[clang] [Clang] Always pass detected CUDA path to 'clang-nvlink-wrapper' (PR #152789)

[Joseph Huber via cfe-commits]

https://github.com/jhuber6 updated https://github.com/llvm/llvm-project/pull/152789

>From b36335f136ea0ce1a29f9962d8a9b5575162a450 Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Fri, 8 Aug 2025 15:26:31 -0500
Subject: [PATCH] [Clang] Always pass detected CUDA path to
 'clang-nvlink-wrapper'

Summary:
We always want to use the detected path. The clang driver's detection is
far more sophisticated so we should use that whenever possible. Also
update the usage so we properly fall back to path instead of incorrectly
using the `/bin` if not provided.
---
 clang/lib/Driver/ToolChains/Cuda.cpp          |  9 +++++---
 clang/test/Driver/cuda-cross-compiling.c      |  8 +++++++
 .../ClangNVLinkWrapper.cpp                    | 21 ++++++++++++-------
 3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/Cuda.cpp b/clang/lib/Driver/ToolChains/Cuda.cpp
index fdfcea852b4f2..327cb5183f837 100644
--- a/clang/lib/Driver/ToolChains/Cuda.cpp
+++ b/clang/lib/Driver/ToolChains/Cuda.cpp
@@ -611,9 +611,12 @@ void NVPTX::Linker::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back(Args.MakeArgString(
         "--pxtas-path=" + Args.getLastArgValue(options::OPT_ptxas_path_EQ)));
 
-  if (Args.hasArg(options::OPT_cuda_path_EQ))
-    CmdArgs.push_back(Args.MakeArgString(
-        "--cuda-path=" + Args.getLastArgValue(options::OPT_cuda_path_EQ)));
+  if (Args.hasArg(options::OPT_cuda_path_EQ) || TC.CudaInstallation.isValid()) {
+    StringRef CudaPath = Args.getLastArgValue(
+        options::OPT_cuda_path_EQ,
+        llvm::sys::path::parent_path(TC.CudaInstallation.getBinPath()));
+    CmdArgs.push_back(Args.MakeArgString("--cuda-path=" + CudaPath));
+  }
 
   // Add paths specified in LIBRARY_PATH environment variable as -L options.
   addDirectoryList(Args, CmdArgs, "-L", "LIBRARY_PATH");
diff --git a/clang/test/Driver/cuda-cross-compiling.c b/clang/test/Driver/cuda-cross-compiling.c
index 1df231ecb4479..6717ae82d0e70 100644
--- a/clang/test/Driver/cuda-cross-compiling.c
+++ b/clang/test/Driver/cuda-cross-compiling.c
@@ -104,3 +104,11 @@
 // RUN:   -nogpulib -nogpuinc -### %s 2>&1 | FileCheck -check-prefix=STARTUP %s
 
 // STARTUP: clang-nvlink-wrapper{{.*}}"-lc" "-lm" "{{.*}}crt1.o"
+
+//
+// Test cuda path handling
+//
+// RUN: %clang -target nvptx64-nvidia-cuda -march=sm_52 --cuda-path=%S/Inputs/CUDA/usr/local/cuda \
+// RUN:   -nogpulib -nogpuinc -### %s 2>&1 | FileCheck -check-prefix=PATH %s
+
+// PATH: clang-nvlink-wrapper{{.*}}"--cuda-path={{.*}}/Inputs/CUDA/usr/local/cuda"
diff --git a/clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp b/clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp
index 4b63971214f81..47dfbf5e2e89e 100644
--- a/clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp
+++ b/clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp
@@ -286,12 +286,17 @@ struct Symbol {
 };
 
 Expected<StringRef> runPTXAs(StringRef File, const ArgList &Args) {
-  std::string CudaPath = Args.getLastArgValue(OPT_cuda_path_EQ).str();
-  std::string GivenPath = Args.getLastArgValue(OPT_ptxas_path_EQ).str();
-  Expected<std::string> PTXAsPath =
-      findProgram(Args, "ptxas", {CudaPath + "/bin", GivenPath});
+  SmallVector<StringRef, 1> SearchPaths;
+  if (Arg *A = Args.getLastArg(OPT_cuda_path_EQ))
+    SearchPaths.push_back(
+        Args.MakeArgString(StringRef(A->getValue()) + "/bin"));
+  if (Arg *A = Args.getLastArg(OPT_ptxas_path_EQ))
+    SearchPaths.push_back(Args.MakeArgString(A->getValue()));
+
+  Expected<std::string> PTXAsPath = findProgram(Args, "ptxas", SearchPaths);
   if (!PTXAsPath)
     return PTXAsPath.takeError();
+
   if (!Args.hasArg(OPT_arch))
     return createStringError(
         "must pass in an explicit nvptx64 gpu architecture to 'ptxas'");
@@ -691,9 +696,11 @@ Error runNVLink(ArrayRef<StringRef> Files, const ArgList &Args) {
   if (Args.hasArg(OPT_lto_emit_asm) || Args.hasArg(OPT_lto_emit_llvm))
     return Error::success();
 
-  std::string CudaPath = Args.getLastArgValue(OPT_cuda_path_EQ).str();
-  Expected<std::string> NVLinkPath =
-      findProgram(Args, "nvlink", {CudaPath + "/bin"});
+  SmallVector<StringRef, 1> SearchPaths;
+  if (Arg *A = Args.getLastArg(OPT_cuda_path_EQ))
+    SearchPaths.push_back(Args.MakeArgString(A->getValue() + Twine("/bin")));
+
+  Expected<std::string> NVLinkPath = findProgram(Args, "nvlink", SearchPaths);
   if (!NVLinkPath)
     return NVLinkPath.takeError();