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[ADT] Always use 32-bit size type for SmallVector with 16-bit elements #95536

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Merged
merged 4 commits into from
Jun 26, 2024
Merged

[ADT] Always use 32-bit size type for SmallVector with 16-bit elements #95536

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01d0bea
[ADT] Always use 32-bit size type for SmallVector with 16-bit elements
jayfoad Jun 14, 2024
d025afa
Update llvm/include/llvm/ADT/SmallVector.h
jayfoad Jun 14, 2024
04d78ce
Add static_assert
jayfoad Jun 15, 2024
79ce4d8
Merge remote-tracking branch 'origin/main' into smallvector-16-bit
jayfoad Jun 26, 2024
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3 changes: 1 addition & 2 deletions llvm/include/llvm/ADT/SmallVector.h
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Original file line number Diff line number Diff line change
Expand Up @@ -116,8 +116,7 @@ template <class Size_T> class SmallVectorBase {

template <class T>
using SmallVectorSizeType =
std::conditional_t<sizeof(T) < 4 && sizeof(void *) >= 8, uint64_t,
uint32_t>;
std::conditional_t<sizeof(T) == 1, size_t, uint32_t>;

/// Figure out the offset of the first element.
template <class T, typename = void> struct SmallVectorAlignmentAndSize {
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12 changes: 8 additions & 4 deletions llvm/lib/Support/SmallVector.cpp
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Expand Up @@ -37,9 +37,7 @@ struct Struct32B {
#pragma GCC diagnostic pop
#endif
}
static_assert(sizeof(SmallVector<void *, 0>) ==
sizeof(unsigned) * 2 + sizeof(void *),
"wasted space in SmallVector size 0");

static_assert(alignof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
"wrong alignment for 16-byte aligned T");
static_assert(alignof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
Expand All @@ -48,13 +46,19 @@ static_assert(sizeof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
"missing padding for 16-byte aligned T");
static_assert(sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
"missing padding for 32-byte aligned T");

static_assert(sizeof(SmallVector<void *, 0>) ==
sizeof(unsigned) * 2 + sizeof(void *),
"wasted space in SmallVector size 0");
static_assert(sizeof(SmallVector<void *, 1>) ==
sizeof(unsigned) * 2 + sizeof(void *) * 2,
"wasted space in SmallVector size 1");

static_assert(sizeof(SmallVector<char, 0>) ==
sizeof(void *) * 2 + sizeof(void *),
"1 byte elements have word-sized type for size and capacity");
static_assert(sizeof(SmallVector<int16_t, 0>) ==
sizeof(unsigned) * 2 + sizeof(void *),
"2 byte elements have 32-bit type for size and capacity");

/// Report that MinSize doesn't fit into this vector's size type. Throws
/// std::length_error or calls report_fatal_error.
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