[nvcc] enable multiple arch in one fatbin (#4377)

python/tvm/autotvm/measure/measure_methods.py

@@ -582,7 +582,13 @@ def check_remote(target, device_key, host=None, port=None, priority=100, timeout
 @register_func
 def tvm_callback_cuda_compile(code):
     """use nvcc to generate ptx code for better optimization"""
-    ptx = nvcc.compile_cuda(code, target="ptx", arch=AutotvmGlobalScope.current.cuda_target_arch)
+    curr_cuda_target_arch = AutotvmGlobalScope.current.cuda_target_arch
+    # e.g., target arch could be [
+    #   "-gencode", "arch=compute_52,code=sm_52",
+    #   "-gencode", "arch=compute_70,code=sm_70"
+    # ]
+    target = "fatbin" if isinstance(curr_cuda_target_arch, list) else "ptx"
+    ptx = nvcc.compile_cuda(code, target=target, arch=AutotvmGlobalScope.current.cuda_target_arch)
     return ptx
 
 
@@ -591,8 +597,10 @@ def set_cuda_target_arch(arch):
 
     Parameters
     ----------
-    arch: str
+    arch: str or list
         The argument of nvcc -arch. (e.g. "sm_51", "sm_62")
+        it can also be a count of gencode arguments pass to nvcc command line,
+        e.g., ["-gencode", "arch=compute_52,code=sm_52", "-gencode", "arch=compute_70,code=sm_70"]
     """
     AutotvmGlobalScope.current.cuda_target_arch = arch
 

python/tvm/contrib/nvcc.py

@@ -74,7 +74,10 @@ def compile_cuda(code,
     file_target = path_target if path_target else temp_target
     cmd = ["nvcc"]
     cmd += ["--%s" % target, "-O3"]
-    cmd += ["-arch", arch]
+    if isinstance(arch, list):
+        cmd += arch
+    else:
+        cmd += ["-arch", arch]
 
     if options:
         if isinstance(options, str):