build: add support for building CUDA files with clang

This avoids using the CUDA SDK at all; instead, we provide a minimal
reimplementation of the basic functionality that lavfi actually uses.
It generates very similar code to what NVCC produces.

The header contains no implementation code derived from the SDK.
The function and type declarations are derived from the SDK only to the
extent required to build a compatible implementation. This is generally
accepted to qualify as fair use.

Because this option does not require the proprietary SDK, it does not require
the "--enable-nonfree" flag in configure.

Signed-off-by: Timo Rothenpieler <timo@rothenpieler.org>

1 files changed, 45 insertions, 22 deletions

diff --git a/configure b/configure
index 5a4f507..bddc05b 100755
--- a/configure
+++ b/configure
@@ -322,6 +322,7 @@ External library support:
   --disable-amf            disable AMF video encoding code [autodetect]
   --disable-audiotoolbox   disable Apple AudioToolbox code [autodetect]
   --enable-cuda-nvcc       enable Nvidia CUDA compiler [no]
+  --disable-cuda-llvm      disable CUDA compilation using clang [autodetect]
   --disable-cuvid          disable Nvidia CUVID support [autodetect]
   --disable-d3d11va        disable Microsoft Direct3D 11 video acceleration code [autodetect]
   --disable-dxva2          disable Microsoft DirectX 9 video acceleration code [autodetect]
@@ -370,7 +371,7 @@ Toolchain options:
   --cxx=CXX                use C compiler CXX [$cxx_default]
   --objcc=OCC              use ObjC compiler OCC [$cc_default]
   --dep-cc=DEPCC           use dependency generator DEPCC [$cc_default]
-  --nvcc=NVCC              use Nvidia CUDA compiler NVCC [$nvcc_default]
+  --nvcc=NVCC              use Nvidia CUDA compiler NVCC or clang [$nvcc_default]
   --ld=LD                  use linker LD [$ld_default]
   --pkg-config=PKGCONFIG   use pkg-config tool PKGCONFIG [$pkg_config_default]
   --pkg-config-flags=FLAGS pass additional flags to pkgconf []
@@ -1038,12 +1039,16 @@ test_nvcc(){
     tmpcu_=$TMPCU
     tmpo_=$TMPO
     [ -x "$(command -v cygpath)" ] && tmpcu_=$(cygpath -m $tmpcu_) && tmpo_=$(cygpath -m $tmpo_)
-    test_cmd $nvcc -ptx $NVCCFLAGS "$@" $NVCC_C $(nvcc_o $tmpo_) $tmpcu_
+    test_cmd $nvcc $nvccflags "$@" $NVCC_C $(nvcc_o $tmpo_) $tmpcu_
 }
 
 check_nvcc() {
     log check_nvcc "$@"
-    test_nvcc <<EOF
+    name=$1
+    shift 1
+    disabled $name && return
+    disable $name
+    test_nvcc "$@" <<EOF && enable $name
 extern "C" {
     __global__ void hello(unsigned char *data) {}
 }
@@ -1814,6 +1819,7 @@ HWACCEL_AUTODETECT_LIBRARY_LIST="
     audiotoolbox
     crystalhd
     cuda
+    cuda_llvm
     cuvid
     d3d11va
     dxva2
@@ -2987,8 +2993,10 @@ v4l2_m2m_deps="linux_videodev2_h sem_timedwait"
 
 hwupload_cuda_filter_deps="ffnvcodec"
 scale_npp_filter_deps="ffnvcodec libnpp"
-scale_cuda_filter_deps="ffnvcodec cuda_nvcc"
-thumbnail_cuda_filter_deps="ffnvcodec cuda_nvcc"
+scale_cuda_filter_deps="ffnvcodec"
+scale_cuda_filter_deps_any="cuda_nvcc cuda_llvm"
+thumbnail_cuda_filter_deps="ffnvcodec"
+thumbnail_cuda_filter_deps_any="cuda_nvcc cuda_llvm"
 transpose_npp_filter_deps="ffnvcodec libnpp"
 
 amf_deps_any="libdl LoadLibrary"
@@ -3547,7 +3555,8 @@ zscale_filter_deps="libzimg const_nan"
 scale_vaapi_filter_deps="vaapi"
 vpp_qsv_filter_deps="libmfx"
 vpp_qsv_filter_select="qsvvpp"
-yadif_cuda_filter_deps="ffnvcodec cuda_nvcc"
+yadif_cuda_filter_deps="ffnvcodec"
+yadif_cuda_filter_deps_any="cuda_nvcc cuda_llvm"
 
 # examples
 avio_dir_cmd_deps="avformat avutil"
@@ -3651,8 +3660,6 @@ version_script='--version-script'
 objformat="elf32"
 x86asmexe_default="nasm"
 windres_default="windres"
-nvcc_default="nvcc"
-nvccflags_default="-gencode arch=compute_30,code=sm_30 -O2"
 striptype="direct"
 
 # OS
@@ -4220,6 +4227,20 @@ windres_default="${cross_prefix}${windres_default}"
 
 sysinclude_default="${sysroot}/usr/include"
 
+if enabled cuda_sdk; then
+    warn "Option --enable-cuda-sdk is deprecated. Use --enable-cuda-nvcc instead."
+    enable cuda_nvcc
+fi
+
+if enabled cuda_nvcc; then
+    nvcc_default="nvcc"
+    nvccflags_default="-gencode arch=compute_30,code=sm_30 -O2"
+else
+    nvcc_default="clang"
+    nvccflags_default="--cuda-gpu-arch=sm_30 -O2"
+    NVCC_C=""
+fi
+
 set_default arch cc cxx doxygen pkg_config ranlib strip sysinclude \
     target_exec x86asmexe nvcc
 enabled cross_compile || host_cc_default=$cc
@@ -6060,9 +6081,21 @@ check_type "d3d9.h dxva2api.h" DXVA2_ConfigPictureDecode -D_WIN32_WINNT=0x0602
 
 check_type "vdpau/vdpau.h" "VdpPictureInfoHEVC"
 
-if enabled cuda_sdk; then
-    warn "Option --enable-cuda-sdk is deprecated. Use --enable-cuda-nvcc instead."
-    enable cuda_nvcc
+if [ -z "$nvccflags" ]; then
+    nvccflags=$nvccflags_default
+fi
+
+if enabled x86_64 || enabled ppc64 || enabled aarch64; then
+    nvccflags="$nvccflags -m64"
+else
+    nvccflags="$nvccflags -m32"
+fi
+
+if enabled cuda_nvcc; then
+    nvccflags="$nvccflags -ptx"
+else
+    nvccflags="$nvccflags -S -nocudalib -nocudainc --cuda-device-only -include${source_link}/compat/cuda/cuda_runtime.h"
+    check_nvcc cuda_llvm
 fi
 
 if ! disabled ffnvcodec; then
@@ -6140,7 +6173,7 @@ for func in $COMPLEX_FUNCS; do
 done
 
 # these are off by default, so fail if requested and not available
-enabled cuda_nvcc         && { check_nvcc || die "ERROR: failed checking for nvcc."; }
+enabled cuda_nvcc         && { check_nvcc cuda_nvcc || die "ERROR: failed checking for nvcc."; }
 enabled chromaprint       && require chromaprint chromaprint.h chromaprint_get_version -lchromaprint
 enabled decklink          && { require_headers DeckLinkAPI.h &&
                                { test_cpp_condition DeckLinkAPIVersion.h "BLACKMAGIC_DECKLINK_API_VERSION >= 0x0a090500" || die "ERROR: Decklink API version must be >= 10.9.5."; } }
@@ -6701,16 +6734,6 @@ if [ -z "$optflags" ]; then
     fi
 fi
 
-if [ -z "$nvccflags" ]; then
-    nvccflags=$nvccflags_default
-fi
-
-if enabled x86_64 || enabled ppc64 || enabled aarch64; then
-    nvccflags="$nvccflags -m64"
-else
-    nvccflags="$nvccflags -m32"
-fi
-
 check_optflags(){
     check_cflags "$@"
     enabled lto && check_ldflags "$@"