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JIT: Ensure proper alignment of async resumption data section #121790

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JIT: Ensure proper alignment of async resumption data section #121790

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101 changes: 54 additions & 47 deletions src/coreclr/jit/emit.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7873,9 +7873,6 @@ UNATIVE_OFFSET emitter::emitFindOffset(const insGroup* ig, unsigned insNum) cons
//
UNATIVE_OFFSET emitter::emitDataGenBeg(unsigned size, unsigned alignment, var_types dataType)
{
unsigned secOffs;
dataSection* secDesc;

assert(emitDataSecCur == nullptr);

// The size must not be zero and must be a multiple of MIN_DATA_ALIGN
Expand All @@ -7886,46 +7883,16 @@ UNATIVE_OFFSET emitter::emitDataGenBeg(unsigned size, unsigned alignment, var_ty
// simpler to allow it than to check and block it.
//
assert((size != 0) && ((size % dataSection::MIN_DATA_ALIGN) == 0));
assert(isPow2(alignment) && (alignment <= dataSection::MAX_DATA_ALIGN));

/* Get hold of the current offset */
secOffs = emitConsDsc.dsdOffs;

if (((secOffs % alignment) != 0) && (alignment > dataSection::MIN_DATA_ALIGN))
{
// As per the above comment, the minimum alignment is actually (MIN_DATA_ALIGN)
// bytes so we don't need to make any adjustments if the requested
// alignment is less than MIN_DATA_ALIGN.
//
// The maximum requested alignment is tracked and the memory allocator
// will end up ensuring offset 0 is at an address matching that
// alignment. So if the requested alignment is greater than MIN_DATA_ALIGN,
// we need to pad the space out so the offset is a multiple of the requested.
//
uint8_t zeros[dataSection::MAX_DATA_ALIGN] = {}; // auto initialize to all zeros

unsigned zeroSize = alignment - (secOffs % alignment);
unsigned zeroAlign = dataSection::MIN_DATA_ALIGN;
var_types zeroType = TYP_INT;

emitBlkConst(&zeros, zeroSize, zeroAlign, zeroType);
secOffs = emitConsDsc.dsdOffs;
}

assert((secOffs % alignment) == 0);
if (emitConsDsc.alignment < alignment)
{
JITDUMP("Increasing data section alignment from %u to %u for type %s\n", emitConsDsc.alignment, alignment,
varTypeName(dataType));
emitConsDsc.alignment = alignment;
}
emitEnsureDataSectionAlignment(alignment);

unsigned secOffs = emitConsDsc.dsdOffs;
/* Advance the current offset */
emitConsDsc.dsdOffs += size;

/* Allocate a data section descriptor and add it to the list */

secDesc = emitDataSecCur = (dataSection*)emitGetMem(roundUp(sizeof(*secDesc) + size));
dataSection* secDesc = emitDataSecCur = (dataSection*)emitGetMem(roundUp(sizeof(*secDesc) + size));

secDesc->dsSize = size;

Expand All @@ -7948,6 +7915,50 @@ UNATIVE_OFFSET emitter::emitDataGenBeg(unsigned size, unsigned alignment, var_ty
return secOffs;
}

//---------------------------------------------------------------------------
// emitEnsureDataSectionAlignment:
// Ensure that data is emitted such that the next byte would be aligned at
// the specified alignment. Also increase the overall data section alignment
// if necessary.
//
// Arguments:
// alignment - The aligment
//
void emitter::emitEnsureDataSectionAlignment(unsigned alignment)
{
assert(isPow2(alignment) && (alignment <= dataSection::MAX_DATA_ALIGN));

if (emitConsDsc.alignment < alignment)
{
JITDUMP("Increasing overall data section alignment from %u to %u\n", emitConsDsc.alignment, alignment);
emitConsDsc.alignment = alignment;
}

unsigned secOffs = emitConsDsc.dsdOffs;
if ((secOffs % alignment) == 0)
{
return;
}

// Should always be aligned to the minimum alignment.
assert((secOffs % dataSection::MIN_DATA_ALIGN) == 0);

// The maximum requested alignment is tracked and the memory allocator
// will end up ensuring offset 0 is at an address matching that
// alignment. So if the requested alignment is greater than MIN_DATA_ALIGN,
// we need to pad the space out so the offset is a multiple of the requested.
//
uint8_t zeros[dataSection::MAX_DATA_ALIGN] = {}; // auto initialize to all zeros

unsigned zeroSize = alignment - (secOffs % alignment);
unsigned zeroAlign = dataSection::MIN_DATA_ALIGN;
var_types zeroType = TYP_INT;

emitBlkConst(zeros, zeroSize, zeroAlign, zeroType);

assert((emitConsDsc.dsdOffs % alignment) == 0);
}

// Start generating a constant data section for the current function
// populated with BasicBlock references.
// You can choose the references to be either absolute pointers, or
Expand All @@ -7962,16 +7973,11 @@ UNATIVE_OFFSET emitter::emitBBTableDataGenBeg(unsigned numEntries, bool relative

assert(emitDataSecCur == nullptr);

UNATIVE_OFFSET emittedSize;
unsigned elemSize = relativeAddr ? 4 : TARGET_POINTER_SIZE;

if (relativeAddr)
{
emittedSize = numEntries * 4;
}
else
{
emittedSize = numEntries * TARGET_POINTER_SIZE;
}
emitEnsureDataSectionAlignment(elemSize);

UNATIVE_OFFSET emittedSize = numEntries * elemSize;

/* Get hold of the current offset */

Expand Down Expand Up @@ -8018,6 +8024,8 @@ UNATIVE_OFFSET emitter::emitBBTableDataGenBeg(unsigned numEntries, bool relative
//
void emitter::emitAsyncResumeTable(unsigned numEntries, UNATIVE_OFFSET* dataSecOffs, emitter::dataSection** dataSec)
{
emitEnsureDataSectionAlignment(TARGET_POINTER_SIZE);

UNATIVE_OFFSET secOffs = emitConsDsc.dsdOffs;
unsigned emittedSize = sizeof(emitter::dataAsyncResumeInfo) * numEntries;
emitConsDsc.dsdOffs += emittedSize;
Expand All @@ -8041,8 +8049,7 @@ void emitter::emitAsyncResumeTable(unsigned numEntries, UNATIVE_OFFSET* dataSecO
emitConsDsc.dsdList = secDesc;
}

emitConsDsc.dsdLast = secDesc;
emitConsDsc.alignment = std::max(emitConsDsc.alignment, (UNATIVE_OFFSET)TARGET_POINTER_SIZE);
emitConsDsc.dsdLast = secDesc;

*dataSecOffs = secOffs;
*dataSec = secDesc;
Expand Down
2 changes: 2 additions & 0 deletions src/coreclr/jit/emitpub.h
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Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,8 @@ const char* emitOffsetToLabel(unsigned offs);

UNATIVE_OFFSET emitDataGenBeg(unsigned size, unsigned alignment, var_types dataType);

void emitEnsureDataSectionAlignment(unsigned alignment);

UNATIVE_OFFSET emitBBTableDataGenBeg(unsigned numEntries, bool relativeAddr);

void emitDataGenData(unsigned offs, const void* data, UNATIVE_OFFSET size);
Expand Down
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