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Differential D72225 Diff 236526 llvm/lib/MC/MCAssembler.cpp

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llvm/lib/MC/MCAssembler.cpp

Show First 20 Lines • Show All 599 Lines • ▼ Show 20 Linesstatic void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
case MCFragment::FT_LEB: { case MCFragment::FT_LEB: {
const MCLEBFragment &LF = cast<MCLEBFragment>(F); const MCLEBFragment &LF = cast<MCLEBFragment>(F);
OS << LF.getContents(); OS << LF.getContents();
break; break;
} }
case MCFragment::FT_BoundaryAlign: { case MCFragment::FT_BoundaryAlign: {
const MCBoundaryAlignFragment &BF = cast<MCBoundaryAlignFragment>(F);
if (BF.hasEmitNops()) {
if (!Asm.getBackend().writeNopData(OS, FragmentSize)) if (!Asm.getBackend().writeNopData(OS, FragmentSize))
report_fatal_error("unable to write nop sequence of " + report_fatal_error("unable to write nop sequence of " +
Twine(FragmentSize) + " bytes"); Twine(FragmentSize) + " bytes");
} else if (BF.hasValue()) {
for (uint64_t i = 0; i != FragmentSize; ++i)
OS << char(BF.getValue());
LuoYuankeUnsubmitted
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Why we declare Value as int64_t in MCAlignFragment? It seems only 1 byte is needed. Or we add assert(BF.getValueSize() == 1)?

LuoYuanke: Why we declare Value as int64_t in MCAlignFragment? It seems only 1 byte is needed. Or we add…
skanAuthorUnsubmitted
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I didn't decalre Value as int64_t, I declared it as Optional<uint8_t>

skan: I didn't decalre `Value` as `int64_t`, I declared it as `Optional<uint8_t>`
LuoYuankeUnsubmitted
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You are right.

LuoYuanke: You are right.
}
break; break;
} }
case MCFragment::FT_SymbolId: { case MCFragment::FT_SymbolId: {
const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F); const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F);
support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian); support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian);
break; break;
} }
▲ Show 20 Lines • Show All 362 Lines • ▼ Show 20 Lines
static bool needPadding(uint64_t StartAddr, uint64_t Size, static bool needPadding(uint64_t StartAddr, uint64_t Size,
Align BoundaryAlignment) { Align BoundaryAlignment) {
return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) || return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) ||
isAgainstBoundary(StartAddr, Size, BoundaryAlignment); isAgainstBoundary(StartAddr, Size, BoundaryAlignment);
} }
bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout, bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout,
MCBoundaryAlignFragment &BF) { MCBoundaryAlignFragment &BF) {
// The MCBoundaryAlignFragment that doesn't emit NOP should not be relaxed. // The MCBoundaryAlignFragment that does not emit anything or not have any
if (!BF.canEmitNops()) // fragment to be aligned should not be relaxed.
if (!BF.hasEmit() || !BF.getFragment())
return false; return false;
uint64_t AlignedOffset = Layout.getFragmentOffset(BF.getNextNode()); // Compute the size of all the fragments in the range we're trying to align.
uint64_t AlignedSize = 0; const MCFragment *TF = BF.getFragment();
const MCFragment *F = BF.getNextNode(); uint64_t AlignedSize = computeFragmentSize(Layout, *TF);
// If the branch is unfused, it is emitted into one fragment, otherwise it is uint64_t AlignedOffset = Layout.getFragmentOffset(TF);
// emitted into two fragments at most, the next MCBoundaryAlignFragment(if for (auto *F = TF->getPrevNode(); !isa<MCBoundaryAlignFragment>(F);
MaskRayUnsubmitted
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Is it guaranteed F->getPrevNode() will not be executed on the first Fragment?

MaskRay: Is it guaranteed `F->getPrevNode()` will not be executed on the first Fragment?
// exists) also marks the end of the branch. F = F->getPrevNode()) {
for (auto i = 0, N = BF.isFused() ? 2 : 1; uint64_t Size = computeFragmentSize(Layout, *F);
i != N && !isa<MCBoundaryAlignFragment>(F); ++i, F = F->getNextNode()) { AlignedSize += Size;
AlignedSize += computeFragmentSize(Layout, *F); AlignedOffset -= Size;
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AlignedOffset can be defined after AlignedSize is computed.

MaskRay: `AlignedOffset` can be defined after AlignedSize is computed.
skanAuthorUnsubmitted
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Sorry, I didn't get your point.

skan: Sorry, I didn't get your point.
} }
uint64_t OldSize = BF.getSize();
AlignedOffset -= OldSize; // Compute the size of all the MCBoundaryAlignFragments in the range
// [BF,BF.getFragment).
uint64_t FixedValue = [&]() {
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FixedValue doesn't have to be an immediately invoked function expression.

MaskRay: FixedValue doesn't have to be an immediately invoked function expression.
uint64_t N = 0;
for (const MCFragment *F = &BF; F != TF; F = F->getNextNode())
if (auto *MBF = dyn_cast<MCBoundaryAlignFragment>(F))
N += MBF->getSize();
return N;
}();
AlignedOffset -= FixedValue;
Align BoundaryAlignment = BF.getAlignment(); Align BoundaryAlignment = BF.getAlignment();
uint64_t NewSize = needPadding(AlignedOffset, AlignedSize, BoundaryAlignment) uint64_t NewSize = needPadding(AlignedOffset, AlignedSize, BoundaryAlignment)
? offsetToAlignment(AlignedOffset, BoundaryAlignment) ? offsetToAlignment(AlignedOffset, BoundaryAlignment)
: 0U; : 0U;
if (!BF.hasEmitNops()) {
assert((*(BF.getNextNode())).hasInstructions() &&
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*(xxx) -> xxx->

MaskRay: `*(xxx)` -> `xxx->`
"The fragment doesn't have any instruction.");
NewSize = std::min({NewSize,
15 - computeFragmentSize(Layout, *(BF.getNextNode())),
static_cast<uint64_t>(BF.getMaxBytesToEmit())});
assert(computeFragmentSize(Layout, *(BF.getNextNode())) <= 15 &&
"The fragment's size must be no longer than 15 since it should only "
"hold one instruction.");
}
uint64_t OldSize = BF.getSize();
if (NewSize == OldSize) if (NewSize == OldSize)
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if (NewSize == BF.getSize()

MaskRay: `if (NewSize == BF.getSize()`
return false; return false;
BF.setSize(NewSize); BF.setSize(NewSize);
Layout.invalidateFragmentsFrom(&BF); Layout.invalidateFragmentsFrom(&BF);
craig.topperUnsubmitted
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This 15 limit is X86 specific. Seems weird to have it mentioned in a target independent file. Can we abstract this somehow? It can probably happen after the branch.

craig.topper: This 15 limit is X86 specific. Seems weird to have it mentioned in a target independent file.
return true; return true;
} }
bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout, bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
craig.topperUnsubmitted
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Same with this 15.

craig.topper: Same with this 15.
MCDwarfLineAddrFragment &DF) { MCDwarfLineAddrFragment &DF) {
MCContext &Context = Layout.getAssembler().getContext(); MCContext &Context = Layout.getAssembler().getContext();
uint64_t OldSize = DF.getContents().size(); uint64_t OldSize = DF.getContents().size();
int64_t AddrDelta; int64_t AddrDelta;
bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout); bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
assert(Abs && "We created a line delta with an invalid expression"); assert(Abs && "We created a line delta with an invalid expression");
(void)Abs; (void)Abs;
int64_t LineDelta; int64_t LineDelta;
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