MC: Restructure MCAlignFragment as a fixed part and an alignment tail #149030
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Created using spr 1.3.5-bogner
llvmbot
added
backend:RISC-V
backend:WebAssembly
backend:X86
mc
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@llvm/pr-subscribers-mc @llvm/pr-subscribers-backend-risc-v Author: Fangrui Song (MaskRay) ChangesFollow-up to #148544 Patch is 26.86 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/149030.diff 12 Files Affected:
diff --git a/llvm/include/llvm/MC/MCAsmBackend.h b/llvm/include/llvm/MC/MCAsmBackend.h
index 0322cbe6cbe8d..93259b0ea6d74 100644
--- a/llvm/include/llvm/MC/MCAsmBackend.h
+++ b/llvm/include/llvm/MC/MCAsmBackend.h
@@ -18,9 +18,7 @@
namespace llvm {
-class MCAlignFragment;
class MCFragment;
-class MCLEBFragment;
class MCSymbol;
class MCAssembler;
class MCContext;
@@ -108,15 +106,14 @@ class LLVM_ABI MCAsmBackend {
/// Hook to check if extra nop bytes must be inserted for alignment directive.
/// For some targets this may be necessary in order to support linker
/// relaxation. The number of bytes to insert are returned in Size.
- virtual bool shouldInsertExtraNopBytesForCodeAlign(const MCAlignFragment &AF,
+ virtual bool shouldInsertExtraNopBytesForCodeAlign(const MCFragment &AF,
unsigned &Size) {
return false;
}
/// Hook which indicates if the target requires a fixup to be generated when
/// handling an align directive in an executable section
- virtual bool shouldInsertFixupForCodeAlign(MCAssembler &Asm,
- MCAlignFragment &AF) {
+ virtual bool shouldInsertFixupForCodeAlign(MCAssembler &Asm, MCFragment &AF) {
return false;
}
diff --git a/llvm/include/llvm/MC/MCSection.h b/llvm/include/llvm/MC/MCSection.h
index 296fdd8af0d14..5d8fa5680c27d 100644
--- a/llvm/include/llvm/MC/MCSection.h
+++ b/llvm/include/llvm/MC/MCSection.h
@@ -254,6 +254,19 @@ class MCFragment {
uint32_t OperandStart;
uint32_t OperandSize;
} relax;
+ struct {
+ // The alignment to ensure, in bytes.
+ Align Alignment;
+ // The size of the integer (in bytes) of \p Value.
+ uint8_t FillLen;
+ // If true, fill with target-specific nop instructions.
+ bool EmitNops;
+ // The maximum number of bytes to emit; if the alignment
+ // cannot be satisfied in this width then this fragment is ignored.
+ unsigned MaxBytesToEmit;
+ // Value to use for filling padding bytes.
+ int64_t Fill;
+ } align;
struct {
// True if this is a sleb128, false if uleb128.
bool IsSigned;
@@ -441,6 +454,43 @@ class MCFragment {
llvm::copy(Inst, S.begin() + u.relax.OperandStart);
}
+ //== FT_Align functions
+ void makeAlign(Align Alignment, int64_t Fill, uint8_t FillLen,
+ unsigned MaxBytesToEmit) {
+ Kind = FT_Align;
+ u.align.EmitNops = false;
+ u.align.Alignment = Alignment;
+ u.align.Fill = Fill;
+ u.align.FillLen = FillLen;
+ u.align.MaxBytesToEmit = MaxBytesToEmit;
+ }
+
+ Align getAlignment() const {
+ assert(Kind == FT_Align);
+ return u.align.Alignment;
+ }
+ int64_t getAlignFill() const {
+ assert(Kind == FT_Align);
+ return u.align.Fill;
+ }
+ uint8_t getAlignFillLen() const {
+ assert(Kind == FT_Align);
+ return u.align.FillLen;
+ }
+ unsigned getAlignMaxBytesToEmit() const {
+ assert(Kind == FT_Align);
+ return u.align.MaxBytesToEmit;
+ }
+ bool hasAlignEmitNops() const {
+ assert(Kind == FT_Align);
+ return u.align.EmitNops;
+ }
+ void setAlignEmitNops(bool Value, const MCSubtargetInfo *STI) {
+ assert(Kind == FT_Align);
+ u.align.EmitNops = Value;
+ this->STI = STI;
+ }
+
//== FT_LEB functions
const MCExpr &getLEBValue() const {
assert(Kind == FT_LEB);
@@ -486,52 +536,6 @@ class MCEncodedFragment : public MCFragment {
: MCFragment(FType, HasInstructions) {}
};
-class MCAlignFragment : public MCFragment {
- /// Flag to indicate that (optimal) NOPs should be emitted instead
- /// of using the provided value. The exact interpretation of this flag is
- /// target dependent.
- bool EmitNops : 1;
-
- /// The alignment to ensure, in bytes.
- Align Alignment;
-
- /// The size of the integer (in bytes) of \p Value.
- uint8_t FillLen;
-
- /// The maximum number of bytes to emit; if the alignment
- /// cannot be satisfied in this width then this fragment is ignored.
- unsigned MaxBytesToEmit;
-
- /// Value to use for filling padding bytes.
- int64_t Fill;
-
- /// When emitting Nops some subtargets have specific nop encodings.
- const MCSubtargetInfo *STI = nullptr;
-
-public:
- MCAlignFragment(Align Alignment, int64_t Fill, uint8_t FillLen,
- unsigned MaxBytesToEmit)
- : MCFragment(FT_Align, false), EmitNops(false), Alignment(Alignment),
- FillLen(FillLen), MaxBytesToEmit(MaxBytesToEmit), Fill(Fill) {}
-
- Align getAlignment() const { return Alignment; }
- int64_t getFill() const { return Fill; }
- uint8_t getFillLen() const { return FillLen; }
- unsigned getMaxBytesToEmit() const { return MaxBytesToEmit; }
-
- bool hasEmitNops() const { return EmitNops; }
- void setEmitNops(bool Value, const MCSubtargetInfo *STI) {
- EmitNops = Value;
- this->STI = STI;
- }
-
- const MCSubtargetInfo *getSubtargetInfo() const { return STI; }
-
- static bool classof(const MCFragment *F) {
- return F->getKind() == MCFragment::FT_Align;
- }
-};
-
class MCFillFragment : public MCFragment {
uint8_t ValueSize;
/// Value to use for filling bytes.
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index d4d10e0cd74a5..a084af79e9ec8 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -228,25 +228,24 @@ uint64_t MCAssembler::computeFragmentSize(const MCFragment &F) const {
return 4;
case MCFragment::FT_Align: {
- const MCAlignFragment &AF = cast<MCAlignFragment>(F);
- unsigned Offset = getFragmentOffset(AF);
- unsigned Size = offsetToAlignment(Offset, AF.getAlignment());
+ unsigned Offset = F.Offset + F.getFixedSize();
+ unsigned Size = offsetToAlignment(Offset, F.getAlignment());
// Insert extra Nops for code alignment if the target define
// shouldInsertExtraNopBytesForCodeAlign target hook.
- if (AF.getParent()->useCodeAlign() && AF.hasEmitNops() &&
- getBackend().shouldInsertExtraNopBytesForCodeAlign(AF, Size))
- return Size;
+ if (F.getParent()->useCodeAlign() && F.hasAlignEmitNops() &&
+ getBackend().shouldInsertExtraNopBytesForCodeAlign(F, Size))
+ return F.getFixedSize() + Size;
// If we are padding with nops, force the padding to be larger than the
// minimum nop size.
- if (Size > 0 && AF.hasEmitNops()) {
+ if (Size > 0 && F.hasAlignEmitNops()) {
while (Size % getBackend().getMinimumNopSize())
- Size += AF.getAlignment().value();
+ Size += F.getAlignment().value();
}
- if (Size > AF.getMaxBytesToEmit())
- return 0;
- return Size;
+ if (Size > F.getAlignMaxBytesToEmit())
+ Size = 0;
+ return F.getFixedSize() + Size;
}
case MCFragment::FT_Org: {
@@ -416,6 +415,7 @@ static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
switch (F.getKind()) {
case MCFragment::FT_Data:
case MCFragment::FT_Relaxable:
+ case MCFragment::FT_Align:
case MCFragment::FT_LEB:
case MCFragment::FT_Dwarf:
case MCFragment::FT_DwarfFrame:
@@ -429,48 +429,46 @@ static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
const auto &EF = cast<MCFragment>(F);
OS << StringRef(EF.getContents().data(), EF.getContents().size());
OS << StringRef(EF.getVarContents().data(), EF.getVarContents().size());
- break;
- }
- case MCFragment::FT_Align: {
- ++stats::EmittedAlignFragments;
- const MCAlignFragment &AF = cast<MCAlignFragment>(F);
- assert(AF.getFillLen() && "Invalid virtual align in concrete fragment!");
-
- uint64_t Count = FragmentSize / AF.getFillLen();
- assert(FragmentSize % AF.getFillLen() == 0 &&
- "computeFragmentSize computed size is incorrect");
-
- // See if we are aligning with nops, and if so do that first to try to fill
- // the Count bytes. Then if that did not fill any bytes or there are any
- // bytes left to fill use the Value and ValueSize to fill the rest.
- // If we are aligning with nops, ask that target to emit the right data.
- if (AF.hasEmitNops()) {
- if (!Asm.getBackend().writeNopData(OS, Count, AF.getSubtargetInfo()))
- report_fatal_error("unable to write nop sequence of " +
- Twine(Count) + " bytes");
- break;
- }
-
- // Otherwise, write out in multiples of the value size.
- for (uint64_t i = 0; i != Count; ++i) {
- switch (AF.getFillLen()) {
- default: llvm_unreachable("Invalid size!");
- case 1:
- OS << char(AF.getFill());
- break;
- case 2:
- support::endian::write<uint16_t>(OS, AF.getFill(), Endian);
- break;
- case 4:
- support::endian::write<uint32_t>(OS, AF.getFill(), Endian);
- break;
- case 8:
- support::endian::write<uint64_t>(OS, AF.getFill(), Endian);
- break;
+ if (F.getKind() == MCFragment::FT_Align) {
+ ++stats::EmittedAlignFragments;
+ assert(F.getAlignFillLen() &&
+ "Invalid virtual align in concrete fragment!");
+
+ uint64_t Count = (FragmentSize - F.getFixedSize()) / F.getAlignFillLen();
+ assert((FragmentSize - F.getFixedSize()) % F.getAlignFillLen() == 0 &&
+ "computeFragmentSize computed size is incorrect");
+
+ // See if we are aligning with nops, and if so do that first to try to
+ // fill the Count bytes. Then if that did not fill any bytes or there are
+ // any bytes left to fill use the Value and ValueSize to fill the rest. If
+ // we are aligning with nops, ask that target to emit the right data.
+ if (F.hasAlignEmitNops()) {
+ if (!Asm.getBackend().writeNopData(OS, Count, F.getSubtargetInfo()))
+ report_fatal_error("unable to write nop sequence of " + Twine(Count) +
+ " bytes");
+ } else {
+ // Otherwise, write out in multiples of the value size.
+ for (uint64_t i = 0; i != Count; ++i) {
+ switch (F.getAlignFillLen()) {
+ default:
+ llvm_unreachable("Invalid size!");
+ case 1:
+ OS << char(F.getAlignFill());
+ break;
+ case 2:
+ support::endian::write<uint16_t>(OS, F.getAlignFill(), Endian);
+ break;
+ case 4:
+ support::endian::write<uint32_t>(OS, F.getAlignFill(), Endian);
+ break;
+ case 8:
+ support::endian::write<uint64_t>(OS, F.getAlignFill(), Endian);
+ break;
+ }
+ }
}
}
- break;
- }
+ } break;
case MCFragment::FT_Fill: {
++stats::EmittedFillFragments;
@@ -608,9 +606,7 @@ void MCAssembler::writeSectionData(raw_ostream &OS,
case MCFragment::FT_Align:
// Check that we aren't trying to write a non-zero value into a virtual
// section.
- assert((cast<MCAlignFragment>(F).getFillLen() == 0 ||
- cast<MCAlignFragment>(F).getFill() == 0) &&
- "Invalid align in virtual section!");
+ assert(F.getAlignFill() == 0 && "Invalid align in virtual section!");
break;
case MCFragment::FT_Fill:
assert((cast<MCFillFragment>(F).getValue() == 0) &&
@@ -699,17 +695,22 @@ void MCAssembler::layout() {
for (MCSection &Sec : *this) {
for (MCFragment &F : Sec) {
// Process fragments with fixups here.
- if (F.isEncoded()) {
- auto Contents = F.getContents();
- for (MCFixup &Fixup : F.getFixups()) {
- uint64_t FixedValue;
- MCValue Target;
- evaluateFixup(F, Fixup, Target, FixedValue,
- /*RecordReloc=*/true, Contents);
- }
- // In the variable part, fixup offsets are relative to the fixed part's
- // start. Extend the variable contents to the left to account for the
- // fixed part size.
+ auto Contents = F.getContents();
+ for (MCFixup &Fixup : F.getFixups()) {
+ uint64_t FixedValue;
+ MCValue Target;
+ evaluateFixup(F, Fixup, Target, FixedValue,
+ /*RecordReloc=*/true, Contents);
+ }
+ if (F.getKind() == MCFragment::FT_Align) {
+ // For RISC-V linker relaxation, an alignment relocation might be
+ // needed.
+ if (F.hasAlignEmitNops())
+ getBackend().shouldInsertFixupForCodeAlign(*this, F);
+ } else if (F.getVarFixups().size()) {
+ // In the variable part, fixup offsets are relative to the fixed
+ // part's start. Extend the variable contents to the left to account
+ // for the fixed part size.
Contents = MutableArrayRef(F.getParent()->ContentStorage)
.slice(F.VarContentStart - Contents.size(), F.getSize());
for (MCFixup &Fixup : F.getVarFixups()) {
@@ -718,11 +719,6 @@ void MCAssembler::layout() {
evaluateFixup(F, Fixup, Target, FixedValue,
/*RecordReloc=*/true, Contents);
}
- } else if (auto *AF = dyn_cast<MCAlignFragment>(&F)) {
- // For RISC-V linker relaxation, an alignment relocation might be
- // needed.
- if (AF->hasEmitNops())
- getBackend().shouldInsertFixupForCodeAlign(*this, *AF);
}
}
}
diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index 22dff497911de..f0f1bd485258f 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -379,11 +379,11 @@ static void attemptToFoldSymbolOffsetDifference(const MCAssembler *Asm,
// After layout, during relocation generation, it can be treated as a
// data fragment.
Displacement += F->getSize();
- } else if (auto *AF = dyn_cast<MCAlignFragment>(F);
- AF && Layout && AF->hasEmitNops() &&
+ } else if (F->getKind() == MCFragment::FT_Align && Layout &&
+ F->hasAlignEmitNops() &&
!Asm->getBackend().shouldInsertExtraNopBytesForCodeAlign(
- *AF, Count)) {
- Displacement += Asm->computeFragmentSize(*AF);
+ *F, Count)) {
+ Displacement += Asm->computeFragmentSize(*F);
} else if (auto *FF = dyn_cast<MCFillFragment>(F);
FF && FF->getNumValues().evaluateAsAbsolute(Num)) {
Displacement += Num * FF->getValueSize();
diff --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
index bfe045abe6e53..d01660f640c46 100644
--- a/llvm/lib/MC/MCFragment.cpp
+++ b/llvm/lib/MC/MCFragment.cpp
@@ -73,17 +73,9 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
};
switch (getKind()) {
- case MCFragment::FT_Align: {
- const auto *AF = cast<MCAlignFragment>(this);
- OS << " Align:" << AF->getAlignment().value() << " Fill:" << AF->getFill()
- << " FillLen:" << unsigned(AF->getFillLen())
- << " MaxBytesToEmit:" << AF->getMaxBytesToEmit();
- if (AF->hasEmitNops())
- OS << " Nops";
- break;
- }
case MCFragment::FT_Data:
case MCFragment::FT_Relaxable:
+ case MCFragment::FT_Align:
case MCFragment::FT_LEB:
case MCFragment::FT_Dwarf:
case MCFragment::FT_DwarfFrame: {
@@ -112,6 +104,13 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
OS << ' ';
getInst().dump_pretty(OS);
break;
+ case MCFragment::FT_Align:
+ OS << "\n Align:" << getAlignment().value() << " Fill:" << getAlignFill()
+ << " FillLen:" << unsigned(getAlignFillLen())
+ << " MaxBytesToEmit:" << getAlignMaxBytesToEmit();
+ if (hasAlignEmitNops())
+ OS << " Nops";
+ break;
case MCFragment::FT_LEB: {
OS << " Value:";
getLEBValue().print(OS, nullptr);
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index c0cef0f06c57a..056b30b7df6f2 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -579,8 +579,8 @@ void MCObjectStreamer::emitValueToAlignment(Align Alignment, int64_t Fill,
unsigned MaxBytesToEmit) {
if (MaxBytesToEmit == 0)
MaxBytesToEmit = Alignment.value();
- insert(getContext().allocFragment<MCAlignFragment>(Alignment, Fill, FillLen,
- MaxBytesToEmit));
+ MCFragment *F = getOrCreateDataFragment();
+ F->makeAlign(Alignment, Fill, FillLen, MaxBytesToEmit);
// Update the maximum alignment on the current section if necessary.
MCSection *CurSec = getCurrentSectionOnly();
@@ -591,8 +591,8 @@ void MCObjectStreamer::emitCodeAlignment(Align Alignment,
const MCSubtargetInfo *STI,
unsigned MaxBytesToEmit) {
emitValueToAlignment(Alignment, 0, 1, MaxBytesToEmit);
- auto *F = cast<MCAlignFragment>(getCurrentFragment());
- F->setEmitNops(true, STI);
+ auto *F = getCurrentFragment();
+ F->setAlignEmitNops(true, STI);
// With RISC-V style linker relaxation, mark the section as linker-relaxable
// if the alignment is larger than the minimum NOP size.
unsigned Size;
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 7af240a73f952..c0fad137b9037 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -696,14 +696,15 @@ static void addData(SmallVectorImpl<char> &DataBytes,
if (Frag.hasInstructions())
report_fatal_error("only data supported in data sections");
- if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) {
- if (Align->getFillLen() != 1)
+ llvm::append_range(DataBytes, Frag.getContents());
+ if (Frag.getKind() == MCFragment::FT_Align) {
+ if (Frag.getAlignFillLen() != 1)
report_fatal_error("only byte values supported for alignment");
// If nops are requested, use zeros, as this is the data section.
- uint8_t Value = Align->hasEmitNops() ? 0 : Align->getFill();
+ uint8_t Value = Frag.hasAlignEmitNops() ? 0 : Frag.getAlignFill();
uint64_t Size =
- std::min<uint64_t>(alignTo(DataBytes.size(), Align->getAlignment()),
- DataBytes.size() + Align->getMaxBytesToEmit());
+ std::min<uint64_t>(alignTo(DataBytes.size(), Frag.getAlignment()),
+ DataBytes.size() + Frag.getAlignMaxBytesToEmit());
DataBytes.resize(Size, Value);
} else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) {
int64_t NumValues;
@@ -711,12 +712,10 @@ static void addData(SmallVectorImpl<char> &DataBytes,
llvm_unreachable("The fill should be an assembler constant");
DataBytes.insert(DataBytes.end(), Fill->getValueSize() * NumValues,
Fill->getValue());
+ } else if (Frag.getKind() == MCFragment::FT_LEB) {
+ llvm::append_range(DataBytes, Frag.getVarContents());
} else {
- llvm::append_range(DataBytes, Frag.getContents());
- if (Frag.getKind() == MCFragment::FT_LEB)
- llvm::append_range(DataBytes, Frag.getVarContents());
- else
- assert(Frag.getKind() == MCFragment::FT_Data);
+ assert(Frag.getKind() == MCFragment::FT_Data);
}
}
@@ -1867,8 +1866,7 @@ uint64_t WasmObjectWriter::writeOneObject(MCAssembler &Asm,
const MCFragment &AlignFrag = *nextFrag;
if (AlignFrag.getKind() != MCFragment::FT_Align)
report_fatal_error(".init_array section should be aligned");
- if (cast<MCAlignFragment>(AlignFrag).getAlignment() !=
- Align(is64Bit() ? 8 : 4))
+ if (AlignFrag.getAlignment() != Align(is64Bit() ? 8 : 4))
report_fatal_error(
".init_array section should be aligned for pointers");
diff --git a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
index 7b9f1156f9102..9ed17a9b39516 100644
--- a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
+++ b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
@@ -182,14 +182,14 @@ void LoongArchAsmBackend::applyFixup(const MCFragment &F, const MCFixup &Fixup,
// could satisfy alignment by removing Nops.
// The function returns the total Nops Size we need to insert.
bool LoongArchAsmBackend::shouldInsertExtraNopBytesForCodeAlign(
- const MCAlignFragment &AF, unsigned &Size) {
+ const MCFragment &AF, unsigned &Size) {
// Calculate Nops Size only when linker relaxation enabled.
if (!AF.getSubtargetInfo(...
[truncated]
|
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@llvm/pr-subscribers-backend-webassembly Author: Fangrui Song (MaskRay) ChangesFollow-up to #148544 Patch is 26.86 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/149030.diff 12 Files Affected:
diff --git a/llvm/include/llvm/MC/MCAsmBackend.h b/llvm/include/llvm/MC/MCAsmBackend.h
index 0322cbe6cbe8d..93259b0ea6d74 100644
--- a/llvm/include/llvm/MC/MCAsmBackend.h
+++ b/llvm/include/llvm/MC/MCAsmBackend.h
@@ -18,9 +18,7 @@
namespace llvm {
-class MCAlignFragment;
class MCFragment;
-class MCLEBFragment;
class MCSymbol;
class MCAssembler;
class MCContext;
@@ -108,15 +106,14 @@ class LLVM_ABI MCAsmBackend {
/// Hook to check if extra nop bytes must be inserted for alignment directive.
/// For some targets this may be necessary in order to support linker
/// relaxation. The number of bytes to insert are returned in Size.
- virtual bool shouldInsertExtraNopBytesForCodeAlign(const MCAlignFragment &AF,
+ virtual bool shouldInsertExtraNopBytesForCodeAlign(const MCFragment &AF,
unsigned &Size) {
return false;
}
/// Hook which indicates if the target requires a fixup to be generated when
/// handling an align directive in an executable section
- virtual bool shouldInsertFixupForCodeAlign(MCAssembler &Asm,
- MCAlignFragment &AF) {
+ virtual bool shouldInsertFixupForCodeAlign(MCAssembler &Asm, MCFragment &AF) {
return false;
}
diff --git a/llvm/include/llvm/MC/MCSection.h b/llvm/include/llvm/MC/MCSection.h
index 296fdd8af0d14..5d8fa5680c27d 100644
--- a/llvm/include/llvm/MC/MCSection.h
+++ b/llvm/include/llvm/MC/MCSection.h
@@ -254,6 +254,19 @@ class MCFragment {
uint32_t OperandStart;
uint32_t OperandSize;
} relax;
+ struct {
+ // The alignment to ensure, in bytes.
+ Align Alignment;
+ // The size of the integer (in bytes) of \p Value.
+ uint8_t FillLen;
+ // If true, fill with target-specific nop instructions.
+ bool EmitNops;
+ // The maximum number of bytes to emit; if the alignment
+ // cannot be satisfied in this width then this fragment is ignored.
+ unsigned MaxBytesToEmit;
+ // Value to use for filling padding bytes.
+ int64_t Fill;
+ } align;
struct {
// True if this is a sleb128, false if uleb128.
bool IsSigned;
@@ -441,6 +454,43 @@ class MCFragment {
llvm::copy(Inst, S.begin() + u.relax.OperandStart);
}
+ //== FT_Align functions
+ void makeAlign(Align Alignment, int64_t Fill, uint8_t FillLen,
+ unsigned MaxBytesToEmit) {
+ Kind = FT_Align;
+ u.align.EmitNops = false;
+ u.align.Alignment = Alignment;
+ u.align.Fill = Fill;
+ u.align.FillLen = FillLen;
+ u.align.MaxBytesToEmit = MaxBytesToEmit;
+ }
+
+ Align getAlignment() const {
+ assert(Kind == FT_Align);
+ return u.align.Alignment;
+ }
+ int64_t getAlignFill() const {
+ assert(Kind == FT_Align);
+ return u.align.Fill;
+ }
+ uint8_t getAlignFillLen() const {
+ assert(Kind == FT_Align);
+ return u.align.FillLen;
+ }
+ unsigned getAlignMaxBytesToEmit() const {
+ assert(Kind == FT_Align);
+ return u.align.MaxBytesToEmit;
+ }
+ bool hasAlignEmitNops() const {
+ assert(Kind == FT_Align);
+ return u.align.EmitNops;
+ }
+ void setAlignEmitNops(bool Value, const MCSubtargetInfo *STI) {
+ assert(Kind == FT_Align);
+ u.align.EmitNops = Value;
+ this->STI = STI;
+ }
+
//== FT_LEB functions
const MCExpr &getLEBValue() const {
assert(Kind == FT_LEB);
@@ -486,52 +536,6 @@ class MCEncodedFragment : public MCFragment {
: MCFragment(FType, HasInstructions) {}
};
-class MCAlignFragment : public MCFragment {
- /// Flag to indicate that (optimal) NOPs should be emitted instead
- /// of using the provided value. The exact interpretation of this flag is
- /// target dependent.
- bool EmitNops : 1;
-
- /// The alignment to ensure, in bytes.
- Align Alignment;
-
- /// The size of the integer (in bytes) of \p Value.
- uint8_t FillLen;
-
- /// The maximum number of bytes to emit; if the alignment
- /// cannot be satisfied in this width then this fragment is ignored.
- unsigned MaxBytesToEmit;
-
- /// Value to use for filling padding bytes.
- int64_t Fill;
-
- /// When emitting Nops some subtargets have specific nop encodings.
- const MCSubtargetInfo *STI = nullptr;
-
-public:
- MCAlignFragment(Align Alignment, int64_t Fill, uint8_t FillLen,
- unsigned MaxBytesToEmit)
- : MCFragment(FT_Align, false), EmitNops(false), Alignment(Alignment),
- FillLen(FillLen), MaxBytesToEmit(MaxBytesToEmit), Fill(Fill) {}
-
- Align getAlignment() const { return Alignment; }
- int64_t getFill() const { return Fill; }
- uint8_t getFillLen() const { return FillLen; }
- unsigned getMaxBytesToEmit() const { return MaxBytesToEmit; }
-
- bool hasEmitNops() const { return EmitNops; }
- void setEmitNops(bool Value, const MCSubtargetInfo *STI) {
- EmitNops = Value;
- this->STI = STI;
- }
-
- const MCSubtargetInfo *getSubtargetInfo() const { return STI; }
-
- static bool classof(const MCFragment *F) {
- return F->getKind() == MCFragment::FT_Align;
- }
-};
-
class MCFillFragment : public MCFragment {
uint8_t ValueSize;
/// Value to use for filling bytes.
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index d4d10e0cd74a5..a084af79e9ec8 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -228,25 +228,24 @@ uint64_t MCAssembler::computeFragmentSize(const MCFragment &F) const {
return 4;
case MCFragment::FT_Align: {
- const MCAlignFragment &AF = cast<MCAlignFragment>(F);
- unsigned Offset = getFragmentOffset(AF);
- unsigned Size = offsetToAlignment(Offset, AF.getAlignment());
+ unsigned Offset = F.Offset + F.getFixedSize();
+ unsigned Size = offsetToAlignment(Offset, F.getAlignment());
// Insert extra Nops for code alignment if the target define
// shouldInsertExtraNopBytesForCodeAlign target hook.
- if (AF.getParent()->useCodeAlign() && AF.hasEmitNops() &&
- getBackend().shouldInsertExtraNopBytesForCodeAlign(AF, Size))
- return Size;
+ if (F.getParent()->useCodeAlign() && F.hasAlignEmitNops() &&
+ getBackend().shouldInsertExtraNopBytesForCodeAlign(F, Size))
+ return F.getFixedSize() + Size;
// If we are padding with nops, force the padding to be larger than the
// minimum nop size.
- if (Size > 0 && AF.hasEmitNops()) {
+ if (Size > 0 && F.hasAlignEmitNops()) {
while (Size % getBackend().getMinimumNopSize())
- Size += AF.getAlignment().value();
+ Size += F.getAlignment().value();
}
- if (Size > AF.getMaxBytesToEmit())
- return 0;
- return Size;
+ if (Size > F.getAlignMaxBytesToEmit())
+ Size = 0;
+ return F.getFixedSize() + Size;
}
case MCFragment::FT_Org: {
@@ -416,6 +415,7 @@ static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
switch (F.getKind()) {
case MCFragment::FT_Data:
case MCFragment::FT_Relaxable:
+ case MCFragment::FT_Align:
case MCFragment::FT_LEB:
case MCFragment::FT_Dwarf:
case MCFragment::FT_DwarfFrame:
@@ -429,48 +429,46 @@ static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
const auto &EF = cast<MCFragment>(F);
OS << StringRef(EF.getContents().data(), EF.getContents().size());
OS << StringRef(EF.getVarContents().data(), EF.getVarContents().size());
- break;
- }
- case MCFragment::FT_Align: {
- ++stats::EmittedAlignFragments;
- const MCAlignFragment &AF = cast<MCAlignFragment>(F);
- assert(AF.getFillLen() && "Invalid virtual align in concrete fragment!");
-
- uint64_t Count = FragmentSize / AF.getFillLen();
- assert(FragmentSize % AF.getFillLen() == 0 &&
- "computeFragmentSize computed size is incorrect");
-
- // See if we are aligning with nops, and if so do that first to try to fill
- // the Count bytes. Then if that did not fill any bytes or there are any
- // bytes left to fill use the Value and ValueSize to fill the rest.
- // If we are aligning with nops, ask that target to emit the right data.
- if (AF.hasEmitNops()) {
- if (!Asm.getBackend().writeNopData(OS, Count, AF.getSubtargetInfo()))
- report_fatal_error("unable to write nop sequence of " +
- Twine(Count) + " bytes");
- break;
- }
-
- // Otherwise, write out in multiples of the value size.
- for (uint64_t i = 0; i != Count; ++i) {
- switch (AF.getFillLen()) {
- default: llvm_unreachable("Invalid size!");
- case 1:
- OS << char(AF.getFill());
- break;
- case 2:
- support::endian::write<uint16_t>(OS, AF.getFill(), Endian);
- break;
- case 4:
- support::endian::write<uint32_t>(OS, AF.getFill(), Endian);
- break;
- case 8:
- support::endian::write<uint64_t>(OS, AF.getFill(), Endian);
- break;
+ if (F.getKind() == MCFragment::FT_Align) {
+ ++stats::EmittedAlignFragments;
+ assert(F.getAlignFillLen() &&
+ "Invalid virtual align in concrete fragment!");
+
+ uint64_t Count = (FragmentSize - F.getFixedSize()) / F.getAlignFillLen();
+ assert((FragmentSize - F.getFixedSize()) % F.getAlignFillLen() == 0 &&
+ "computeFragmentSize computed size is incorrect");
+
+ // See if we are aligning with nops, and if so do that first to try to
+ // fill the Count bytes. Then if that did not fill any bytes or there are
+ // any bytes left to fill use the Value and ValueSize to fill the rest. If
+ // we are aligning with nops, ask that target to emit the right data.
+ if (F.hasAlignEmitNops()) {
+ if (!Asm.getBackend().writeNopData(OS, Count, F.getSubtargetInfo()))
+ report_fatal_error("unable to write nop sequence of " + Twine(Count) +
+ " bytes");
+ } else {
+ // Otherwise, write out in multiples of the value size.
+ for (uint64_t i = 0; i != Count; ++i) {
+ switch (F.getAlignFillLen()) {
+ default:
+ llvm_unreachable("Invalid size!");
+ case 1:
+ OS << char(F.getAlignFill());
+ break;
+ case 2:
+ support::endian::write<uint16_t>(OS, F.getAlignFill(), Endian);
+ break;
+ case 4:
+ support::endian::write<uint32_t>(OS, F.getAlignFill(), Endian);
+ break;
+ case 8:
+ support::endian::write<uint64_t>(OS, F.getAlignFill(), Endian);
+ break;
+ }
+ }
}
}
- break;
- }
+ } break;
case MCFragment::FT_Fill: {
++stats::EmittedFillFragments;
@@ -608,9 +606,7 @@ void MCAssembler::writeSectionData(raw_ostream &OS,
case MCFragment::FT_Align:
// Check that we aren't trying to write a non-zero value into a virtual
// section.
- assert((cast<MCAlignFragment>(F).getFillLen() == 0 ||
- cast<MCAlignFragment>(F).getFill() == 0) &&
- "Invalid align in virtual section!");
+ assert(F.getAlignFill() == 0 && "Invalid align in virtual section!");
break;
case MCFragment::FT_Fill:
assert((cast<MCFillFragment>(F).getValue() == 0) &&
@@ -699,17 +695,22 @@ void MCAssembler::layout() {
for (MCSection &Sec : *this) {
for (MCFragment &F : Sec) {
// Process fragments with fixups here.
- if (F.isEncoded()) {
- auto Contents = F.getContents();
- for (MCFixup &Fixup : F.getFixups()) {
- uint64_t FixedValue;
- MCValue Target;
- evaluateFixup(F, Fixup, Target, FixedValue,
- /*RecordReloc=*/true, Contents);
- }
- // In the variable part, fixup offsets are relative to the fixed part's
- // start. Extend the variable contents to the left to account for the
- // fixed part size.
+ auto Contents = F.getContents();
+ for (MCFixup &Fixup : F.getFixups()) {
+ uint64_t FixedValue;
+ MCValue Target;
+ evaluateFixup(F, Fixup, Target, FixedValue,
+ /*RecordReloc=*/true, Contents);
+ }
+ if (F.getKind() == MCFragment::FT_Align) {
+ // For RISC-V linker relaxation, an alignment relocation might be
+ // needed.
+ if (F.hasAlignEmitNops())
+ getBackend().shouldInsertFixupForCodeAlign(*this, F);
+ } else if (F.getVarFixups().size()) {
+ // In the variable part, fixup offsets are relative to the fixed
+ // part's start. Extend the variable contents to the left to account
+ // for the fixed part size.
Contents = MutableArrayRef(F.getParent()->ContentStorage)
.slice(F.VarContentStart - Contents.size(), F.getSize());
for (MCFixup &Fixup : F.getVarFixups()) {
@@ -718,11 +719,6 @@ void MCAssembler::layout() {
evaluateFixup(F, Fixup, Target, FixedValue,
/*RecordReloc=*/true, Contents);
}
- } else if (auto *AF = dyn_cast<MCAlignFragment>(&F)) {
- // For RISC-V linker relaxation, an alignment relocation might be
- // needed.
- if (AF->hasEmitNops())
- getBackend().shouldInsertFixupForCodeAlign(*this, *AF);
}
}
}
diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index 22dff497911de..f0f1bd485258f 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -379,11 +379,11 @@ static void attemptToFoldSymbolOffsetDifference(const MCAssembler *Asm,
// After layout, during relocation generation, it can be treated as a
// data fragment.
Displacement += F->getSize();
- } else if (auto *AF = dyn_cast<MCAlignFragment>(F);
- AF && Layout && AF->hasEmitNops() &&
+ } else if (F->getKind() == MCFragment::FT_Align && Layout &&
+ F->hasAlignEmitNops() &&
!Asm->getBackend().shouldInsertExtraNopBytesForCodeAlign(
- *AF, Count)) {
- Displacement += Asm->computeFragmentSize(*AF);
+ *F, Count)) {
+ Displacement += Asm->computeFragmentSize(*F);
} else if (auto *FF = dyn_cast<MCFillFragment>(F);
FF && FF->getNumValues().evaluateAsAbsolute(Num)) {
Displacement += Num * FF->getValueSize();
diff --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
index bfe045abe6e53..d01660f640c46 100644
--- a/llvm/lib/MC/MCFragment.cpp
+++ b/llvm/lib/MC/MCFragment.cpp
@@ -73,17 +73,9 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
};
switch (getKind()) {
- case MCFragment::FT_Align: {
- const auto *AF = cast<MCAlignFragment>(this);
- OS << " Align:" << AF->getAlignment().value() << " Fill:" << AF->getFill()
- << " FillLen:" << unsigned(AF->getFillLen())
- << " MaxBytesToEmit:" << AF->getMaxBytesToEmit();
- if (AF->hasEmitNops())
- OS << " Nops";
- break;
- }
case MCFragment::FT_Data:
case MCFragment::FT_Relaxable:
+ case MCFragment::FT_Align:
case MCFragment::FT_LEB:
case MCFragment::FT_Dwarf:
case MCFragment::FT_DwarfFrame: {
@@ -112,6 +104,13 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
OS << ' ';
getInst().dump_pretty(OS);
break;
+ case MCFragment::FT_Align:
+ OS << "\n Align:" << getAlignment().value() << " Fill:" << getAlignFill()
+ << " FillLen:" << unsigned(getAlignFillLen())
+ << " MaxBytesToEmit:" << getAlignMaxBytesToEmit();
+ if (hasAlignEmitNops())
+ OS << " Nops";
+ break;
case MCFragment::FT_LEB: {
OS << " Value:";
getLEBValue().print(OS, nullptr);
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index c0cef0f06c57a..056b30b7df6f2 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -579,8 +579,8 @@ void MCObjectStreamer::emitValueToAlignment(Align Alignment, int64_t Fill,
unsigned MaxBytesToEmit) {
if (MaxBytesToEmit == 0)
MaxBytesToEmit = Alignment.value();
- insert(getContext().allocFragment<MCAlignFragment>(Alignment, Fill, FillLen,
- MaxBytesToEmit));
+ MCFragment *F = getOrCreateDataFragment();
+ F->makeAlign(Alignment, Fill, FillLen, MaxBytesToEmit);
// Update the maximum alignment on the current section if necessary.
MCSection *CurSec = getCurrentSectionOnly();
@@ -591,8 +591,8 @@ void MCObjectStreamer::emitCodeAlignment(Align Alignment,
const MCSubtargetInfo *STI,
unsigned MaxBytesToEmit) {
emitValueToAlignment(Alignment, 0, 1, MaxBytesToEmit);
- auto *F = cast<MCAlignFragment>(getCurrentFragment());
- F->setEmitNops(true, STI);
+ auto *F = getCurrentFragment();
+ F->setAlignEmitNops(true, STI);
// With RISC-V style linker relaxation, mark the section as linker-relaxable
// if the alignment is larger than the minimum NOP size.
unsigned Size;
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 7af240a73f952..c0fad137b9037 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -696,14 +696,15 @@ static void addData(SmallVectorImpl<char> &DataBytes,
if (Frag.hasInstructions())
report_fatal_error("only data supported in data sections");
- if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) {
- if (Align->getFillLen() != 1)
+ llvm::append_range(DataBytes, Frag.getContents());
+ if (Frag.getKind() == MCFragment::FT_Align) {
+ if (Frag.getAlignFillLen() != 1)
report_fatal_error("only byte values supported for alignment");
// If nops are requested, use zeros, as this is the data section.
- uint8_t Value = Align->hasEmitNops() ? 0 : Align->getFill();
+ uint8_t Value = Frag.hasAlignEmitNops() ? 0 : Frag.getAlignFill();
uint64_t Size =
- std::min<uint64_t>(alignTo(DataBytes.size(), Align->getAlignment()),
- DataBytes.size() + Align->getMaxBytesToEmit());
+ std::min<uint64_t>(alignTo(DataBytes.size(), Frag.getAlignment()),
+ DataBytes.size() + Frag.getAlignMaxBytesToEmit());
DataBytes.resize(Size, Value);
} else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) {
int64_t NumValues;
@@ -711,12 +712,10 @@ static void addData(SmallVectorImpl<char> &DataBytes,
llvm_unreachable("The fill should be an assembler constant");
DataBytes.insert(DataBytes.end(), Fill->getValueSize() * NumValues,
Fill->getValue());
+ } else if (Frag.getKind() == MCFragment::FT_LEB) {
+ llvm::append_range(DataBytes, Frag.getVarContents());
} else {
- llvm::append_range(DataBytes, Frag.getContents());
- if (Frag.getKind() == MCFragment::FT_LEB)
- llvm::append_range(DataBytes, Frag.getVarContents());
- else
- assert(Frag.getKind() == MCFragment::FT_Data);
+ assert(Frag.getKind() == MCFragment::FT_Data);
}
}
@@ -1867,8 +1866,7 @@ uint64_t WasmObjectWriter::writeOneObject(MCAssembler &Asm,
const MCFragment &AlignFrag = *nextFrag;
if (AlignFrag.getKind() != MCFragment::FT_Align)
report_fatal_error(".init_array section should be aligned");
- if (cast<MCAlignFragment>(AlignFrag).getAlignment() !=
- Align(is64Bit() ? 8 : 4))
+ if (AlignFrag.getAlignment() != Align(is64Bit() ? 8 : 4))
report_fatal_error(
".init_array section should be aligned for pointers");
diff --git a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
index 7b9f1156f9102..9ed17a9b39516 100644
--- a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
+++ b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
@@ -182,14 +182,14 @@ void LoongArchAsmBackend::applyFixup(const MCFragment &F, const MCFixup &Fixup,
// could satisfy alignment by removing Nops.
// The function returns the total Nops Size we need to insert.
bool LoongArchAsmBackend::shouldInsertExtraNopBytesForCodeAlign(
- const MCAlignFragment &AF, unsigned &Size) {
+ const MCFragment &AF, unsigned &Size) {
// Calculate Nops Size only when linker relaxation enabled.
if (!AF.getSubtargetInfo(...
[truncated]
|
aengelke
reviewed
Jul 16, 2025
There was a problem hiding this comment.
We can do this, but I'm unsure about the direction.
Right now we have FT_Data, FT_Align, FT_Data, FT_Align, FT_Data, this changes it to FT_Align, FT_Align, FT_Data.
For targets that rarely use relaxable fragments, e.g. AArch64, we probably want to end up with a single fragment per text section (as opposed to one fragment per function). emitValueToAlignment could check the current alignment and eagerly emit the value/nops if the new alignment is <= previous alignment. With this approach, emitValueToAlignment would need to check the previous fragment for the current alignment, which is not easily accessible, or we would need to cache the current alignment.
I thought about putting the alignment at the beginning of a fragment. Unfortunately, this would likely require to increase the size of MCFragment. We could optimize for the common case (zero fill or nops, no max bytes), we could add this bit and the alignment into existing padding.
| void setAlignEmitNops(bool Value, const MCSubtargetInfo *STI) { | ||
| assert(Kind == FT_Align); | ||
| u.align.EmitNops = Value; | ||
| this->STI = STI; |
There was a problem hiding this comment.
Assert that STI didn't change?
|
As the previous patch shows, the number of FT_Align fragments is far fewer when FT_Relaxable.
The section alignment is the maximum of all FT_Align alignments. The behavior is as if the start has an implicit alignment fragment. |
Created using spr 1.3.5-bogner
MaskRay
changed the title
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Follow-up to #148544