extract calculate_time_spent from print_time_report (#127362)

Summary:
Fixes #ISSUE_NUMBER

wrap certain steps in a separate function for easier TTFB instrumentation (fb internal use case)

X-link: pytorch/pytorch#127362
Approved by: https://github.com/yanboliang, https://github.com/mengluy0125

Reviewed By: yanboliang, PaliC, mengluy0125

Differential Revision: D57889404

Pulled By: dshi7

fbshipit-source-id: d87091f0f1470c6235f532050f7d61edd0d43878

userbenchmark/dynamo/dynamobench/_dynamo/utils.py

@@ -154,12 +154,9 @@ def increment_op_count(cnt):
     op_count += cnt
 
 
-# Print a report of time spent so far
-# Ex:
-# TIMING:
-# entire_frame_compile:8.574629999999999
-# backend_compile:5.26806
-def print_time_report():
+# Calculate total time spent so far for each phase
+# For example, {'entire_frame_compile':8.574629999999999, 'backend_compile':5.26806}
+def calculate_time_spent():
     total = 0.0
     total_by_key = {}
     for timings in frame_phase_timing.values():
@@ -170,6 +167,17 @@ def print_time_report():
             else:
                 total_by_key[key] += timing
 
+    return total_by_key
+
+
+# Print a report of time spent so far
+# Ex:
+# TIMING:
+# entire_frame_compile:8.574629999999999
+# backend_compile:5.26806
+def print_time_report():
+    total_by_key = calculate_time_spent()
+
     out = "TIMING:"
     for key, value in total_by_key.items():
         out = f"{out} {key}:{round(value, 5)}"