I’m trying to build LLVM on Windows 10 for x86_64. The cmake cmdline I used is

c:\cmake-3.8.0-rc1-win64-x64\bin\cmake.exe -DLLVM_TARGETS_TO_BUILD=x86_64 -G “Visual Studio 14” .

And this ultimately gives me:

llvm-build: error: invalid target to enable: ‘x86_64’ (not in project)

The source I’m trying to build is the llvm-3.8.0.src.tar.xz I got from http://releases.llvm.org/download.html

If I don’t specify LLVM_TARGETS_TO_BUILD or I set it to “X86”, cmake completes fine, and I can build the solution (but it gives me 32-bit binaries)

What am I doing wrong?


Hi John,

If I don't specify LLVM_TARGETS_TO_BUILD or I set it to "X86", cmake
completes fine, and I can build the solution

X86 is definitely what you should be using (both 32-bit and 64-bit x86
backends share the code in lib/Target/X86, which is the key point
CMake is looking for).

(but it gives me 32-bit binaries)

I assume this means that when you run the Clang you've just built it
defaults to producing 32-bit binaries? If so, on *NIX platforms you
override the default target with LLVM_DEFAULT_TARGET_TRIPLE.

I'm not *sure* that'll work on Windows (which has its own weird driver
on top of Clang), but as far as I can tell from here it behaves as I'd
expect. If so you want to set it to something like
"x86_64-pc-windows-msvc18.0.0" for 64-bit default.

clang-cl also seems to accept -m32 and -m64 options as overrides,
which may or may not be useful to you. Probably a bit hacky to put
into a build system since MSVC itself won't accept them.



Hi John,

[Adding llvm-dev again; best to keep these things in the open so they
show up in future searches].

After building the solution cmake gave me (with X86), I got those libraries
I wanted, but they appear to be 32-bit. I need 64-bit versions.

Ah, that was my second guess. My limited reading suggests that Windows
has completely separate compilers to produce x64 and x32
libraries/binaries. A bit of grubbing around the internet suggests
CMake exposes this with the CMAKE_GENERATOR_PLATFORM variable, and -A
on the command line. So I'd suggest:

-DLLVM_TARGETS_TO_BUILD=x86_64 -G "Visual Studio 14" -A Win64

(plus a path to the source). That last argument is a bit of a guess,
but fits in with documentation at
(for example).

Hope this works out for you.


Thanks! That should get me on the right track.

Direct reply was accidental. Thanks for putting me back on the list :slight_smile:

I’ll repost with details once I’ve got it working.

Available targets should be found at

And CMake for Windows should have

The following generators are available on this platform:
Visual Studio 14 2015 [arch] = Generates Visual Studio 2015 project files.
Optional [arch] can be “Win64” or “ARM”.

So I’d suggest:
cmake -DLLVM_TARGETS_TO_BUILD=x86 -G “Visual Studio 14 2015 Win64”


cmake -DLLVM_TARGETS_TO_BUILD=X86 -G “Visual Studio 14 2015 Win64”
capital ‘X’ to be pedantic. ^

Appending “Win64” to Visual Studio generator name did the trick! Thanks, guys.