diff options
Diffstat (limited to 'clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp')
| -rw-r--r-- | clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp | 247 |
1 files changed, 240 insertions, 7 deletions
diff --git a/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp b/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp index e20a4fc..59aa257 100644 --- a/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp +++ b/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp @@ -118,6 +118,9 @@ class ConstantAggregateBuilder : private ConstantAggregateBuilderUtils { /// non-packed LLVM struct will give the correct layout. bool naturalLayout = true; + bool split(size_t index, CharUnits hint); + std::optional<size_t> splitAt(CharUnits pos); + static mlir::Attribute buildFrom(CIRGenModule &cgm, ArrayRef<Element> elems, CharUnits startOffset, CharUnits size, bool naturalLayout, mlir::Type desiredTy, @@ -137,6 +140,10 @@ public: /// Update or overwrite the bits starting at \p offsetInBits with \p bits. bool addBits(llvm::APInt bits, uint64_t offsetInBits, bool allowOverwrite); + /// Attempt to condense the value starting at \p offset to a constant of type + /// \p desiredTy. + void condense(CharUnits offset, mlir::Type desiredTy); + /// Produce a constant representing the entire accumulated value, ideally of /// the specified type. If \p allowOversized, the constant might be larger /// than implied by \p desiredTy (eg, if there is a flexible array member). @@ -176,6 +183,195 @@ bool ConstantAggregateBuilder::add(mlir::TypedAttr typedAttr, CharUnits offset, return false; } +bool ConstantAggregateBuilder::addBits(llvm::APInt bits, uint64_t offsetInBits, + bool allowOverwrite) { + const ASTContext &astContext = cgm.getASTContext(); + const uint64_t charWidth = astContext.getCharWidth(); + mlir::Type charTy = cgm.getBuilder().getUIntNTy(charWidth); + + // Offset of where we want the first bit to go within the bits of the + // current char. + unsigned offsetWithinChar = offsetInBits % charWidth; + + // We split bit-fields up into individual bytes. Walk over the bytes and + // update them. + for (CharUnits offsetInChars = + astContext.toCharUnitsFromBits(offsetInBits - offsetWithinChar); + /**/; ++offsetInChars) { + // Number of bits we want to fill in this char. + unsigned wantedBits = + std::min((uint64_t)bits.getBitWidth(), charWidth - offsetWithinChar); + + // Get a char containing the bits we want in the right places. The other + // bits have unspecified values. + llvm::APInt bitsThisChar = bits; + if (bitsThisChar.getBitWidth() < charWidth) + bitsThisChar = bitsThisChar.zext(charWidth); + if (cgm.getDataLayout().isBigEndian()) { + // Figure out how much to shift by. We may need to left-shift if we have + // less than one byte of Bits left. + int shift = bits.getBitWidth() - charWidth + offsetWithinChar; + if (shift > 0) + bitsThisChar.lshrInPlace(shift); + else if (shift < 0) + bitsThisChar = bitsThisChar.shl(-shift); + } else { + bitsThisChar = bitsThisChar.shl(offsetWithinChar); + } + if (bitsThisChar.getBitWidth() > charWidth) + bitsThisChar = bitsThisChar.trunc(charWidth); + + if (wantedBits == charWidth) { + // Got a full byte: just add it directly. + add(cir::IntAttr::get(charTy, bitsThisChar), offsetInChars, + allowOverwrite); + } else { + // Partial byte: update the existing integer if there is one. If we + // can't split out a 1-CharUnit range to update, then we can't add + // these bits and fail the entire constant emission. + std::optional<size_t> firstElemToUpdate = splitAt(offsetInChars); + if (!firstElemToUpdate) + return false; + std::optional<size_t> lastElemToUpdate = + splitAt(offsetInChars + CharUnits::One()); + if (!lastElemToUpdate) + return false; + assert(*lastElemToUpdate - *firstElemToUpdate < 2 && + "should have at most one element covering one byte"); + + // Figure out which bits we want and discard the rest. + llvm::APInt updateMask(charWidth, 0); + if (cgm.getDataLayout().isBigEndian()) + updateMask.setBits(charWidth - offsetWithinChar - wantedBits, + charWidth - offsetWithinChar); + else + updateMask.setBits(offsetWithinChar, offsetWithinChar + wantedBits); + bitsThisChar &= updateMask; + bool isNull = false; + if (*firstElemToUpdate < elements.size()) { + auto firstEltToUpdate = + mlir::dyn_cast<cir::IntAttr>(elements[*firstElemToUpdate].element); + isNull = firstEltToUpdate && firstEltToUpdate.isNullValue(); + } + + if (*firstElemToUpdate == *lastElemToUpdate || isNull) { + // All existing bits are either zero or undef. + add(cir::IntAttr::get(charTy, bitsThisChar), offsetInChars, + /*allowOverwrite*/ true); + } else { + cir::IntAttr ci = + mlir::dyn_cast<cir::IntAttr>(elements[*firstElemToUpdate].element); + // In order to perform a partial update, we need the existing bitwise + // value, which we can only extract for a constant int. + if (!ci) + return false; + // Because this is a 1-CharUnit range, the constant occupying it must + // be exactly one CharUnit wide. + assert(ci.getBitWidth() == charWidth && "splitAt failed"); + assert((!(ci.getValue() & updateMask) || allowOverwrite) && + "unexpectedly overwriting bitfield"); + bitsThisChar |= (ci.getValue() & ~updateMask); + elements[*firstElemToUpdate].element = + cir::IntAttr::get(charTy, bitsThisChar); + } + } + + // Stop if we've added all the bits. + if (wantedBits == bits.getBitWidth()) + break; + + // Remove the consumed bits from Bits. + if (!cgm.getDataLayout().isBigEndian()) + bits.lshrInPlace(wantedBits); + bits = bits.trunc(bits.getBitWidth() - wantedBits); + + // The remaining bits go at the start of the following bytes. + offsetWithinChar = 0; + } + + return true; +} + +/// Returns a position within elements such that all elements +/// before the returned index end before pos and all elements at or after +/// the returned index begin at or after pos. Splits elements as necessary +/// to ensure this. Returns std::nullopt if we find something we can't split. +std::optional<size_t> ConstantAggregateBuilder::splitAt(CharUnits pos) { + if (pos >= size) + return elements.size(); + + while (true) { + // Find the first element that starts after pos. + Element *iter = + llvm::upper_bound(elements, pos, [](CharUnits pos, const Element &elt) { + return pos < elt.offset; + }); + + if (iter == elements.begin()) + return 0; + + size_t index = iter - elements.begin() - 1; + const Element &elt = elements[index]; + + // If we already have an element starting at pos, we're done. + if (elt.offset == pos) + return index; + + // Check for overlap with the element that starts before pos. + CharUnits eltEnd = elt.offset + getSize(elt.element); + if (eltEnd <= pos) + return index + 1; + + // Try to decompose it into smaller constants. + if (!split(index, pos)) + return std::nullopt; + } +} + +/// Split the constant at index, if possible. Return true if we did. +/// Hint indicates the location at which we'd like to split, but may be +/// ignored. +bool ConstantAggregateBuilder::split(size_t index, CharUnits hint) { + cgm.errorNYI("split constant at index"); + return false; +} + +void ConstantAggregateBuilder::condense(CharUnits offset, + mlir::Type desiredTy) { + CharUnits desiredSize = getSize(desiredTy); + + std::optional<size_t> firstElemToReplace = splitAt(offset); + if (!firstElemToReplace) + return; + size_t first = *firstElemToReplace; + + std::optional<size_t> lastElemToReplace = splitAt(offset + desiredSize); + if (!lastElemToReplace) + return; + size_t last = *lastElemToReplace; + + size_t length = last - first; + if (length == 0) + return; + + if (length == 1 && elements[first].offset == offset && + getSize(elements[first].element) == desiredSize) { + cgm.errorNYI("re-wrapping single element records"); + return; + } + + // Build a new constant from the elements in the range. + SmallVector<Element> subElems(elements.begin() + first, + elements.begin() + last); + mlir::Attribute replacement = + buildFrom(cgm, subElems, offset, desiredSize, + /*naturalLayout=*/false, desiredTy, false); + + // Replace the range with the condensed constant. + Element newElt(mlir::cast<mlir::TypedAttr>(replacement), offset); + replace(elements, first, last, {newElt}); +} + mlir::Attribute ConstantAggregateBuilder::buildFrom(CIRGenModule &cgm, ArrayRef<Element> elems, CharUnits startOffset, CharUnits size, @@ -301,6 +497,9 @@ private: bool appendBytes(CharUnits fieldOffsetInChars, mlir::TypedAttr initCst, bool allowOverwrite = false); + bool appendBitField(const FieldDecl *field, uint64_t fieldOffset, + cir::IntAttr ci, bool allowOverwrite = false); + bool build(InitListExpr *ile, bool allowOverwrite); bool build(const APValue &val, const RecordDecl *rd, bool isPrimaryBase, const CXXRecordDecl *vTableClass, CharUnits baseOffset); @@ -325,6 +524,30 @@ bool ConstRecordBuilder::appendBytes(CharUnits fieldOffsetInChars, return builder.add(initCst, startOffset + fieldOffsetInChars, allowOverwrite); } +bool ConstRecordBuilder::appendBitField(const FieldDecl *field, + uint64_t fieldOffset, cir::IntAttr ci, + bool allowOverwrite) { + const CIRGenRecordLayout &rl = + cgm.getTypes().getCIRGenRecordLayout(field->getParent()); + const CIRGenBitFieldInfo &info = rl.getBitFieldInfo(field); + llvm::APInt fieldValue = ci.getValue(); + + // Promote the size of FieldValue if necessary + // FIXME: This should never occur, but currently it can because initializer + // constants are cast to bool, and because clang is not enforcing bitfield + // width limits. + if (info.size > fieldValue.getBitWidth()) + fieldValue = fieldValue.zext(info.size); + + // Truncate the size of FieldValue to the bit field size. + if (info.size < fieldValue.getBitWidth()) + fieldValue = fieldValue.trunc(info.size); + + return builder.addBits(fieldValue, + cgm.getASTContext().toBits(startOffset) + fieldOffset, + allowOverwrite); +} + bool ConstRecordBuilder::build(InitListExpr *ile, bool allowOverwrite) { RecordDecl *rd = ile->getType() ->castAs<clang::RecordType>() @@ -407,12 +630,14 @@ bool ConstRecordBuilder::build(InitListExpr *ile, bool allowOverwrite) { } else { // Otherwise we have a bitfield. if (auto constInt = dyn_cast<cir::IntAttr>(eltInit)) { - assert(!cir::MissingFeatures::bitfields()); - cgm.errorNYI(field->getSourceRange(), "bitfields"); + if (!appendBitField(field, layout.getFieldOffset(index), constInt, + allowOverwrite)) + return false; + } else { + // We are trying to initialize a bitfield with a non-trivial constant, + // this must require run-time code. + return false; } - // We are trying to initialize a bitfield with a non-trivial constant, - // this must require run-time code. - return false; } } @@ -510,8 +735,16 @@ bool ConstRecordBuilder::build(const APValue &val, const RecordDecl *rd, if (field->hasAttr<NoUniqueAddressAttr>()) allowOverwrite = true; } else { - assert(!cir::MissingFeatures::bitfields()); - cgm.errorNYI(field->getSourceRange(), "bitfields"); + // Otherwise we have a bitfield. + if (auto constInt = dyn_cast<cir::IntAttr>(eltInit)) { + if (!appendBitField(field, layout.getFieldOffset(index) + offsetBits, + constInt, allowOverwrite)) + return false; + } else { + // We are trying to initialize a bitfield with a non-trivial constant, + // this must require run-time code. + return false; + } } } |