Incorrect ELF file for mips64el

[jacob-carlborg]

If I compile for the mips64el architecture LDC creates an incorrect, 32 bit, ELF file:

$ ldc2 main.d -c --mtriple mips64-linux
$ file main.o                                                                                                                                                                                                                                                                                        
main.o: ELF 32-bit MSB relocatable, MIPS, N32 MIPS64 version 1 (GNU/Linux), not stripped
$ ldc2 --version
LDC - the LLVM D compiler (1.39.0):
  based on DMD v2.109.1 and LLVM 17.0.6
  built with LDC - the LLVM D compiler (1.39.0)
  Default target: arm64-apple-darwin24.0.0
  Host CPU: apple-m1
  http://dlang.org - http://wiki.dlang.org/LDC

Using Clang with the same version (more less) of LLVM results in this:

$ clang -target mips64el-linux main.c -o main.o -c
$ file main.o
main.o: ELF 64-bit LSB relocatable, MIPS, MIPS64 rel2 version 1 (SYSV), not stripped
$ clang --version                                                                                                                                                                                                         
clang version 17.0.1
Target: arm64-apple-darwin24.0.0
Thread model: posix

To me it looks like LDC outputs 64 bit MIPS code in a 32 bit ELF file.

[kinke]

MIPS is a bit weird with its ABIs AFAICT; looks like our default is off:

ldc/driver/targetmachine.cpp

Lines 154 to 156 in 48c1dff

	case llvm::Triple::mips64:
	case llvm::Triple::mips64el:
	return "n32";

$ ldc2 -c ../hello.d -mtriple=mips64el-linux -mabi=n64
$ file hello.o 
hello.o: ELF 64-bit LSB relocatable, MIPS, MIPS64 version 1 (GNU/Linux), not stripped

[jacob-carlborg]

I see. Is that intentional?

[JohanEngelen]

I see. Is that intentional?

Don't see anything from history, looks like a typo.

[jacob-carlborg]

Compiling with the -mabi=n64 worked for me. Would it be appropriate to make this the default?

[kinke]

Judging from the clang default, it seems so. Looks like n32 was intended for the 32-bit MIPS targets (which have no default ABI currently), i.e., llvm::Triple::mips[el].