[libomptarget][nvptx] Drop printf to enable ffreestanding

[JonChesterfield]

Summary

The nvptx devicertl compiles on more platforms if separated from
glibc. This patch disables printf from the devicertl as the lowering in
clang does not trigger with ffreestanding enabled.

Without ffreestanding, stdint et al include the ones from glibc.

This does not solve the general problem of compiling openmp on systems where
glibc causes compilation failure. It does allow running tests that don't use
libc headers.

[JonChesterfield]

The problems with stdio etc remain for tests that use it, symptoms are like

In file included from /usr/include/stdio.h:39:
/usr/include/x86_64-linux-gnu/bits/types/__fpos_t.h:12:3: error: unknown type name '__off_t'
  __off_t __pos;

usr/include/stdio.h:603:8: error: unknown type name '__ssize_t'; did you mean 'ssize_t'?
extern __ssize_t __getdelim (char **__restrict __lineptr,

[JonChesterfield]

Remembered nvptx64 is 32 bit, installed gcc-multilibs, can now build trunk without this patch. Closing.

openmp/libomptarget/deviceRTLs/nvptx/CMakeLists.txt

set(cuda_src_files
   ${devicertl_common_directory}/src/sync.cu
   ${devicertl_common_directory}/src/task.cu
   ${devicertl_common_directory}/src/shuffle.cpp
   src/target_impl.cu
 )
 
 # Set flags for LLVM Bitcode compilation.
 set(bc_flags -S -x c++ -O1 -std=c++14
+             -ffreestanding
              -mllvm -openmp-opt-disable
              -target nvptx64
              -Xclang -emit-llvm-bc
              -Xclang -aux-triple -Xclang ${aux_triple}
              -fopenmp -fopenmp-cuda-mode -Xclang -fopenmp-is-device
              -Xclang -target-feature -Xclang +ptx61
              -D__CUDACC__
              -I${devicertl_base_directory}

openmp/libomptarget/deviceRTLs/nvptx/src/target_impl.h

 //===------------ target_impl.h - NVPTX OpenMP GPU options ------- CUDA -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // Definitions of target specific functions
 //
 //===----------------------------------------------------------------------===//
 #ifndef _TARGET_IMPL_H_
 #define _TARGET_IMPL_H_
 
-#include <inttypes.h>
-#include <stdio.h>
-#include <stdlib.h>
-
 #include "nvptx_interface.h"
 
+#include <stddef.h>
+#include <stdint.h>
+
+// subset of inttypes.h
+#define PRId64 "ld"
+#define PRIu64 "lu"
+
 #define INLINE inline __attribute__((always_inline))
 #define NOINLINE __attribute__((noinline))
 #define ALIGN(N) __attribute__((aligned(N)))
 
 ////////////////////////////////////////////////////////////////////////////////
 // Kernel options
 ////////////////////////////////////////////////////////////////////////////////
 
enum DATA_SHARING_SIZES {
   // The size of the preallocated shared memory buffer per team
   DS_Shared_Memory_Size = 128,
 };
 
 enum : __kmpc_impl_lanemask_t {
   __kmpc_impl_all_lanes = ~(__kmpc_impl_lanemask_t)0
 };
 
+// Disable the printf calls as ffreestanding blocks the lowering in clang
+#define printf(...)
+
 #endif

openmp/libomptarget/deviceRTLs/nvptx/src/target_impl.cu

 EXTERN void __kmpc_impl_unset_lock(omp_lock_t *lock) {
   (void)__kmpc_atomic_exchange(lock, UNSET);
 }
 
 EXTERN int __kmpc_impl_test_lock(omp_lock_t *lock) {
   return __kmpc_atomic_add(lock, 0u);
 }
 
+void *malloc(size_t size);
+void free(void *ptr);
+
 EXTERN void *__kmpc_impl_malloc(size_t x) { return malloc(x); }
 EXTERN void __kmpc_impl_free(void *x) { free(x); }
 
 #pragma omp end declare target