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Expose function sections option #28088

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Merged
merged 2 commits into from
Jan 13, 2020
Merged

Expose function sections option #28088

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439d0ca
Expose separate function sections option to compiler
asuhan Sep 19, 2019
1de737f
Add function sections test
asuhan Oct 5, 2019
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5 changes: 4 additions & 1 deletion include/swift/AST/IRGenOptions.h
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Expand Up @@ -146,6 +146,9 @@ class IRGenOptions {
/// objects.
unsigned EmitStackPromotionChecks : 1;

/// Emit functions to separate sections.
unsigned FunctionSections : 1;

/// The maximum number of bytes used on a stack frame for stack promotion
/// (includes alloc_stack allocations).
unsigned StackPromotionSizeLimit = 1024;
Expand Down Expand Up @@ -249,7 +252,7 @@ class IRGenOptions {
IntegratedREPL(false), DisableLLVMOptzns(false),
DisableSwiftSpecificLLVMOptzns(false), DisableLLVMSLPVectorizer(false),
DisableFPElim(true), Playground(false), EmitStackPromotionChecks(false),
PrintInlineTree(false), EmbedMode(IRGenEmbedMode::None),
FunctionSections(false), PrintInlineTree(false), EmbedMode(IRGenEmbedMode::None),
HasValueNamesSetting(false), ValueNames(false),
EnableReflectionMetadata(true), EnableReflectionNames(true),
EnableAnonymousContextMangledNames(false), ForcePublicLinkage(false),
Expand Down
4 changes: 4 additions & 0 deletions include/swift/Option/FrontendOptions.td
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Expand Up @@ -334,6 +334,10 @@ def disable_reflection_names : Flag<["-"], "disable-reflection-names">,
HelpText<"Disable emission of names of stored properties and enum cases in"
"reflection metadata">;

def function_sections: Flag<["-"], "function-sections">,
Flags<[FrontendOption, NoInteractiveOption]>,
HelpText<"Emit functions to separate sections.">;

def stack_promotion_checks : Flag<["-"], "emit-stack-promotion-checks">,
HelpText<"Emit runtime checks for correct stack promotion of objects.">;

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2 changes: 2 additions & 0 deletions lib/Frontend/CompilerInvocation.cpp
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Expand Up @@ -1136,6 +1136,8 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
Opts.StackPromotionSizeLimit = limit;
}

Opts.FunctionSections = Args.hasArg(OPT_function_sections);

if (Args.hasArg(OPT_autolink_force_load))
Opts.ForceLoadSymbolName = Args.getLastArgValue(OPT_module_link_name);

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1 change: 1 addition & 0 deletions lib/IRGen/IRGen.cpp
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Expand Up @@ -162,6 +162,7 @@ swift::getIRTargetOptions(IRGenOptions &Opts, ASTContext &Ctx) {
// Explicitly request debugger tuning for LLDB which is the default
// on Darwin platforms but not on others.
TargetOpts.DebuggerTuning = llvm::DebuggerKind::LLDB;
TargetOpts.FunctionSections = Opts.FunctionSections;

auto *Clang = static_cast<ClangImporter *>(Ctx.getClangModuleLoader());
clang::TargetOptions &ClangOpts = Clang->getTargetInfo().getTargetOpts();
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5 changes: 5 additions & 0 deletions test/LinkerSections/Inputs/FunctionSections.swift
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@@ -0,0 +1,5 @@
public typealias Void = ()

public func func1() -> Void {}

public func func2() -> Void {}
3 changes: 3 additions & 0 deletions test/LinkerSections/Inputs/FunctionSectionsUse.swift
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@@ -0,0 +1,3 @@
import FunctionSections

func1()
10 changes: 10 additions & 0 deletions test/LinkerSections/function_sections.swift
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@@ -0,0 +1,10 @@
// REQUIRES: OS=linux-gnu || OS=linux-androideabi || OS=linux-android || OS=freebsd
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Can we use %target-object-format and compare it to ELF instead?

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Not in the REQUIRES directive:

ValueError: couldn't parse text: '%target-object-format=elf'
in expression: '%target-object-format=elf'
in REQUIRES: directive on test line 1

If there is another way to limit it to ELF, that'd be cool.

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That is rather unfortunate. Out of curiosity, what happens if you use -function-sections on MachO or PE/COFF? I'm wondering if we should actually prevent that in the driver. Apple's usage of MachO actually uses .subsections_via_symbols which means that everything is atomized and you effectively are doing -function-sections, and PE/COFF's symbol resolution is pretty close to this already.

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I don't have easy access to the other platforms. Also, is the linker / the map file format the same, at this point?

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The linker map is linker dependent unfortunately.

// RUN: %empty-directory(%t)
// RUN: %target-build-swift -Xfrontend -function-sections -emit-module -emit-library -static -parse-stdlib %S/Inputs/FunctionSections.swift
// RUN: %target-build-swift -Xlinker --gc-sections -Xlinker -Map=%t/../../FunctionSections.map -I%t/../.. -L%t/../.. -lFunctionSections %S/Inputs/FunctionSectionsUse.swift
// RUN: %FileCheck %s < %t/../../FunctionSections.map

// CHECK: Discarded input sections
// CHECK: .text.$s16FunctionSections5func2yyF
// CHECK: Memory map
// CHECK: .text.$s16FunctionSections5func1yyF
12 changes: 12 additions & 0 deletions test/LinkerSections/function_sections_ir_check.swift
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@@ -0,0 +1,12 @@
// RUN: %empty-directory(%t)
// RUN: %target-build-swift -Xfrontend -function-sections -emit-library -emit-ir -static -parse-stdlib %S/Inputs/FunctionSections.swift | %FileCheck %s

// CHECK: define {{(dllexport |protected )?}}swiftcc void @"$s16FunctionSections5func1yyF"() #0 {
// CHECK: entry:
// CHECK: ret void
// CHECK: }

// CHECK: define {{(dllexport |protected )?}}swiftcc void @"$s16FunctionSections5func2yyF"() #0 {
// CHECK: entry:
// CHECK: ret void
// CHECK: }