mirror of
https://github.com/revng/revng
synced 2026-06-21 14:07:57 +00:00
Alessandro Di Federico
80 lines
2.6 KiB
C++
80 lines
2.6 KiB
C++
//
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// This file is distributed under the MIT License. See LICENSE.md for details.
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//
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#include "revng/Support/Assert.h"
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#include "revng/Support/Debug.h"
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#include "revng-c/DataLayoutAnalysis/DLATypeSystem.h"
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#include "FieldSizeComputation.h"
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uint64_t getFieldSize(const dla::LayoutTypeSystemNode *Child,
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const dla::TypeLinkTag *EdgeTag) {
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uint64_t Result = 0ULL;
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auto ChildSize = Child->Size;
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revng_assert(ChildSize > 0ULL);
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switch (EdgeTag->getKind()) {
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case dla::TypeLinkTag::LK_Instance: {
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const dla::OffsetExpression &OE = EdgeTag->getOffsetExpr();
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revng_assert(OE.Strides.size() == OE.TripCounts.size());
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// Ignore stuff at negative offsets.
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revng_assert(OE.Offset >= 0ULL);
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// If we have an array, we have to compute its size, taking into
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// account the strides and the trip counts.
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// In an OffsetExpression the larger strides come first, so we need to build
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// the instance bottom-up, in reverse, starting from the smaller strides.
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uint64_t PrevStride = 0ULL;
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for (const auto &[TripCount, Stride] :
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llvm::reverse(llvm::zip(OE.TripCounts, OE.Strides))) {
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revng_assert(not PrevStride or PrevStride < Stride);
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revng_assert(Stride > 0ULL);
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auto StrideSize = Stride;
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// If we have a TripCount, we expect it to be strictly positive.
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revng_assert(not TripCount.has_value() or TripCount.value() > 0ULL);
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// Arrays with unknown numbers of elements are considered as if
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// they had a single element
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auto NumElems = TripCount.has_value() ? TripCount.value() : 1;
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revng_assert(NumElems);
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// Here we are computing the larger size that is known to be
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// accessed. So if we have an array, we consider it to be one
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// element shorter than expected, and we add ChildSize only once
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// at the end.
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// This is equivalent to:
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// ChildSize = (NumElems * StrideSize) - (StrideSize - ChildSize);
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ChildSize = ((NumElems - 1) * StrideSize) + ChildSize;
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}
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revng_assert(ChildSize);
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Result = ChildSize;
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} break;
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default:
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revng_unreachable("unexpected edge");
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}
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return Result;
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}
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uint64_t getFieldUpperMember(const dla::LayoutTypeSystemNode *Child,
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const dla::TypeLinkTag *EdgeTag) {
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auto ChildSize = getFieldSize(Child, EdgeTag);
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revng_assert(ChildSize > 0ULL);
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uint64_t ChildOffset = 0ULL;
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if (EdgeTag->getKind() == dla::TypeLinkTag::LK_Instance) {
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const dla::OffsetExpression &OE = EdgeTag->getOffsetExpr();
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ChildOffset = std::max<int64_t>(OE.Offset, ChildOffset);
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}
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return ChildOffset + ChildSize;
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}
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