clang: how to list supported target architectures?
Currently I am interested in ARM in general and specifically iphone/android targets. But I just want to know more about clang, since it feels to play important role in the years to come.
I tried
clang -cc1 --help|grep -i list
clang -cc1 --help|grep arch|grep -v search
clang -cc1 --help|grep target
-triple <value> Specify target triple (e.g. i686-apple-darwin9)
I know clang has -triplet parameter, but how can I list all possible values for it? I found that clang is very different to gcc in respect to cross compiling, in GCC world you should have separate binary for everything, like PLATFORM_make or PLATFORM_ld (i*86-pc-cygwin i*86-*-linux-gnu etc. http://git.savannah.gnu.org/cgit/libtool.git/tree/doc/PLATFORMS)
in clang world, it's only one binary (as I read on some forums). But how do I get the list of supported targets? And if my target it not supported on my distro(linux/windows/macos/whatever) how can I get the one that supports more platform?
if I SVN latest clang like this:
svn co http://llvm.org/svn/llvm-project/cfe/trunk clang
will I get most of platforms? It looks like Clang was not built with cross compiling in mind right away, but since it's llvm based it should be very cross-friendly in theory? thank you!
So far as I can tell, there is no command-line option to list which architectures a given clang binary supports, and even running strings on it doesn't really help. Clang is essentially just a C to LLVM translator, and it's LLVM itself that deals with the nitty-gritty of generating actual machine code, so it's not entirely surprising that Clang isn't paying much attention to the underlying architecture.
As others have already noted, you can ask llc which architectures it supports. This isn't all that helpful not just because these LLVM components might not be installed, but because of the vagaries of search paths and packaging systems, your llc and clang binaries may not correspond to the same version of LLVM.
However, for the sake of argument, let's say that you compiled both LLVM and Clang yourself or that you're otherwise happy to accept your LLVM binaries as good enough:
-
llc --versionwill give a list of all architectures it supports. By default, it is compiled to support all architectures. What you may think of as a single architecture such as ARM may have several LLVM architectures such as regular ARM, Thumb and AArch64. This is mainly for implementation convenience because the different execution modes have very different instruction encodings and semantics. - For each of the architectures listed,
llc -march=ARCH -mattr=helpwill list "available CPUs" and "available features". The CPUs are generally just a convenient way of setting a default collection of features.
But now for the bad news. There is no convenient table of triples in Clang or LLVM that can be dumped, because the architecture-specific backends have the option of parsing the triple string into an llvm::Triple object (defined in include/llvm/ADT/Triple.h). In other words, to dump all available triples requires solving the Halting Problem. See, for example, llvm::ARM_MC::ParseARMTriple(...) which special-cases parsing the string "generic".
Ultimately, though, the "triple" is mostly a backwards-compatibility feature to make Clang a drop-in replacement for GCC, so you generally don't need to pay much attention to it unless you are porting Clang or LLVM to a new platform or architecture. Instead, you will probably find the output of llc -march=arm -mattr=help and boggling at the huge array of different ARM features to be more useful in your investigations.
Good luck with your research!
I am using Clang 3.3, I think the best way to get the answer is reading the source code. in llvm/ADT/Triple.h (http://llvm.org/doxygen/Triple_8h_source.html):
enum ArchType {
UnknownArch,
arm, // ARM: arm, armv.*, xscale
aarch64, // AArch64: aarch64
hexagon, // Hexagon: hexagon
mips, // MIPS: mips, mipsallegrex
mipsel, // MIPSEL: mipsel, mipsallegrexel
mips64, // MIPS64: mips64
mips64el,// MIPS64EL: mips64el
msp430, // MSP430: msp430
ppc, // PPC: powerpc
ppc64, // PPC64: powerpc64, ppu
r600, // R600: AMD GPUs HD2XXX - HD6XXX
sparc, // Sparc: sparc
sparcv9, // Sparcv9: Sparcv9
systemz, // SystemZ: s390x
tce, // TCE (http://tce.cs.tut.fi/): tce
thumb, // Thumb: thumb, thumbv.*
x86, // X86: i[3-9]86
x86_64, // X86-64: amd64, x86_64
xcore, // XCore: xcore
mblaze, // MBlaze: mblaze
nvptx, // NVPTX: 32-bit
nvptx64, // NVPTX: 64-bit
le32, // le32: generic little-endian 32-bit CPU (PNaCl / Emscripten)
amdil, // amdil: amd IL
spir, // SPIR: standard portable IR for OpenCL 32-bit version
spir64 // SPIR: standard portable IR for OpenCL 64-bit version
};
and in clang/lib/Driver/ToolChains.cpp , there is sth about arm.
static const char *GetArmArchForMArch(StringRef Value) {
return llvm::StringSwitch<const char*>(Value)
.Case("armv6k", "armv6")
.Case("armv6m", "armv6m")
.Case("armv5tej", "armv5")
.Case("xscale", "xscale")
.Case("armv4t", "armv4t")
.Case("armv7", "armv7")
.Cases("armv7a", "armv7-a", "armv7")
.Cases("armv7r", "armv7-r", "armv7")
.Cases("armv7em", "armv7e-m", "armv7em")
.Cases("armv7f", "armv7-f", "armv7f")
.Cases("armv7k", "armv7-k", "armv7k")
.Cases("armv7m", "armv7-m", "armv7m")
.Cases("armv7s", "armv7-s", "armv7s")
.Default(0);
}
static const char *GetArmArchForMCpu(StringRef Value) {
return llvm::StringSwitch<const char *>(Value)
.Cases("arm9e", "arm946e-s", "arm966e-s", "arm968e-s", "arm926ej-s","armv5")
.Cases("arm10e", "arm10tdmi", "armv5")
.Cases("arm1020t", "arm1020e", "arm1022e", "arm1026ej-s", "armv5")
.Case("xscale", "xscale")
.Cases("arm1136j-s", "arm1136jf-s", "arm1176jz-s", "arm1176jzf-s", "armv6")
.Case("cortex-m0", "armv6m")
.Cases("cortex-a8", "cortex-r4", "cortex-a9", "cortex-a15", "armv7")
.Case("cortex-a9-mp", "armv7f")
.Case("cortex-m3", "armv7m")
.Case("cortex-m4", "armv7em")
.Case("swift", "armv7s")
.Default(0);
}
One hint you can do: if you're trying to find a particular target triple, is to install llvm on that system then do a
$ llc --version | grep Default
Default target: x86_64-apple-darwin16.1.0
or alternatively:
$ llvm-config --host-target
x86_64-apple-darwin16.0.0
or
$ clang -v 2>&1 | grep Target
Target: x86_64-apple-darwin16.1.0
Then you know how to target it when cross compiling anyway.
Apparently there are "lots" of targets out there, here's a list, feel free to add to it, community wiki style:
arm-none-eabi
armv7a-none-eabi
arm-linux-gnueabihf
arm-none-linux-gnueabi
i386-pc-linux-gnu
x86_64-apple-darwin10
i686-w64-windows-gnu # same as i686-w64-mingw32
x86_64-pc-linux-gnu # from ubuntu 64 bit
x86_64-unknown-windows-cygnus # cygwin 64-bit
x86_64-w64-windows-gnu # same as x86_64-w64-mingw32
i686-pc-windows-gnu # MSVC
x86_64-pc-windows-gnu # MSVC 64-BIT
Here's what the docs list anyway (apparently it's a quadruple [or quintuple?] instead of a triple these days):
The triple has the general format <arch><sub>-<vendor>-<sys>-<abi>, where:
arch = x86, arm, thumb, mips, etc.
sub = for ex. on ARM: v5, v6m, v7a, v7m, etc.
vendor = pc, apple, nvidia, ibm, etc.
sys = none, linux, win32, darwin, cuda, etc.
abi = eabi, gnu, android, macho, elf, etc.
and you can even fine tune specify a target cpu beyond this, though it uses a sensible default for the target cpu based on the triple.
Sometimes targets "resolve" to the same thing, so to see what a target is actually treated as:
$ clang -target x86_64-w64-mingw32 -v 2>&1 | grep Target
Target: x86_64-w64-windows-gnu
Starting Clang 11 (trunk), the list of supported target architectures could be handily printed using the newly added -print-targets flag:
$ clang-11 -print-targets
Registered Targets:
aarch64 - AArch64 (little endian)
aarch64_32 - AArch64 (little endian ILP32)
aarch64_be - AArch64 (big endian)
amdgcn - AMD GCN GPUs
arm - ARM
arm64 - ARM64 (little endian)
arm64_32 - ARM64 (little endian ILP32)
armeb - ARM (big endian)
avr - Atmel AVR Microcontroller
bpf - BPF (host endian)
bpfeb - BPF (big endian)
bpfel - BPF (little endian)
hexagon - Hexagon
lanai - Lanai
mips - MIPS (32-bit big endian)
mips64 - MIPS (64-bit big endian)
mips64el - MIPS (64-bit little endian)
mipsel - MIPS (32-bit little endian)
msp430 - MSP430 [experimental]
nvptx - NVIDIA PTX 32-bit
nvptx64 - NVIDIA PTX 64-bit
ppc32 - PowerPC 32
ppc64 - PowerPC 64
ppc64le - PowerPC 64 LE
r600 - AMD GPUs HD2XXX-HD6XXX
riscv32 - 32-bit RISC-V
riscv64 - 64-bit RISC-V
sparc - Sparc
sparcel - Sparc LE
sparcv9 - Sparc V9
systemz - SystemZ
thumb - Thumb
thumbeb - Thumb (big endian)
wasm32 - WebAssembly 32-bit
wasm64 - WebAssembly 64-bit
x86 - 32-bit X86: Pentium-Pro and above
x86-64 - 64-bit X86: EM64T and AMD64
xcore - XCore
References: LLVM PR, LLVM commit, Clang 11 documentation.