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[clang] Implement pragma clang section on COFF targets #112714

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Jan 22, 2025
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[clang] Implement pragma clang section on COFF targets #112714

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2 changes: 1 addition & 1 deletion clang/docs/LanguageExtensions.rst
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Expand Up @@ -5548,7 +5548,7 @@ The ``#pragma clang section`` directive obeys the following rules:

* The pragma clang section is enabled automatically, without need of any flags.

* This feature is only defined to work sensibly for ELF and Mach-O targets.
* This feature is only defined to work sensibly for ELF, Mach-O and COFF targets.

* If section name is specified through _attribute_((section("myname"))), then
the attribute name gains precedence.
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2 changes: 2 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -1093,6 +1093,8 @@ Windows Support
When `-fms-compatibility-version=18.00` or prior is set on the command line this Microsoft extension is still
allowed as VS2013 and prior allow it.

- Clang now supports the ``#pragma clang section`` directive for COFF targets.

LoongArch Support
^^^^^^^^^^^^^^^^^

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1 change: 1 addition & 0 deletions clang/test/Sema/pragma-clang-section.c
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@@ -1,4 +1,5 @@
// RUN: %clang_cc1 -fsyntax-only -verify %s -triple arm-none-eabi
// RUN: %clang_cc1 -fsyntax-only -verify %s -triple arm64-windows-msvc
#pragma clang section bss = "mybss.1" data = "mydata.1" rodata = "myrodata.1" text = "mytext.1" // expected-note 2 {{#pragma entered here}}
#pragma clang section bss="" data="" rodata="" text=""
#pragma clang section
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54 changes: 23 additions & 31 deletions llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
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Expand Up @@ -788,29 +788,35 @@ getGlobalObjectInfo(const GlobalObject *GO, const TargetMachine &TM) {
return {Group, IsComdat, Flags};
}

static MCSection *selectExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM,
MCContext &Ctx, Mangler &Mang, unsigned &NextUniqueID,
bool Retain, bool ForceUnique) {
StringRef SectionName = GO->getSection();

static StringRef handlePragmaClangSection(const GlobalObject *GO,
SectionKind Kind) {
// Check if '#pragma clang section' name is applicable.
// Note that pragma directive overrides -ffunction-section, -fdata-section
// and so section name is exactly as user specified and not uniqued.
const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
if (GV && GV->hasImplicitSection()) {
auto Attrs = GV->getAttributes();
if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
SectionName = Attrs.getAttribute("bss-section").getValueAsString();
} else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
} else if (Attrs.hasAttribute("relro-section") && Kind.isReadOnlyWithRel()) {
SectionName = Attrs.getAttribute("relro-section").getValueAsString();
} else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
SectionName = Attrs.getAttribute("data-section").getValueAsString();
}
if (Attrs.hasAttribute("bss-section") && Kind.isBSS())
return Attrs.getAttribute("bss-section").getValueAsString();
else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly())
return Attrs.getAttribute("rodata-section").getValueAsString();
else if (Attrs.hasAttribute("relro-section") && Kind.isReadOnlyWithRel())
return Attrs.getAttribute("relro-section").getValueAsString();
else if (Attrs.hasAttribute("data-section") && Kind.isData())
return Attrs.getAttribute("data-section").getValueAsString();
}

return GO->getSection();
}

static MCSection *selectExplicitSectionGlobal(const GlobalObject *GO,
SectionKind Kind,
const TargetMachine &TM,
MCContext &Ctx, Mangler &Mang,
unsigned &NextUniqueID,
bool Retain, bool ForceUnique) {
StringRef SectionName = handlePragmaClangSection(GO, Kind);

// Infer section flags from the section name if we can.
Kind = getELFKindForNamedSection(SectionName, Kind);

Expand Down Expand Up @@ -1291,21 +1297,7 @@ static void checkMachOComdat(const GlobalValue *GV) {
MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {

StringRef SectionName = GO->getSection();

const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
if (GV && GV->hasImplicitSection()) {
auto Attrs = GV->getAttributes();
if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
SectionName = Attrs.getAttribute("bss-section").getValueAsString();
} else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
} else if (Attrs.hasAttribute("relro-section") && Kind.isReadOnlyWithRel()) {
SectionName = Attrs.getAttribute("relro-section").getValueAsString();
} else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
SectionName = Attrs.getAttribute("data-section").getValueAsString();
}
}
StringRef SectionName = handlePragmaClangSection(GO, Kind);

// Parse the section specifier and create it if valid.
StringRef Segment, Section;
Expand Down Expand Up @@ -1674,7 +1666,7 @@ static int getSelectionForCOFF(const GlobalValue *GV) {

MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
StringRef Name = GO->getSection();
StringRef Name = handlePragmaClangSection(GO, Kind);
if (Name == getInstrProfSectionName(IPSK_covmap, Triple::COFF,
/*AddSegmentInfo=*/false) ||
Name == getInstrProfSectionName(IPSK_covfun, Triple::COFF,
Expand Down
146 changes: 146 additions & 0 deletions llvm/test/CodeGen/X86/clang-section-coff.ll
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@@ -0,0 +1,146 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
;RUN: llc -mtriple=x86_64-windows-msvc %s -o - | FileCheck %s
;Test that global variables and functions are assigned to correct sections.

@a = global i32 0, align 4 #0
@b = global i32 1, align 4 #0
@c = global [4 x i32] zeroinitializer, align 4 #0
@d = global [5 x i16] zeroinitializer, align 2 #0
@e = global [6 x i16] [i16 0, i16 0, i16 1, i16 0, i16 0, i16 0], align 2 #0
@f = constant i32 2, align 4 #0
@h = global i32 0, align 4 #1
@i = global i32 0, align 4 #2
@j = constant i32 4, align 4 #2
@k = global i32 0, align 4 #2
@_ZZ3gooE7lstat_h = internal global i32 0, align 4 #2
@_ZL1g = internal global [2 x i32] zeroinitializer, align 4 #0
@l = global i32 5, align 4 #3
@m = constant i32 6, align 4 #3
@n = global i32 0, align 4
@o = global i32 6, align 4
@p = constant i32 7, align 4

declare i32 @zoo(ptr, ptr) #6

; Function Attrs: noinline nounwind
define i32 @hoo() #7 {
; CHECK-LABEL: hoo:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: movl b(%rip), %eax
; CHECK-NEXT: retq
entry:
%0 = load i32, ptr @b, align 4
ret i32 %0
}

attributes #0 = { "bss-section"="my_bss.1" "data-section"="my_data.1" "rodata-section"="my_rodata.1" }
attributes #1 = { "data-section"="my_data.1" "rodata-section"="my_rodata.1" }
attributes #2 = { "bss-section"="my_bss.2" "rodata-section"="my_rodata.1" }
attributes #3 = { "bss-section"="my_bss.2" "data-section"="my_data.2" "rodata-section"="my_rodata.2" }
attributes #6 = { "correctly-rounded-divide-sqrt-fp-math"="false" "denormal-fp-math"="preserve-sign,preserve-sign" "disable-tail-calls"="false" "less-precise-fpmad"="false" "frame-pointer"="none" "no-infs-fp-math"="true" "no-nans-fp-math"="true" "no-signed-zeros-fp-math"="true" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #7 = { noinline nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "denormal-fp-math"="preserve-sign,preserve-sign" "disable-tail-calls"="false" "less-precise-fpmad"="false" "frame-pointer"="none" "no-infs-fp-math"="true" "no-jump-tables"="false" "no-nans-fp-math"="true" "no-signed-zeros-fp-math"="true" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }

!llvm.module.flags = !{!0, !1, !2, !3}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{i32 1, !"static_rwdata", i32 1}
!2 = !{i32 1, !"enumsize_buildattr", i32 2}
!3 = !{i32 1, !"armlib_unavailable", i32 0}

;CHECK: .section my_bss.1,"bw"
;CHECK: .globl a # @a
;CHECK: .p2align 2, 0x0
;CHECK: a:
;CHECK: .long 0 # 0x0

;CHECK: .section my_data.1,"dw"
;CHECK: .globl b # @b
;CHECK: .p2align 2, 0x0
;CHECK: b:
;CHECK: .long 1 # 0x1

;CHECK: .section my_bss.1,"bw"
;CHECK: .globl c # @c
;CHECK: .p2align 2, 0x0
;CHECK: c:
;CHECK: .zero 16
;CHECK: .globl d # @d
;CHECK: .p2align 1, 0x0
;CHECK: d:
;CHECK: .zero 10

;CHECK: .section my_data.1,"dw"
;CHECK: .globl e # @e
;CHECK: .p2align 1, 0x0
;CHECK: e:
;CHECK: .short 0 # 0x0
;CHECK: .short 0 # 0x0
;CHECK: .short 1 # 0x1
;CHECK: .short 0 # 0x0
;CHECK: .short 0 # 0x0
;CHECK: .short 0 # 0x0

;CHECK: .section my_rodata.1,"dr"
;CHECK: .globl f # @f
;CHECK: .p2align 2, 0x0
;CHECK: f:
;CHECK: .long 2 # 0x2
;CHECK: .bss
;CHECK: .globl h # @h
;CHECK: .p2align 2, 0x0
;CHECK: h:
;CHECK: .long 0 # 0x0

;CHECK: .section my_bss.2,"bw"
;CHECK: .globl i # @i
;CHECK: .p2align 2, 0x0
;CHECK: i:
;CHECK: .long 0 # 0x0

;CHECK: .section my_rodata.1,"dr"
;CHECK: .globl j # @j
;CHECK: .p2align 2, 0x0
;CHECK: j:
;CHECK: .long 4 # 0x4

;CHECK: .section my_bss.2,"bw"
;CHECK: .globl k # @k
;CHECK: .p2align 2, 0x0
;CHECK: k:
;CHECK: .long 0 # 0x0
;CHECK: .p2align 2, 0x0 # @_ZZ3gooE7lstat_h
;CHECK: _ZZ3gooE7lstat_h:
;CHECK: .long 0 # 0x0

;CHECK: .section my_bss.1,"bw"
;CHECK: .p2align 2, 0x0 # @_ZL1g
;CHECK: _ZL1g:
;CHECK: .zero 8

;CHECK: .section my_data.2,"dw"
;CHECK: .globl l # @l
;CHECK: .p2align 2, 0x0
;CHECK: l:
;CHECK: .long 5 # 0x5

;CHECK: .section my_rodata.2,"dr"
;CHECK: .globl m # @m
;CHECK: .p2align 2, 0x0
;CHECK: m:
;CHECK: .long 6 # 0x6
;CHECK: .bss
;CHECK: .globl n # @n
;CHECK: .p2align 2, 0x0
;CHECK: n:
;CHECK: .long 0 # 0x0
;CHECK: .data
;CHECK: .globl o # @o
;CHECK: .p2align 2, 0x0
;CHECK: o:
;CHECK: .long 6 # 0x6

;CHECK: .section .rdata,"dr"
;CHECK: .globl p # @p
;CHECK: .p2align 2, 0x0
;CHECK: p:
;CHECK: .long 7 # 0x7
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