// This assumes the second instruction in the macro-op pair will get
// assigned to its own MCRelaxableFragment. Since all JCC instructions
// are relaxable, we should be safe.
- Streamer.emitNeverAlignCodeAtEnd(/*Alignment to avoid=*/64, *BC.STI);
}
if (!EmitCodeOnly && opts::UpdateDebugSections && BF.getDWARFUnit()) {
public:
enum FragmentType : uint8_t {
FT_Align,
- FT_NeverAlign,
FT_Data,
FT_CompactEncodedInst,
FT_Fill,
}
};
-class MCNeverAlignFragment : public MCFragment {
- /// The alignment the end of the next fragment should avoid.
- unsigned Alignment;
-
- /// When emitting Nops some subtargets have specific nop encodings.
- const MCSubtargetInfo &STI;
-
-public:
- MCNeverAlignFragment(unsigned Alignment, const MCSubtargetInfo &STI,
- MCSection *Sec = nullptr)
- : MCFragment(FT_NeverAlign, false, Sec), Alignment(Alignment), STI(STI) {}
-
- unsigned getAlignment() const { return Alignment; }
-
- const MCSubtargetInfo &getSubtargetInfo() const { return STI; }
-
- static bool classof(const MCFragment *F) {
- return F->getKind() == MCFragment::FT_NeverAlign;
- }
-};
-
class MCFillFragment : public MCFragment {
uint8_t ValueSize;
/// Value to use for filling bytes.
unsigned MaxBytesToEmit = 0) override;
void emitCodeAlignment(unsigned ByteAlignment, const MCSubtargetInfo *STI,
unsigned MaxBytesToEmit = 0) override;
- void emitNeverAlignCodeAtEnd(unsigned ByteAlignment,
- const MCSubtargetInfo &STI) override;
void emitValueToOffset(const MCExpr *Offset, unsigned char Value,
SMLoc Loc) override;
void emitDwarfLocDirective(unsigned FileNo, unsigned Line, unsigned Column,
const MCSubtargetInfo *STI,
unsigned MaxBytesToEmit = 0);
- /// If the end of the fragment following this NeverAlign fragment ever gets
- /// aligned to \p ByteAlignment, this fragment emits a single nop before the
- /// following fragment to break this end-alignment.
- virtual void emitNeverAlignCodeAtEnd(unsigned ByteAlignment,
- const MCSubtargetInfo &STI);
-
/// Emit some number of copies of \p Value until the byte offset \p
/// Offset is reached.
///
return IsResolved;
}
-/// Check if the branch crosses the boundary.
-///
-/// \param StartAddr start address of the fused/unfused branch.
-/// \param Size size of the fused/unfused branch.
-/// \param BoundaryAlignment alignment requirement of the branch.
-/// \returns true if the branch cross the boundary.
-static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size,
- Align BoundaryAlignment) {
- uint64_t EndAddr = StartAddr + Size;
- return (StartAddr >> Log2(BoundaryAlignment)) !=
- ((EndAddr - 1) >> Log2(BoundaryAlignment));
-}
-
-/// Check if the branch is against the boundary.
-///
-/// \param StartAddr start address of the fused/unfused branch.
-/// \param Size size of the fused/unfused branch.
-/// \param BoundaryAlignment alignment requirement of the branch.
-/// \returns true if the branch is against the boundary.
-static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size,
- Align BoundaryAlignment) {
- uint64_t EndAddr = StartAddr + Size;
- return (EndAddr & (BoundaryAlignment.value() - 1)) == 0;
-}
-
-/// Check if the branch needs padding.
-///
-/// \param StartAddr start address of the fused/unfused branch.
-/// \param Size size of the fused/unfused branch.
-/// \param BoundaryAlignment alignment requirement of the branch.
-/// \returns true if the branch needs padding.
-static bool needPadding(uint64_t StartAddr, uint64_t Size,
- Align BoundaryAlignment) {
- return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) ||
- isAgainstBoundary(StartAddr, Size, BoundaryAlignment);
-}
-
uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
const MCFragment &F) const {
assert(getBackendPtr() && "Requires assembler backend");
return Size;
}
- case MCFragment::FT_NeverAlign: {
- // Disclaimer: NeverAlign fragment size depends on the size of its immediate
- // successor, but NeverAlign need not be a MCRelaxableFragment.
- // NeverAlign fragment size is recomputed if the successor is relaxed:
- // - If RelaxableFragment is relaxed, it gets invalidated by marking its
- // predecessor as LastValidFragment.
- // - This forces the assembler to call MCAsmLayout::layoutFragment on that
- // relaxable fragment, which in turn will always ask the predecessor to
- // compute its size (see "computeFragmentSize(prev)" in layoutFragment).
- //
- // In short, the simplest way to ensure that computeFragmentSize() is sane
- // is to establish the following rule: it should never examine fragments
- // after the current fragment in the section. If we logically need to
- // examine any fragment after the current fragment, we need to do that using
- // relaxation, inside MCAssembler::layoutSectionOnce.
- const MCNeverAlignFragment &NAF = cast<MCNeverAlignFragment>(F);
- const MCFragment *NF = F.getNextNode();
- uint64_t Offset = Layout.getFragmentOffset(&NAF);
- size_t NextFragSize = 0;
- if (const auto *NextFrag = dyn_cast<MCRelaxableFragment>(NF)) {
- NextFragSize = NextFrag->getContents().size();
- } else if (const auto *NextFrag = dyn_cast<MCDataFragment>(NF)) {
- NextFragSize = NextFrag->getContents().size();
- } else {
- llvm_unreachable("Didn't find the expected fragment after NeverAlign");
- }
- // Check if the next fragment ends at the alignment we want to avoid.
- if (isAgainstBoundary(Offset, NextFragSize, Align(NAF.getAlignment()))) {
- // Avoid this alignment by introducing minimum nop.
- assert(getBackend().getMinimumNopSize() != NAF.getAlignment());
- return getBackend().getMinimumNopSize();
- }
- return 0;
- }
-
case MCFragment::FT_Org: {
const MCOrgFragment &OF = cast<MCOrgFragment>(F);
MCValue Value;
break;
}
- case MCFragment::FT_NeverAlign: {
- const MCNeverAlignFragment &NAF = cast<MCNeverAlignFragment>(F);
- if (!Asm.getBackend().writeNopData(OS, FragmentSize,
- &NAF.getSubtargetInfo()))
- report_fatal_error("unable to write nop sequence of " +
- Twine(FragmentSize) + " bytes");
- break;
- }
-
case MCFragment::FT_Data:
++stats::EmittedDataFragments;
OS << cast<MCDataFragment>(F).getContents();
return OldSize != LF.getContents().size();
}
+/// Check if the branch crosses the boundary.
+///
+/// \param StartAddr start address of the fused/unfused branch.
+/// \param Size size of the fused/unfused branch.
+/// \param BoundaryAlignment alignment requirement of the branch.
+/// \returns true if the branch cross the boundary.
+static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size,
+ Align BoundaryAlignment) {
+ uint64_t EndAddr = StartAddr + Size;
+ return (StartAddr >> Log2(BoundaryAlignment)) !=
+ ((EndAddr - 1) >> Log2(BoundaryAlignment));
+}
+
+/// Check if the branch is against the boundary.
+///
+/// \param StartAddr start address of the fused/unfused branch.
+/// \param Size size of the fused/unfused branch.
+/// \param BoundaryAlignment alignment requirement of the branch.
+/// \returns true if the branch is against the boundary.
+static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size,
+ Align BoundaryAlignment) {
+ uint64_t EndAddr = StartAddr + Size;
+ return (EndAddr & (BoundaryAlignment.value() - 1)) == 0;
+}
+
+/// Check if the branch needs padding.
+///
+/// \param StartAddr start address of the fused/unfused branch.
+/// \param Size size of the fused/unfused branch.
+/// \param BoundaryAlignment alignment requirement of the branch.
+/// \returns true if the branch needs padding.
+static bool needPadding(uint64_t StartAddr, uint64_t Size,
+ Align BoundaryAlignment) {
+ return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) ||
+ isAgainstBoundary(StartAddr, Size, BoundaryAlignment);
+}
+
bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout,
MCBoundaryAlignFragment &BF) {
// BoundaryAlignFragment that doesn't need to align any fragment should not be
case FT_Align:
delete cast<MCAlignFragment>(this);
return;
- case FT_NeverAlign:
- delete cast<MCNeverAlignFragment>(this);
- return;
case FT_Data:
delete cast<MCDataFragment>(this);
return;
OS << "<";
switch (getKind()) {
case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
- case MCFragment::FT_NeverAlign:
- OS << "MCNeverAlignFragment";
- break;
case MCFragment::FT_Data: OS << "MCDataFragment"; break;
case MCFragment::FT_CompactEncodedInst:
OS << "MCCompactEncodedInstFragment"; break;
<< " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
break;
}
- case MCFragment::FT_NeverAlign: {
- const MCNeverAlignFragment *NAF = cast<MCNeverAlignFragment>(this);
- OS << "\n ";
- OS << " Alignment:" << NAF->getAlignment() << ">";
- break;
- }
case MCFragment::FT_Data: {
const auto *DF = cast<MCDataFragment>(this);
OS << "\n ";
cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true, STI);
}
-void MCObjectStreamer::emitNeverAlignCodeAtEnd(unsigned ByteAlignment,
- const MCSubtargetInfo &STI) {
- insert(new MCNeverAlignFragment(ByteAlignment, STI));
-}
-
void MCObjectStreamer::emitValueToOffset(const MCExpr *Offset,
unsigned char Value,
SMLoc Loc) {
void MCStreamer::emitCodeAlignment(unsigned ByteAlignment,
const MCSubtargetInfo *STI,
unsigned MaxBytesToEmit) {}
-void MCStreamer::emitNeverAlignCodeAtEnd(unsigned ByteAlignment,
- const MCSubtargetInfo &STI) {}
void MCStreamer::emitValueToOffset(const MCExpr *Offset, unsigned char Value,
SMLoc Loc) {}
void MCStreamer::emitBundleAlignMode(unsigned AlignPow2) {}
bool parseDirectiveArch();
bool parseDirectiveNops(SMLoc L);
bool parseDirectiveEven(SMLoc L);
- bool parseDirectiveAvoidEndAlign(SMLoc L);
bool ParseDirectiveCode(StringRef IDVal, SMLoc L);
/// CodeView FPO data directives.
return false;
} else if (IDVal == ".nops")
return parseDirectiveNops(DirectiveID.getLoc());
- else if (IDVal == ".avoid_end_align")
- return parseDirectiveAvoidEndAlign(DirectiveID.getLoc());
else if (IDVal == ".even")
return parseDirectiveEven(DirectiveID.getLoc());
else if (IDVal == ".cv_fpo_proc")
return false;
}
-/// Directive for NeverAlign fragment testing, not for general usage!
-/// parseDirectiveAvoidEndAlign
-/// ::= .avoid_end_align alignment
-bool X86AsmParser::parseDirectiveAvoidEndAlign(SMLoc L) {
- int64_t Alignment = 0;
- SMLoc AlignmentLoc;
- AlignmentLoc = getTok().getLoc();
- if (getParser().checkForValidSection() ||
- getParser().parseAbsoluteExpression(Alignment))
- return true;
-
- if (getParser().parseEOL("unexpected token in directive"))
- return true;
-
- if (Alignment <= 0)
- return Error(AlignmentLoc, "expected a positive alignment");
-
- getParser().getStreamer().emitNeverAlignCodeAtEnd(Alignment, getSTI());
- return false;
-}
-
/// ParseDirectiveCode
/// ::= .code16 | .code32 | .code64
bool X86AsmParser::ParseDirectiveCode(StringRef IDVal, SMLoc L) {
+++ /dev/null
-# RUN: llvm-mc -triple=x86_64 -filetype=obj %s | llvm-objdump --no-show-raw-insn -d - | FileCheck %s
-# RUN: not llvm-mc -triple=x86_64 --defsym ERR=1 %s -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR
-
-# avoid_end_align has no effect since test doesn't end at alignment boundary:
-.avoid_end_align 64
-# CHECK-NOT: nop
- testl %eax, %eax
-# CHECK: testl %eax, %eax
- je .LBB0
-
-.fill 58, 1, 0x00
-# NeverAlign followed by MCDataFragment:
-# avoid_end_align inserts nop because `test` would end at alignment boundary:
-.avoid_end_align 64
-# CHECK: 3e: nop
- testl %eax, %eax
-# CHECK-NEXT: 3f: testl %eax, %eax
- je .LBB0
-# CHECK-NEXT: 41: je
-.LBB0:
- retq
-
-.p2align 6
-.L0:
-.nops 57
- int3
-# NeverAlign followed by RelaxableFragment:
-.avoid_end_align 64
-# CHECK: ba: nop
- cmpl $(.L1-.L0), %eax
-# CHECK-NEXT: bb: cmpl
- je .L0
-# CHECK-NEXT: c1: je
-.nops 65
-.L1:
-
-###############################################################################
-# Experiment A:
-# Check that NeverAlign doesn't introduce infinite loops in layout.
-# Control:
-# 1. NeverAlign fragment is not added,
-# 2. Short formats of cmp and jcc are used (3 and 2 bytes respectively),
-# 3. cmp and jcc are placed such that to be split by 64B alignment boundary.
-# 4. jcc would be relaxed to a longer format if at least one byte is added
-# between .L10 and je itself, e.g. by adding a NeverAlign padding byte,
-# or relaxing cmp instruction.
-# 5. cmp would be relaxed to a longer format if at least one byte is added
-# between .L11 and .L12, e.g. due to relaxing jcc instruction.
-.p2align 6
-# CHECK: 140: int3
-.fill 2, 1, 0xcc
-.L10:
-.nops 122
- int3
-# CHECK: 1bc: int3
-# no avoid_end_align here
-# CHECK-NOT: nop
- cmp $(.L12-.L11), %eax
-# CHECK: 1bd: cmpl
-.L11:
- je .L10
-# CHECK-NEXT: 1c0: je
-.nops 125
-.L12:
-
-# Experiment:
-# Same setup as control, except NeverAlign fragment is added before cmp.
-# Expected effect:
-# 1. NeverAlign pads cmp+jcc by one byte since cmp and jcc are split by a 64B
-# alignment boundary,
-# 2. This extra byte forces jcc relaxation to a longer format (Control rule #4),
-# 3. This results in an cmp relaxation (Control rule #5),
-# 4. Which in turn makes NeverAlign fragment unnecessary as cmp and jcc
-# are no longer split by an alignment boundary (cmp crosses the boundary).
-# 5. NeverAlign padding is removed.
-# 6. cmp and jcc instruction remain in relaxed form.
-# 7. Relaxation converges, layout succeeds.
-.p2align 6
-# CHECK: 240: int3
-.fill 2, 1, 0xcc
-.L20:
-.nops 122
- int3
-# CHECK: 2bc: int3
-.avoid_end_align 64
-# CHECK-NOT: nop
- cmp $(.L22-.L21), %eax
-# CHECK-NEXT: 2bd: cmpl
-.L21:
- je .L20
-# CHECK-NEXT: 2c3: je
-.nops 125
-.L22:
-
-###############################################################################
-# Experiment B: similar to exp A, but we check that once NeverAlign padding is
-# removed from the layout (exp A, experiment step 5), the increased distance
-# between the symbols L33 and L34 triggers the relaxation of instruction at
-# label L32.
-#
-# Control 1: using a one-byte instruction at L33 (site of NeverAlign) leads to
-# steps 2-3 of exp A, experiment:
-# 2. This extra byte forces jcc relaxation to a longer format (Control rule #4),
-# 3. This results in an cmp relaxation (Control rule #5),
-# => short cmp under L32
-.p2align 6
-# CHECK: 380: int3
-.fill 2, 1, 0xcc
-.L30:
-.nops 122
- int3
-# CHECK: 3fc: int3
- hlt
-#.avoid_end_align 64
-.L33:
- cmp $(.L32-.L31), %eax
-# CHECK: 3fe: cmpl
-.L31:
- je .L30
-# CHECK-NEXT: 404: je
-.nops 114
-.p2align 1
- int3
- int3
-# CHECK: 47c: int3
-.L34:
-.nops 9
-.L32:
- cmp $(.L33-.L34), %eax
-# CHECK: 487: cmp
-# note that the size of cmp is 48a-487 == 3 bytes (distance is exactly -128)
- int3
-# CHECK-NEXT: 48a: int3
-
-# Control 2: leaving out a byte at L43 (site of NeverAlign), plus
-# relaxed jcc and cmp leads to a relaxed cmp under L42 (-129 as cmp's immediate)
-.p2align 6
-# CHECK: 4c0: int3
-.fill 2, 1, 0xcc
-.L40:
-.nops 122
- int3
-# CHECK: 53c: int3
-# int3
-#.avoid_end_align 64
-.L43:
- cmp $(.L42-.L41+0x100), %eax
-# CHECK: 53d: cmpl
-.L41:
- je .L40+0x100
-# CHECK-NEXT: 543: je
-.nops 114
-.p2align 1
- int3
- int3
-# CHECK: 5bc: int3
-.L44:
-.nops 9
-.L42:
- cmp $(.L43-.L44), %eax
-# CHECK: 5c7: cmp
-# note that the size of cmp is 5cd-5c7 == 6 bytes (distance is exactly -129)
- int3
-# CHECK-NEXT: 5cd: int3
-
-# Experiment
-# Checking if removing NeverAlign padding at L53 as a result of alignment and
-# relaxation of cmp and jcc following it (see exp A), thus reproducing the case
-# in Control 2 (getting a relaxed cmp under L52), is handled correctly.
-.p2align 6
-# CHECK: 600: int3
-.fill 2, 1, 0xcc
-.L50:
-.nops 122
- int3
-# CHECK: 67c: int3
-.avoid_end_align 64
-.L53:
-# CHECK-NOT: nop
- cmp $(.L52-.L51), %eax
-# CHECK-NEXT: 67d: cmpl
-.L51:
- je .L50
-# CHECK-NEXT: 683: je
-.nops 114
-.p2align 1
- int3
- int3
-# CHECK: 6fc: int3
-.L54:
-.nops 9
-.L52:
- cmp $(.L53-.L54), %eax
-# CHECK: 707: cmp
-# note that the size of cmp is 70d-707 == 6 bytes (distance is exactly -129)
- int3
-# CHECK-NEXT: 70d: int3
-
-.ifdef ERR
-# ERR: {{.*}}.s:[[#@LINE+1]]:17: error: unknown token in expression
-.avoid_end_align
-# ERR: {{.*}}.s:[[#@LINE+1]]:18: error: expected absolute expression
-.avoid_end_align x
-# ERR: {{.*}}.s:[[#@LINE+1]]:18: error: expected a positive alignment
-.avoid_end_align 0
-# ERR: {{.*}}.s:[[#@LINE+1]]:20: error: unexpected token in directive
-.avoid_end_align 64, 0
-.endif
projects / platform / upstream / llvm.git / commitdiff