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[XCOFF] Enable -fdata-sections on AIX 

Summary:
Some design decision worth noting about:

I've noticed a recent mailing discussing about why string literal is
not affected by -fdata-sections for ELF target:
http://lists.llvm.org/pipermail/llvm-dev/2020-September/145121.html

But on AIX, our linker could not split the mergeable string like other target.
So I think it would make more sense for us to emit separate csect for
every mergeable string in -fdata-sections mode,
as there might not be other ways for linker to do garbage collection
on unused mergeable string.

Reviewed By: daltenty, hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D88339
This commit is contained in:
jasonliu 2020-10-01 23:35:31 +00:00
parent 61687f3a48
commit 78a9e62aa6
3 changed files with 347 additions and 22 deletions
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50
llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
View File

@ -2055,11 +2055,10 @@ MCSection *TargetLoweringObjectFileWasm::getStaticDtorSection(
MCSymbol *
TargetLoweringObjectFileXCOFF::getTargetSymbol(const GlobalValue *GV,
const TargetMachine &TM) const {
if (TM.getDataSections())
report_fatal_error("XCOFF unique data sections not yet implemented");
// We always use a qualname symbol for a GV that represents
// a declaration, a function descriptor, or a common symbol.
// If a GV represents a GlobalVariable and -fdata-sections is enabled, we
// also return a qualname so that a label symbol could be avoided.
// It is inherently ambiguous when the GO represents the address of a
// function, as the GO could either represent a function descriptor or a
// function entry point. We choose to always return a function descriptor
@ -2074,15 +2073,12 @@ TargetLoweringObjectFileXCOFF::getTargetSymbol(const GlobalValue *GV,
return cast<MCSectionXCOFF>(
getSectionForFunctionDescriptor(cast<Function>(GO), TM))
->getQualNameSymbol();
if (GOKind.isCommon() || GOKind.isBSSLocal())
if (TM.getDataSections() || GOKind.isCommon() || GOKind.isBSSLocal())
return cast<MCSectionXCOFF>(SectionForGlobal(GO, GOKind, TM))
->getQualNameSymbol();
}
// For all other cases, fall back to getSymbol to return the unqualified name.
// This could change for a GV that is a GlobalVariable when we decide to
// support -fdata-sections since we could avoid having label symbols if the
// linkage name is applied to the csect symbol.
return nullptr;
}
@ -2107,9 +2103,6 @@ MCSection *TargetLoweringObjectFileXCOFF::getSectionForExternalReference(
MCSection *TargetLoweringObjectFileXCOFF::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
assert(!TM.getDataSections() &&
"XCOFF unique data sections not yet implemented.");
// Common symbols go into a csect with matching name which will get mapped
// into the .bss section.
if (Kind.isBSSLocal() || Kind.isCommon()) {
@ -2129,6 +2122,9 @@ MCSection *TargetLoweringObjectFileXCOFF::SelectSectionForGlobal(
SmallString<128> Name;
Name = SizeSpec + utostr(Alignment.value());
if (TM.getDataSections())
getNameWithPrefix(Name, GO, TM);
return getContext().getXCOFFSection(Name, XCOFF::XMC_RO, XCOFF::XTY_SD,
Kind, /*BeginSymbolName*/ nullptr);
}
@ -2141,20 +2137,32 @@ MCSection *TargetLoweringObjectFileXCOFF::SelectSectionForGlobal(
return TextSection;
}
if (Kind.isData() || Kind.isReadOnlyWithRel())
// TODO: We may put this under option control, because user may want to
// have read-only data with relocations placed into a read-only section by
// the compiler.
// TODO: We may put Kind.isReadOnlyWithRel() under option control, because
// user may want to have read-only data with relocations placed into a
// read-only section by the compiler.
// For BSS kind, zero initialized data must be emitted to the .data section
// because external linkage control sections that get mapped to the .bss
// section will be linked as tentative defintions, which is only appropriate
// for SectionKind::Common.
if (Kind.isData() || Kind.isReadOnlyWithRel() || Kind.isBSS()) {
if (TM.getDataSections()) {
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
return getContext().getXCOFFSection(Name, XCOFF::XMC_RW, XCOFF::XTY_SD,
SectionKind::getData());
}
return DataSection;
}
// Zero initialized data must be emitted to the .data section because external
// linkage control sections that get mapped to the .bss section will be linked
// as tentative defintions, which is only appropriate for SectionKind::Common.
if (Kind.isBSS())
return DataSection;
if (Kind.isReadOnly())
if (Kind.isReadOnly()) {
if (TM.getDataSections()) {
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
return getContext().getXCOFFSection(Name, XCOFF::XMC_RO, XCOFF::XTY_SD,
SectionKind::getReadOnly());
}
return ReadOnlySection;
}
report_fatal_error("XCOFF other section types not yet implemented.");
}

7
llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
View File

@ -1809,11 +1809,16 @@ void PPCAIXAsmPrinter::emitGlobalVariable(const GlobalVariable *GV) {
MCSymbol *EmittedInitSym = GVSym;
emitLinkage(GV, EmittedInitSym);
emitAlignment(getGVAlignment(GV, DL), GV);
OutStreamer->emitLabel(EmittedInitSym);
// When -fdata-sections is enabled, every GlobalVariable will
// be put into its own csect; therefore, label is not necessary here.
if (!TM.getDataSections())
OutStreamer->emitLabel(EmittedInitSym);
// Emit aliasing label for global variable.
llvm::for_each(GOAliasMap[GV], [this](const GlobalAlias *Alias) {
OutStreamer->emitLabel(getSymbol(Alias));
});
emitGlobalConstant(GV->getParent()->getDataLayout(), GV->getInitializer());
}

312
llvm/test/CodeGen/PowerPC/aix-xcoff-data-sections.ll Normal file
View File

@ -0,0 +1,312 @@
; RUN: llc -verify-machineinstrs -mcpu=pwr4 -mtriple powerpc-ibm-aix-xcoff -data-sections < %s | \
; RUN: FileCheck --check-prefixes=CHECK,CHECK32 %s
; RUN: llc -verify-machineinstrs -mcpu=pwr4 -mtriple powerpc64-ibm-aix-xcoff -data-sections < %s | \
; RUN: FileCheck --check-prefixes=CHECK,CHECK64 %s
; RUN: llc -verify-machineinstrs -mcpu=pwr4 -mtriple powerpc-ibm-aix-xcoff -filetype=obj -data-sections -o %t.o < %s
; RUN: llvm-objdump -D --symbol-description %t.o | FileCheck --check-prefix=CHECKOBJ %s
; RUN: llvm-readobj -syms %t.o | FileCheck --check-prefix=CHECKSYM %s
@ivar = local_unnamed_addr global i32 35, align 4
@const_ivar = constant i32 35, align 4
@a = common global i32 0, align 4
@f = common local_unnamed_addr global i32 0, align 4
@.str = private unnamed_addr constant [9 x i8] c"abcdefgh\00", align 1
@p = global i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str, i32 0, i32 0), align 4
define i8 @foo() {
entry:
%0 = load i8*, i8** @p, align 4
%1 = load i8, i8* %0, align 1
ret i8 %1
}
define i32 @bar() {
entry:
%0 = load i32, i32* @ivar, align 4
%1 = load i32, i32* @const_ivar, align 4
%add = add nsw i32 %0, %1
%2 = load i32, i32* @a, align 4
%add1 = add nsw i32 %add, %2
%3 = load i32, i32* @f, align 4
%add2 = add nsw i32 %add1, %3
ret i32 %add2
}
; CHECK: .csect ivar[RW],2
; CHECK-NEXT: .globl ivar[RW]
; CHECK-NEXT: .align 2
; CHECK-NEXT: .vbyte 4, 35 # 0x23
; CHECK-NEXT: .csect const_ivar[RO],2
; CHECK-NEXT: .globl const_ivar[RO]
; CHECK-NEXT: .align 2
; CHECK-NEXT: .vbyte 4, 35 # 0x23
; CHECK-NEXT: .comm a[RW],4,2
; CHECK-NEXT: .comm f[RW],4,2
; CHECK-NEXT: .csect .rodata.str1.1L...str[RO],2
; CHECK-NEXT: .byte 'a,'b,'c,'d,'e,'f,'g,'h,0000
; CHECK32: .csect p[RW],2
; CHECK32-NEXT: .globl p[RW]
; CHECK32-NEXT: .align 2
; CHECK32-NEXT: .vbyte 4, .rodata.str1.1L...str[RO]
; CHECK64: .csect p[RW],3
; CHECK64-NEXT: .globl p[RW]
; CHECK64-NEXT: .align 3
; CHECK64-NEXT: .vbyte 8, .rodata.str1.1L...str[RO]
; CHECK: .toc
; CHECK-NEXT: L..C0:
; CHECK-NEXT: .tc p[TC],p[RW]
; CHECK-NEXT: L..C1:
; CHECK-NEXT: .tc ivar[TC],ivar[RW]
; CHECK-NEXT: L..C2:
; CHECK-NEXT: .tc a[TC],a[RW]
; CHECK-NEXT: L..C3:
; CHECK-NEXT: .tc f[TC],f[RW]
; CHECKOBJ: 00000038 (idx: 6) const_ivar[RO]:
; CHECKOBJ-NEXT: 38: 00 00 00 23 <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 0000003c (idx: 8) .rodata.str1.1L...str[RO]:
; CHECKOBJ-NEXT: 3c: 61 62 63 64
; CHECKOBJ-NEXT: 40: 65 66 67 68
; CHECKOBJ-NEXT: 44: 00 00 00 00 <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: Disassembly of section .data:
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 00000048 (idx: 10) ivar[RW]:
; CHECKOBJ-NEXT: 48: 00 00 00 23 <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 0000004c (idx: 12) p[RW]:
; CHECKOBJ-NEXT: 4c: 00 00 00 3c <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 00000050 (idx: 14) foo[DS]:
; CHECKOBJ-NEXT: 50: 00 00 00 00 <unknown>
; CHECKOBJ-NEXT: 54: 00 00 00 68 <unknown>
; CHECKOBJ-NEXT: 58: 00 00 00 00 <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 0000005c (idx: 16) bar[DS]:
; CHECKOBJ-NEXT: 5c: 00 00 00 10 <unknown>
; CHECKOBJ-NEXT: 60: 00 00 00 68 <unknown>
; CHECKOBJ-NEXT: 64: 00 00 00 00 <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 00000068 (idx: 20) p[TC]:
; CHECKOBJ-NEXT: 68: 00 00 00 4c <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 0000006c (idx: 22) ivar[TC]:
; CHECKOBJ-NEXT: 6c: 00 00 00 48 <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 00000070 (idx: 24) a[TC]:
; CHECKOBJ-NEXT: 70: 00 00 00 78 <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 00000074 (idx: 26) f[TC]:
; CHECKOBJ-NEXT: 74: 00 00 00 7c <unknown>
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: Disassembly of section .bss:
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 00000078 (idx: 28) a[RW]:
; CHECKOBJ-NEXT: ...
; CHECKOBJ-EMPTY:
; CHECKOBJ-NEXT: 0000007c (idx: 30) f[RW]:
; CHECKOBJ-NEXT: ...
; CHECKSYM: Symbol {
; CHECKSYM: Name: const_ivar
; CHECKSYM: Value (RelocatableAddress): 0x38
; CHECKSYM: Section: .text
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_EXT (0x2)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 4
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_SD (0x1)
; CHECKSYM: StorageMappingClass: XMC_RO (0x1)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: .rodata.str1.1L...str
; CHECKSYM: Value (RelocatableAddress): 0x3C
; CHECKSYM: Section: .text
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_HIDEXT (0x6B)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 9
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_SD (0x1)
; CHECKSYM: StorageMappingClass: XMC_RO (0x1)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: ivar
; CHECKSYM: Value (RelocatableAddress): 0x48
; CHECKSYM: Section: .data
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_EXT (0x2)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 4
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_SD (0x1)
; CHECKSYM: StorageMappingClass: XMC_RW (0x5)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: p
; CHECKSYM: Value (RelocatableAddress): 0x4C
; CHECKSYM: Section: .data
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_EXT (0x2)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 4
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_SD (0x1)
; CHECKSYM: StorageMappingClass: XMC_RW (0x5)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: TOC
; CHECKSYM: Value (RelocatableAddress): 0x68
; CHECKSYM: Section: .data
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_HIDEXT (0x6B)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 0
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_SD (0x1)
; CHECKSYM: StorageMappingClass: XMC_TC0 (0xF)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: p
; CHECKSYM: Value (RelocatableAddress): 0x68
; CHECKSYM: Section: .data
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_HIDEXT (0x6B)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 4
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_SD (0x1)
; CHECKSYM: StorageMappingClass: XMC_TC (0x3)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: ivar
; CHECKSYM: Value (RelocatableAddress): 0x6C
; CHECKSYM: Section: .data
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_HIDEXT (0x6B)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 4
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_SD (0x1)
; CHECKSYM: StorageMappingClass: XMC_TC (0x3)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: a
; CHECKSYM: Value (RelocatableAddress): 0x70
; CHECKSYM: Section: .data
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_HIDEXT (0x6B)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 4
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_SD (0x1)
; CHECKSYM: StorageMappingClass: XMC_TC (0x3)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: f
; CHECKSYM: Value (RelocatableAddress): 0x74
; CHECKSYM: Section: .data
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_HIDEXT (0x6B)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 4
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_SD (0x1)
; CHECKSYM: StorageMappingClass: XMC_TC (0x3)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: a
; CHECKSYM: Value (RelocatableAddress): 0x78
; CHECKSYM: Section: .bss
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_EXT (0x2)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 4
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_CM (0x3)
; CHECKSYM: StorageMappingClass: XMC_RW (0x5)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }
; CHECKSYM: Symbol {
; CHECKSYM: Name: f
; CHECKSYM: Value (RelocatableAddress): 0x7C
; CHECKSYM: Section: .bss
; CHECKSYM: Type: 0x0
; CHECKSYM: StorageClass: C_EXT (0x2)
; CHECKSYM: NumberOfAuxEntries: 1
; CHECKSYM: CSECT Auxiliary Entry {
; CHECKSYM: SectionLen: 4
; CHECKSYM: ParameterHashIndex: 0x0
; CHECKSYM: TypeChkSectNum: 0x0
; CHECKSYM: SymbolAlignmentLog2: 2
; CHECKSYM: SymbolType: XTY_CM (0x3)
; CHECKSYM: StorageMappingClass: XMC_RW (0x5)
; CHECKSYM: StabInfoIndex: 0x0
; CHECKSYM: StabSectNum: 0x0
; CHECKSYM: }
; CHECKSYM: }