[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 fff2a4bd4fa424fedaed4fff04a9b46f03f8ff9e Mon Sep 17 00:00:00 2001
From: Joseph Huber <hube...@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          | 10 ++++++---
 clang/test/Driver/cuda-cross-compiling.c      |  8 +++++++
 .../ClangNVLinkWrapper.cpp                    | 22 +++++++++++++------
 3 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/Cuda.cpp 
b/clang/lib/Driver/ToolChains/Cuda.cpp
index fdfcea852b4f2..847d7235441c9 100644
--- a/clang/lib/Driver/ToolChains/Cuda.cpp
+++ b/clang/lib/Driver/ToolChains/Cuda.cpp
@@ -611,9 +611,13 @@ 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_ptxas_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..c78e37a1ffe89 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 +696,12 @@ 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(StringRef(A->getValue()) + "/bin"));
+
+  Expected<std::string> NVLinkPath = findProgram(Args, "nvlink", SearchPaths);
   if (!NVLinkPath)
     return NVLinkPath.takeError();
 

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