[X86] Clang option -fuse-init-array has no effect when generating for MCU target

[AndreiGrischenko]

Summary

Our runtime for MCU X86 target supports .init_array section for globals that should be dynamically initialized.
But default Clang generates .ctors section and even if it has option -fuse-init-array, the option has no effect if set explicitly in a command-line.
The problem is in lack of -fuse-array-init option initialization in CodeGen

void
X86LinuxNaClTargetObjectFile::Initialize(MCContext &Ctx,

                                       const TargetMachine &TM) {
TargetLoweringObjectFileELF::Initialize(Ctx, TM);
InitializeELF(TM.Options.UseInitArray);

}

[ahatanak]

Do you need a front-end test? Since the changes are in the backend, I think it's better to add the test to the backend (using llc).

[AndreiGrischenko]

In D32543#738595, @ahatanak wrote:

Do you need a front-end test? Since the changes are in the backend, I think it's better to add the test to the backend (using llc).

Yes, changes are in the backend, but they fix interface between frontend and backend, that's why I need to check option -fuse-init-array using front-end. Using llc I cannot check these changes.

[craig.topper]

Should we add a test to test/CodeGen/X86/constructor.ll that test appears to have been modified when NAcl was added to the line you changed.

[craig.topper]

It looksl ike UseInitArray is connected to -use-ctors command line option to llc so we should be able to test this without a frontend test.

[AndreiGrischenko]

Thanks Craig for the good advice. You are right I can check llc with MCU triple using option -use-ctors. Please see updated patch.

[craig.topper]

LGTM

llvm/trunk/lib/Target/X86/X86TargetMachine.cpp

static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
   if (TT.isOSBinFormatMachO()) {
     if (TT.getArch() == Triple::x86_64)
       return llvm::make_unique<X86_64MachoTargetObjectFile>();
     return llvm::make_unique<TargetLoweringObjectFileMachO>();
   }
 
   if (TT.isOSFreeBSD())
     return llvm::make_unique<X86FreeBSDTargetObjectFile>();
-  if (TT.isOSLinux() || TT.isOSNaCl())
+  if (TT.isOSLinux() || TT.isOSNaCl() || TT.isOSIAMCU())
     return llvm::make_unique<X86LinuxNaClTargetObjectFile>();
   if (TT.isOSFuchsia())
     return llvm::make_unique<X86FuchsiaTargetObjectFile>();
   if (TT.isOSBinFormatELF())
     return llvm::make_unique<X86ELFTargetObjectFile>();
   if (TT.isKnownWindowsMSVCEnvironment() || TT.isWindowsCoreCLREnvironment())
     return llvm::make_unique<X86WindowsTargetObjectFile>();
   if (TT.isOSBinFormatCOFF())

llvm/trunk/test/CodeGen/X86/constructor.ll

 ; RUN: llc -mtriple x86_64-pc-linux -use-ctors < %s | FileCheck --check-prefix=CTOR %s
 ; RUN: llc -mtriple x86_64-unknown-freebsd -use-ctors < %s | FileCheck --check-prefix=CTOR %s
 ; RUN: llc -mtriple x86_64-pc-linux < %s | FileCheck --check-prefix=INIT-ARRAY %s
 ; RUN: llc -mtriple x86_64-unknown-freebsd < %s | FileCheck --check-prefix=INIT-ARRAY %s
 ; RUN: llc -mtriple x86_64-unknown-nacl < %s | FileCheck --check-prefix=NACL %s
+; RUN: llc -mtriple i586-intel-elfiamcu -use-ctors < %s | FileCheck %s --check-prefix=MCU-CTORS
+; RUN: llc -mtriple i586-intel-elfiamcu < %s | FileCheck %s --check-prefix=MCU-INIT-ARRAY
 @llvm.global_ctors = appending global [2 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @f, i8* null}, { i32, void ()*, i8* } { i32 15, void ()* @g, i8* @v }]
 
 @v = weak_odr global i8 0
 
 define void @f() {
 entry:
   ret void
 }

 ; INIT-ARRAY-NEXT:  .quad f
 
 ; NACL:   .section  .init_array.15,"aGw",@init_array,v,comdat
 ; NACL-NEXT:  .p2align  2
 ; NACL-NEXT:  .long g
 ; NACL-NEXT:  .section  .init_array,"aw",@init_array
 ; NACL-NEXT:  .p2align  2
 ; NACL-NEXT:  .long f
+
+; MCU-CTORS:         .section        .ctors,"aw",@progbits
+; MCU-INIT-ARRAY:    .section        .init_array,"aw",@init_array