITypeSize when computing offsets.
Furthermore, if an alloca allocates several elements at once then
these too need to be aligned, so the size of the alloca has to be
the number of elements multiplied by getABITypeSize.  Logically
speaking this doesn't have to be the case when allocating just
one element, but it is simpler to also use getABITypeSize in this
case.  So alloca's and mallocs should use getABITypeSize.  Finally,
since gcc's only notion of size is that given by getABITypeSize, if
you want to output assembler etc the same as gcc then getABITypeSize
is the size you want.

Since a store will overwrite no more than getTypeStoreSize bytes,
and a read will read no more than that many bytes, this is the
notion of size appropriate for alias analysis calculations.

In this patch I have corrected all type size uses except some of
those in ScalarReplAggregates, lib/Codegen, lib/Target (the hard
cases).  I will get around to auditing these too at some point,
but I could do with some help.

Finally, I made one change which I think wise but others might
consider pointless and suboptimal: in an unpacked struct the
amount of space allocated for a field is now given by the ABI
size rather than getTypeStoreSize.  I did this because every
other place that reserves memory for a type (eg: alloca) now
uses getABITypeSize, and I didn't want to make an exception
for unpacked structs, i.e. I did it to make things more uniform.
This only effects structs containing long doubles and arbitrary
precision integers.  If someone wants to pack these types more
tightly they can always use a packed struct.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43620 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 23 insertions, 60 deletions

diff --git a/lib/Target/TargetData.cpp b/lib/Target/TargetData.cpp
index b1b78a8ada..5a189205ed 100644
--- a/lib/Target/TargetData.cpp
+++ b/lib/Target/TargetData.cpp
@@ -49,14 +49,13 @@ StructLayout::StructLayout(const StructType *ST, const TargetData &TD) {
   // Loop over each of the elements, placing them in memory...
   for (unsigned i = 0, e = NumElements; i != e; ++i) {
     const Type *Ty = ST->getElementType(i);
-    unsigned TyAlign;
-    uint64_t TySize;
-    TyAlign = (ST->isPacked() ? 1 : TD.getABITypeAlignment(Ty));
-    TySize = TD.getTypeSize(Ty);
+    unsigned TyAlign = ST->isPacked() ?
+      1 : TD.getABITypeAlignment(Ty);
+    uint64_t TySize  = ST->isPacked() ?
+      TD.getTypeStoreSize(Ty) : TD.getABITypeSize(Ty);
 
-    // Add padding if necessary to make the data element aligned properly...
-    if (StructSize % TyAlign != 0)
-      StructSize = (StructSize/TyAlign + 1) * TyAlign;   // Add padding...
+    // Add padding if necessary to align the data element properly...
+    StructSize = (StructSize + TyAlign - 1)/TyAlign * TyAlign;
 
     // Keep track of maximum alignment constraint
     StructAlignment = std::max(TyAlign, StructAlignment);
@@ -406,83 +405,47 @@ std::string TargetData::getStringRepresentation() const {
 }
 
 
-uint64_t TargetData::getTypeSize(const Type *Ty) const {
+uint64_t TargetData::getTypeSizeInBits(const Type *Ty) const {
   assert(Ty->isSized() && "Cannot getTypeInfo() on a type that is unsized!");
   switch (Ty->getTypeID()) {
   case Type::LabelTyID:
   case Type::PointerTyID:
-    return getPointerSize();
+    return getPointerSizeInBits();
   case Type::ArrayTyID: {
     const ArrayType *ATy = cast<ArrayType>(Ty);
-    uint64_t Size;
-    unsigned char Alignment;
-    Size = getTypeSize(ATy->getElementType());
-    Alignment = getABITypeAlignment(ATy->getElementType());
-    uint64_t AlignedSize = (Size + Alignment - 1)/Alignment*Alignment;
-    return AlignedSize*ATy->getNumElements();
+    return getABITypeSizeInBits(ATy->getElementType())*ATy->getNumElements();
   }
   case Type::StructTyID: {
     // Get the layout annotation... which is lazily created on demand.
     const StructLayout *Layout = getStructLayout(cast<StructType>(Ty));
-    return Layout->getSizeInBytes();
-  }
-  case Type::IntegerTyID: {
-    unsigned BitWidth = cast<IntegerType>(Ty)->getBitWidth();
-    if (BitWidth <= 8) {
-      return 1;
-    } else if (BitWidth <= 16) {
-      return 2;
-    } else if (BitWidth <= 32) {
-      return 4;
-    } else if (BitWidth <= 64) {
-      return 8;
-    } else {
-      // The size of this > 64 bit type is chosen as a multiple of the
-      // preferred alignment of the largest "native" size the target supports. 
-      // We first obtain the the alignment info for this type and then compute
-      // the next largest multiple of that size.
-      uint64_t size = getAlignmentInfo(INTEGER_ALIGN, BitWidth, false) * 8;
-      return (((BitWidth / (size)) + (BitWidth % size != 0)) * size) / 8;
-    }
-    break;
+    return Layout->getSizeInBits();
   }
+  case Type::IntegerTyID:
+    return cast<IntegerType>(Ty)->getBitWidth();
   case Type::VoidTyID:
-    return 1;
+    return 8;
   case Type::FloatTyID:
-    return 4;
+    return 32;
   case Type::DoubleTyID:
-    return 8;
+    return 64;
   case Type::PPC_FP128TyID:
   case Type::FP128TyID:
-    return 16;
+    return 128;
   // In memory objects this is always aligned to a higher boundary, but
-  // only 10 bytes contain information.
+  // only 80 bits contain information.
   case Type::X86_FP80TyID:
-    return 10;
+    return 80;
   case Type::VectorTyID: {
     const VectorType *PTy = cast<VectorType>(Ty);
-    return PTy->getBitWidth() / 8;
+    return PTy->getBitWidth();
   }
   default:
-    assert(0 && "TargetData::getTypeSize(): Unsupported type");
+    assert(0 && "TargetData::getTypeSizeInBits(): Unsupported type");
     break;
   }
   return 0;
 }
 
-uint64_t TargetData::getTypeSizeInBits(const Type *Ty) const {
-  if (Ty->isInteger())
-    return cast<IntegerType>(Ty)->getBitWidth();
-  else
-    return getTypeSize(Ty) * 8;
-}
-
-uint64_t TargetData::getABITypeSizeInBits(const Type *Ty) const {
-  if (Ty->isInteger())
-    return cast<IntegerType>(Ty)->getBitWidth();
-  else
-    return getABITypeSize(Ty) * 8;
-}
 /*!
   \param abi_or_pref Flag that determines which alignment is returned. true
   returns the ABI alignment, false returns the preferred alignment.
@@ -542,7 +505,7 @@ unsigned char TargetData::getAlignment(const Type *Ty, bool abi_or_pref) const {
     break;
   }
 
-  return getAlignmentInfo((AlignTypeEnum)AlignType, getTypeSize(Ty) * 8,
+  return getAlignmentInfo((AlignTypeEnum)AlignType, getTypeSizeInBits(Ty),
                           abi_or_pref);
 }
 
@@ -603,7 +566,7 @@ uint64_t TargetData::getIndexedOffset(const Type *ptrTy, Value* const* Indices,
 
       // Get the array index and the size of each array element.
       int64_t arrayIdx = cast<ConstantInt>(Indices[CurIDX])->getSExtValue();
-      Result += arrayIdx * (int64_t)getTypeSize(Ty);
+      Result += arrayIdx * (int64_t)getABITypeSize(Ty);
     }
   }
 
@@ -623,7 +586,7 @@ unsigned TargetData::getPreferredAlignmentLog(const GlobalVariable *GV) const {
     if (Alignment < 4) {
       // If the global is not external, see if it is large.  If so, give it a
       // larger alignment.
-      if (getTypeSize(ElemType) > 128)
+      if (getTypeSizeInBits(ElemType) > 128)
         Alignment = 4;    // 16-byte alignment.
     }
   }