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[JITLink] Don't under-align zero-fill sections.

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If content sections have lower alignment than zero-fill sections then bump the
overall segment alignment to avoid under-aligning the zero-fill sections.

llvm-svn: 370072
This commit is contained in:
Lang Hames 2019-08-27 15:22:23 +00:00
parent 7bb0bc7bff
commit 20a640eda8
2 changed files with 27 additions and 26 deletions
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39
lib/ExecutionEngine/JITLink/JITLinkGeneric.cpp
View File

@ -238,60 +238,47 @@ Error JITLinkerBase::allocateSegments(const SegmentLayoutMap &Layout) {
// Calculate segment content size. // Calculate segment content size.
size_t SegContentSize = 0; size_t SegContentSize = 0;
uint32_t SegContentAlign = 1;
for (auto &SI : SegLayout.ContentSections) { for (auto &SI : SegLayout.ContentSections) {
assert(!SI.S->atoms_empty() && "Sections in layout must not be empty"); assert(!SI.S->atoms_empty() && "Sections in layout must not be empty");
assert(!SI.Atoms.empty() && "Section layouts must not be empty"); assert(!SI.Atoms.empty() && "Section layouts must not be empty");
// Bump to section alignment before processing atoms. // Bump to section alignment before processing atoms.
SegContentSize = alignTo(SegContentSize, SI.S->getAlignment()); SegContentSize = alignTo(SegContentSize, SI.S->getAlignment());
SegContentAlign = std::max(SegContentAlign, SI.S->getAlignment());
for (auto *DA : SI.Atoms) { for (auto *DA : SI.Atoms) {
SegContentSize = alignTo(SegContentSize, DA->getAlignment()); SegContentSize = alignTo(SegContentSize, DA->getAlignment());
SegContentSize += DA->getSize(); SegContentSize += DA->getSize();
SegContentAlign = std::max(SegContentAlign, DA->getAlignment());
} }
} }
// Get segment content alignment.
unsigned SegContentAlign = 1;
if (!SegLayout.ContentSections.empty()) {
auto &FirstContentSection = SegLayout.ContentSections.front();
SegContentAlign =
std::max(FirstContentSection.S->getAlignment(),
FirstContentSection.Atoms.front()->getAlignment());
}
// Calculate segment zero-fill size. // Calculate segment zero-fill size.
uint64_t SegZeroFillSize = 0; uint64_t SegZeroFillSize = 0;
uint32_t SegZeroFillAlign = 1;
for (auto &SI : SegLayout.ZeroFillSections) { for (auto &SI : SegLayout.ZeroFillSections) {
assert(!SI.S->atoms_empty() && "Sections in layout must not be empty"); assert(!SI.S->atoms_empty() && "Sections in layout must not be empty");
assert(!SI.Atoms.empty() && "Section layouts must not be empty"); assert(!SI.Atoms.empty() && "Section layouts must not be empty");
// Bump to section alignment before processing atoms. // Bump to section alignment before processing atoms.
SegZeroFillSize = alignTo(SegZeroFillSize, SI.S->getAlignment()); SegZeroFillSize = alignTo(SegZeroFillSize, SI.S->getAlignment());
SegZeroFillAlign = std::max(SegZeroFillAlign, SI.S->getAlignment());
for (auto *DA : SI.Atoms) { for (auto *DA : SI.Atoms) {
SegZeroFillSize = alignTo(SegZeroFillSize, DA->getAlignment()); SegZeroFillSize = alignTo(SegZeroFillSize, DA->getAlignment());
SegZeroFillSize += DA->getSize(); SegZeroFillSize += DA->getSize();
SegZeroFillAlign = std::max(SegZeroFillAlign, SI.S->getAlignment());
} }
} }
// Calculate segment zero-fill alignment. assert(isPowerOf2_32(SegContentAlign) &&
uint32_t SegZeroFillAlign = 1; "Expected content alignment to be power of 2");
assert(isPowerOf2_32(SegZeroFillAlign) &&
if (!SegLayout.ZeroFillSections.empty()) { "Expected zero-fill alignment to be power of 2");
auto &FirstZeroFillSection = SegLayout.ZeroFillSections.front(); // Round content alignment up to segment alignment.
SegZeroFillAlign = SegContentAlign = std::max(SegContentAlign, SegZeroFillAlign);
std::max(FirstZeroFillSection.S->getAlignment(),
FirstZeroFillSection.Atoms.front()->getAlignment());
}
if (SegContentSize == 0)
SegContentAlign = SegZeroFillAlign;
if (SegContentAlign % SegZeroFillAlign != 0)
return make_error<JITLinkError>("First content atom alignment does not "
"accommodate first zero-fill atom "
"alignment");
Segments[Prot] = {SegContentSize, SegContentAlign, SegZeroFillSize, Segments[Prot] = {SegContentSize, SegContentAlign, SegZeroFillSize,
SegZeroFillAlign}; SegZeroFillAlign};

14
test/ExecutionEngine/JITLink/X86/MachO_zero_fill_alignment.s Normal file
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@ -0,0 +1,14 @@
# RUN: rm -rf %t && mkdir -p %t
# RUN: llvm-mc -triple=x86_64-apple-macosx10.9 -filetype=obj -o %t/macho_zero_fill_align.o %s
# RUN: llvm-jitlink -noexec %t/macho_zero_fill_align.o -entry higher_zero_fill_align
.section __DATA,__data
.globl low_aligned_data
.p2align 0
low_aligned_data:
.byte 42
.globl higher_zero_fill_align
.zerofill __DATA,__zero_fill,higher_zero_fill_align,8,3
.subsections_via_symbols