[Libomptarget][CUDA] Check CUDA compatibilty correctly

[jhuber6]

Summary

We recently added support for multi-architecture binaries in
libomptarget. This is done by extracting the architecture from the
embedded image and comparing it with the major and minor version
supported by the current CUDA installation. Previously we just compared
these directly, which was not correct for binary compatibility. The CUDA
documentation states that we can consider any image with an equivalent
major or a greater or equal to minor compatible with the current image.
Change the check to use this new logic in the CUDA plugin.

Fixes #57049

[jdoerfert]

LG

[ye-luo]

a.out: /home/yeluo/opt/llvm-clang/llvm-project/llvm/include/llvm/ADT/StringRef.h:223: char llvm::StringRef::operator[](size_t) const: Assertion `Index < Length && "Invalid index!"' failed.
Aborted (core dumped)

[jhuber6]

In D131567#3712551, @ye-luo wrote:

a.out: /home/yeluo/opt/llvm-clang/llvm-project/llvm/include/llvm/ADT/StringRef.h:223: char llvm::StringRef::operator[](size_t) const: Assertion `Index < Length && "Invalid index!"' failed.
Aborted (core dumped)

Interesting, probably just messed up the string handling.

[jhuber6]

Fix index error, sizeof("x") is actually +1 because I forgot about the null byte.

[ye-luo]

Pass my tests now.

openmp/libomptarget/plugins/cuda/src/rtl.cpp

 //===----RTLs/cuda/src/rtl.cpp - Target RTLs Implementation ------- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // RTL for CUDA machine
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/StringRef.h"
+
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <cuda.h>
 #include <list>
 #include <memory>
 #include <mutex>
 #include <string>
 #include <unordered_map>
 #include <vector>
 
 #include "Debug.h"
 #include "DeviceEnvironment.h"
 #include "omptarget.h"
 #include "omptargetplugin.h"
 
 #define TARGET_NAME CUDA
 #define DEBUG_PREFIX "Target " GETNAME(TARGET_NAME) " RTL"
 
 #include "MemoryManager.h"
 
 #include "llvm/Frontend/OpenMP/OMPConstants.h"
 
+using namespace llvm;
+
 // Utility for retrieving and printing CUDA error string.
 #ifdef OMPTARGET_DEBUG
 #define CUDA_ERR_STRING(err)                                                   \
   do {                                                                         \
     if (getDebugLevel() > 0) {                                                 \
       const char *errStr = nullptr;                                            \
       CUresult errStr_status = cuGetErrorString(err, &errStr);                 \
       if (errStr_status == CUDA_ERROR_INVALID_VALUE)                           \

 }
 
 int32_t __tgt_rtl_is_valid_binary_info(__tgt_device_image *image,
                                        __tgt_image_info *info) {
   if (!__tgt_rtl_is_valid_binary(image))
     return false;
 
   // A subarchitecture was not specified. Assume it is compatible.
-  if (!info->Arch)
+  if (!info || !info->Arch)
     return true;
 
   int32_t NumberOfDevices = 0;
   if (cuDeviceGetCount(&NumberOfDevices) != CUDA_SUCCESS)
     return false;
 
+  StringRef ArchStr = StringRef(info->Arch).drop_front(sizeof("sm_"));
   for (int32_t DeviceId = 0; DeviceId < NumberOfDevices; ++DeviceId) {
     CUdevice Device;
     if (cuDeviceGet(&Device, DeviceId) != CUDA_SUCCESS)
       return false;
 
     int32_t Major, Minor;
     if (cuDeviceGetAttribute(&Major,
                              CU_DEVICE_ATTRIBUTE_COMPUTE_CAPABILITY_MAJOR,
                              Device) != CUDA_SUCCESS)
       return false;
     if (cuDeviceGetAttribute(&Minor,
                              CU_DEVICE_ATTRIBUTE_COMPUTE_CAPABILITY_MINOR,
                              Device) != CUDA_SUCCESS)
       return false;
 
-    std::string ArchStr = "sm_" + std::to_string(Major) + std::to_string(Minor);
-    if (ArchStr != info->Arch)
+    // A cubin generated for a certain compute capability is supported to run on
+    // any GPU with the same major revision and same or higher minor revision of
+    // compute capability.
+    int32_t ImageMajor = ArchStr[0] - '0';
+    int32_t ImageMinor = ArchStr[1] - '0';
+    if (Major != ImageMajor || Minor < ImageMinor)
       return false;
   }
 
   DP("Image has compatible compute capability: %s\n", info->Arch);
   return true;
 }
 
 int32_t __tgt_rtl_number_of_devices() { return DeviceRTL.getNumOfDevices(); }