# Compiling LLVM with visual studio

Here at Phasetw0 we hate monolitic compilers. Thats why we exclusively use the llvm compiler infrastructure as our build toolchain.
Written by 11philip22.

Install cmake.
Install both clang extensions in Visual Studio.

Make sure python3.6+ is installed.

Install the psutil python module

pip install psutil

Open the Visual Studio developer console and use the commands bellow to generate a visual studio solution to compile llvm.
Please also checkout all availbe cmake flags at: https://llvm.org/docs/CMake.html#options-and-variables.

git clone https://github.com/llvm/llvm-project.git llvm
cd llvm
cmake -S llvm -B build -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_USE_LINKER=lld -DLLVM_TARGETS_TO_BUILD=X86 -DCMAKE_INSTALL_PREFIX="C:\llvm" -Thost=x64

This creates the Visual Studio solution in ./llvm/build.

Since compilation will take a really long time i suggest to set the solution's configuration to Release.
Now build the ALL_BUILD project to compile llvm.

Run the INSTALL project to install llvm to C:\llvm

First we create a new Visual Studio project with the name llvmTest.
Create a HelloWorld.c source file with the following contents:

#include <stdio.h>
#include <string.h>

char str1[20] = "I love ";
char str2[12] = "11philip22\n";

int main() {
	int x = 1;
	int y = 2;
	printf("hello world %d\n", (x + y) * (x + y));
	char* newStr = _strdup(str1);
	strcat_s(newStr, 20, str2);
	printf("%s", newStr);

	return 0;
}

In the project property page set Platform Toolset to LLVM (clang-cl).

<Project>
  <PropertyGroup>
    <LLVMInstallDir>C:\llvm</LLVMInstallDir>
	<LLVMToolsVersion>14.0.0</LLVMToolsVersion>
  </PropertyGroup>
</Project>

Now Build and Run the project like you would usually do in visual studio.

• https://llvm.org/docs/GettingStartedVS.html
• https://llvm.org/docs/CMake.html
• https://docs.microsoft.com/en-us/cpp/build/clang-support-msbuild?view=msvc-160