[llvm] [llvm][docs] Note Windows on Arm setting in Visual Studio guide (PR #147710)

[David Spickett via llvm-commits]

https://github.com/DavidSpickett created https://github.com/llvm/llvm-project/pull/147710

As it very specifically wants ARM64 not what you'd guess which is arm64.

This guide talks about VS2019 that probably has little or no Windows on Arm support, but I don't have the bandwidth to follow the whole thing and update it right now.

I think this small change will be enough for most people who download the latest Visual Studio on a Windows on Arm machine.

>From ee23cebcfa940e322e2243ea33ceb080e4534346 Mon Sep 17 00:00:00 2001
From: David Spickett <david.spickett at linaro.org>
Date: Wed, 9 Jul 2025 13:03:03 +0100
Subject: [PATCH] [llvm][docs] Note Windows on Arm setting in Visual Studio
 guide

As it very specifically wants ARM64 not what you'd guess which is
arm64.

This guide talks about VS2019 that probably has little or no
Windows on Arm support, but I don't have the bandwidth to follow
the whole thing and update it right now.

I think this small change will be enough for most people who
download the latest Visual Studio on a Windows on Arm machine.
---
 llvm/docs/GettingStartedVS.rst | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/llvm/docs/GettingStartedVS.rst b/llvm/docs/GettingStartedVS.rst
index 4b15272635fbe..6ccd38bd7cc95 100644
--- a/llvm/docs/GettingStartedVS.rst
+++ b/llvm/docs/GettingStartedVS.rst
@@ -126,6 +126,15 @@ These instruction were tested with Visual Studio 2019 and Python 3.9.6:
        cmake -S llvm\llvm -B build -DLLVM_ENABLE_PROJECTS=clang -DLLVM_TARGETS_TO_BUILD=X86 -Thost=x64
        exit
 
+   .. note::
+     By default, the Visual Studio project files generated by CMake use the
+     32-bit toolset. If you are developing on a 64-bit version of Windows and
+     want to use the 64-bit toolset, pass the ``-Thost=x64`` flag when
+     generating the Visual Studio solution. This requires CMake 3.8.0 or later.
+
+     For Windows on Arm the equivalent is ``-Thost=ARM64``, but this the default
+     for those hosts, so you do not have to use this option.
+
    ``LLVM_ENABLE_PROJECTS`` specifies any additional LLVM projects you want to
    build while ``LLVM_TARGETS_TO_BUILD`` selects the compiler targets. If
    ``LLVM_TARGETS_TO_BUILD`` is omitted by default all targets are built