[Openmp-commits] [openmp] [Libomptarget][NFC] Remove use of VLA in the AMDGPU plugin (PR #69761)

[Joseph Huber via Openmp-commits]

https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/69761

Summary:
We should not rely on a VLA in C++ for the handling of this string. The
size is a true runtime value so we cannot rely on constexpr handling. We
simply use a small vector, whose default size is most likely large
enough to handle whatever size gets output within the stack, but is safe
in cases where it is not.


>From 9b9d5c6aa3b32b933d7dd03d57ca0f2777c7d398 Mon Sep 17 00:00:00 2001
From: Joseph Huber <jhuber6 at vols.utk.edu>
Date: Fri, 20 Oct 2023 14:42:10 -0500
Subject: [PATCH] [Libomptarget][NFC] Remove use of VLA in the AMDGPU plugin

Summary:
We should not rely on a VLA in C++ for the handling of this string. The
size is a true runtime value so we cannot rely on constexpr handling. We
simply use a small vector, whose default size is most likely large
enough to handle whatever size gets output within the stack, but is safe
in cases where it is not.
---
 .../libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp   | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp b/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
index 66a25e29d016276..626ea827cc95ab2 100644
--- a/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
+++ b/openmp/libomptarget/plugins-nextgen/amdgpu/src/rtl.cpp
@@ -1568,7 +1568,7 @@ struct AMDGPUStreamManagerTy final
   hsa_agent_t Agent;
 
   /// The maximum number of queues.
-  int MaxNumQueues;
+  uint32_t MaxNumQueues;
 
   /// The size of created queues.
   int QueueSize;
@@ -2869,15 +2869,14 @@ struct AMDGPUPluginTy final : public GenericPluginTy {
         if (Status != HSA_STATUS_SUCCESS)
           return Status;
 
-        // TODO: This is not allowed by the standard.
-        char ISAName[Length];
-        Status = hsa_isa_get_info_alt(ISA, HSA_ISA_INFO_NAME, ISAName);
+        llvm::SmallVector<char> ISAName(Length);
+        Status = hsa_isa_get_info_alt(ISA, HSA_ISA_INFO_NAME, ISAName.begin());
         if (Status != HSA_STATUS_SUCCESS)
           return Status;
 
-        llvm::StringRef TripleTarget(ISAName);
+        llvm::StringRef TripleTarget(ISAName.begin(), Length);
         if (TripleTarget.consume_front("amdgcn-amd-amdhsa"))
-          Target = TripleTarget.ltrim('-').str();
+          Target = TripleTarget.ltrim('-').rtrim('\0').str();
         return HSA_STATUS_SUCCESS;
       });
       if (Err)