In the Vulkan SDK there are two different tools that allow to compile HLSL to SPIR-V: dxc and glslangValidator.
Why do we need two? What are the differences? How do I decide which one to use?
For HLSL shaders you should use DXC. DXC is Microsoft's official shader compiler and it's support for HLSL is far more complete than the one in glslangValidator. glslangValidator is mainly used for GLSL and has very limited HLSL support.