[pytorch] fix hipify_python (#70619)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70619

This Diff improves `hipify_python`, which is needed for AMD GPUs.

Change 1:
```
if (c == "," or ind == len(kernel_string) - 1) and closure == 0:
```
This is needed to deal with the following case (ex: https://github.com/pytorch/pytorch/blob/master/aten/src/ATen/test/cuda_vectorized_test.cu#L111)
```
kernel<<<val, func()>>>(...)
// In this case, kernel_string is "val, func()"
// so closure gets 0 when ind == len(kernel_string) - 1.
```

Change 2:
```
mask_comments()
```
This is needed to deal with a case where "<<<" is included in a comment or a string literal (ex: https://github.com/pytorch/pytorch/blob/master/torch/csrc/deploy/interpreter/builtin_registry.cpp#L71)
```
abc = "<<<XYZ>>>"
// Though this <<<XYZ>>> is irrelevant to CUDA kernels,
// the current script attempts to hipify this and fails.
```

Test Plan:
This patch fixes errors I encountered by running
```
python3 tools/amd_build/build_amd.py
```

I confirmed, with Linux `diff`, that this patch does not change HIP code that was generated successfully with the original script.

Reviewed By: hyuen

Differential Revision: D33407743

fbshipit-source-id: bec822e040a154be4cda1c294536792ca8d596ae

torch/utils/hipify/hipify_python.py

@@ -247,7 +247,7 @@ def add_dim3(kernel_string, cuda_kernel):
             closure += 1
         elif c == ")":
             closure -= 1
-        elif (c == "," or ind == len(kernel_string) - 1) and closure == 0:
+        if (c == "," or ind == len(kernel_string) - 1) and closure == 0:
             arg_locs[count]['end'] = ind + (c != ",")
             count += 1
             if count < 2:
@@ -356,8 +356,43 @@ def processKernelLaunches(string, stats):
 
         return kernel_positions
 
+    # Replace comments and string literals from the code so that find_kernel_bounds does not
+    # wrongly capture kernels in comments and string literals.
+    # This function replaces them with "x" to keep positions.
+    def mask_comments(string):
+        in_comment = ''
+        prev_c = ''
+        new_string = ''
+        for c in string:
+            if in_comment == '':
+                # Outside comments
+                if c == '/' and prev_c == '/':
+                    in_comment = '//'
+                elif c == '*' and prev_c == '/':
+                    in_comment = '/*'
+                elif c == '"' and prev_c != '\\' and prev_c != "'":
+                    in_comment = '"'
+            elif in_comment == '//':
+                # In // xxx
+                if c == '\r' or c == '\n':
+                    in_comment = ''
+            elif in_comment == '/*':
+                # In /* xxx */
+                if c == '/' and prev_c == '*':
+                    in_comment = ''
+            elif in_comment == '"':
+                # In ""
+                if c == '"' and prev_c != '\\':
+                    in_comment = ''
+            prev_c = c
+            if in_comment == '':
+                new_string += c
+            else:
+                new_string += 'x'
+        return new_string
+
     # Grab positional ranges of all kernel launches
-    get_kernel_positions = list(find_kernel_bounds(string))
+    get_kernel_positions = list(find_kernel_bounds(mask_comments(string)))
     output_string = string
 
     # Replace each CUDA kernel with a HIP kernel.