[clang] [CUDA][Windows] detect installation via CUDA_PATH environment variable (PR #135299)

[via cfe-commits]

https://github.com/SquallATF created https://github.com/llvm/llvm-project/pull/135299

On Windows platforms, this patch enables detection of the CUDA installation directory by checking the CUDA_PATH environment variable.

>From 8d67d96b7ae97bd2866753d7d5dbdff26e4c4200 Mon Sep 17 00:00:00 2001
From: Peiyuan Song <squallatf at gmail.com>
Date: Fri, 11 Apr 2025 09:45:27 +0800
Subject: [PATCH] [CUDA][Windows] detect installation via CUDA_PATH environment
 variable

On Windows platforms, this patch enables detection of the CUDA installation
directory by checking the CUDA_PATH environment variable.
---
 clang/lib/Driver/ToolChains/Cuda.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/clang/lib/Driver/ToolChains/Cuda.cpp b/clang/lib/Driver/ToolChains/Cuda.cpp
index 06b0b0913d24e..f79968bbb5b65 100644
--- a/clang/lib/Driver/ToolChains/Cuda.cpp
+++ b/clang/lib/Driver/ToolChains/Cuda.cpp
@@ -158,6 +158,11 @@ CudaInstallationDetector::CudaInstallationDetector(
     Candidates.emplace_back(
         Args.getLastArgValue(clang::driver::options::OPT_cuda_path_EQ).str());
   } else if (HostTriple.isOSWindows()) {
+    if (std::optional<std::string> CudaPath =
+            llvm::sys::Process::GetEnv("CUDA_PATH")) {
+      if (!CudaPath->empty())
+        Candidates.emplace_back(std::move(*CudaPath));
+    }
     for (const char *Ver : Versions)
       Candidates.emplace_back(
           D.SysRoot + "/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v" +