CI: Add ability to generate patch coverage reports

Makefile.in

@@ -603,9 +603,16 @@ COVERAGE_DIR := obj_coverage
 
 ifeq ($(CFG_WITH_DEV_GCOV),yes)
 
-FASTCOV := nodist/fastcov.py
+# Figure out base and head refs for coverage report
+COVERAGE_REF_BASE := $(if $(COVERAGE_BASE),$(shell git rev-parse --short $(COVERAGE_BASE)))
+COVERAGE_REF_HEAD := $(shell git rev-parse --short HEAD)
+override undefine COVERAGE_BASE # Use the above variabels instead
+COVERAGE_PATCH_FILE := $(COVERAGE_DIR)/$(if $(COVERAGE_REF_BASE),$(COVERAGE_REF_BASE).patch,.none.pach)
 
+# 'fastcov' setup
+FASTCOV := nodist/fastcov.py
 FASTCOV_OPT := -j $(shell nproc)
+FASTCOV_OPT += --lcov
 FASTCOV_OPT += --process-gcno
 FASTCOV_OPT += --branch-coverage
 FASTCOV_OPT += --dump-statistic
@@ -642,7 +649,9 @@ FASTCOV_OPT += BROKEN_BASE_RTN
 FASTCOV_OPT += SELF_CHECK
 FASTCOV_OPT += 'if (VL_UNCOVERABLE'
 FASTCOV_OPT += '} else if (VL_UNCOVERABLE'
+FASTCOV_OPT += $(if $(COVERAGE_REF_BASE),--diff-filter $(COVERAGE_PATCH_FILE))
 
+# 'genhtml' setup
 GENHTML := genhtml
 GENHTML_OPT := -j $(shell nproc)
 GENHTML_OPT += --branch-coverage
@@ -650,26 +659,43 @@ GENHTML_OPT += --demangle-cpp
 GENHTML_OPT += --rc branch_coverage=1
 GENHTML_OPT += --rc genhtml_hi_limit=100
 GENHTML_OPT += --ignore-errors negative
-GENHTML_OPT += --header-title "Verilator code coverage report"
+ifeq ($(COVERAGE_REF_BASE),)
+GENHTML_OPT += --header-title "Code coverage for Verilator $(shell git describe --dirty)"
+else
+GENHTML_OPT += --header-title "Patch coverage for Verilator $(COVERAGE_REF_BASE)..$(COVERAGE_REF_HEAD)$(if $(git status --porcelain),,-dirty)"
+endif
+GENHTML_OPT += --flat
+GENHTML_OPT += --precision 2
+GENHTML_OPT += --legend
+GENHTML_OPT += --show-proportion
+GENHTML_OPT += --filter brace,blank,range
 
 # There are loads (~20k combined), but using this seems fine on modern hardware
 GCNO_FILES = $(shell find . -name '*.gcno')
 GCDA_FILES = $(shell find . -name '*.gcda')
 
+# Patch file to filter coverage with - unused if doing full coverage
+$(COVERAGE_PATCH_FILE):
+	@mkdir -p $(COVERAGE_DIR)
+	@touch $@
+	$(if $(COVERAGE_REF_BASE), git diff $(COVERAGE_REF_BASE) > $(COVERAGE_PATCH_FILE))
+
 # Combine all .gcda coverage date files into lcov .info file
-$(COVERAGE_DIR)/verilator.info: $(GCNO_FILES) $(GCDA_FILES)
+$(COVERAGE_DIR)/verilator.info: $(COVERAGE_PATCH_FILE) $(GCNO_FILES) $(GCDA_FILES)
 	@echo "####################################################################"
 	@echo "# fastcov: combining all .gcda files into lcov .info"
 	@echo "####################################################################"
-	mkdir -p $(COVERAGE_DIR)
 	/usr/bin/time -f "That took %E" \
-    $(FASTCOV) $(FASTCOV_OPT) --lcov --output $@
+    $(FASTCOV) $(FASTCOV_OPT) --output $@
+	@# Uncommitted changes not tracked, force rebuild on next run if patch coverage
+	@$(if $(COVERAGE_REF_BASE),rm $(COVERAGE_PATCH_FILE))
 
 # Build coverage report
 $(COVERAGE_DIR)/report/index.html: $(COVERAGE_DIR)/verilator.info
 	@echo "####################################################################"
 	@echo "# genhtml: Generating coverage report"
 	@echo "####################################################################"
+	@rm -rf $(COVERAGE_DIR)/reprot
 	/usr/bin/time -f "That took %E" \
     $(GENHTML) $(GENHTML_OPT) --output-directory $(COVERAGE_DIR)/report $^
 

docs/internals.rst

@@ -1695,6 +1695,15 @@ Be aware if changing a test, if that test no longer covers some item, the
 report will still contain the old coverage. Use ``make coverage-zero`` and
 rerun all tests if this is a concern.
 
+It is also possible to generate a 'patch coverage' report, which will only
+contain information about lines modified compared to a Git ref specified by the
+``COVERAGE_BASE`` Make variable (including uncommitted changes). For example,
+to see coverage of changes compared to upstream, use:
+
+.. code:: shell
+
+   make coverage-view COVERAGE_BASE=origin/master
+
 Fuzzing
 -------
 

nodist/fastcov.py

@@ -509,6 +509,13 @@ def containsMarker(markers, strBody):
 def exclProcessSource(fastcov_sources, source, exclude_branches_sw, include_branches_sw, exclude_line_marker, fallback_encodings, gcov_prefix, gcov_prefix_strip):
     source_to_open = processPrefix(source, gcov_prefix, gcov_prefix_strip)
 
+    # Before doing any work, check if this file even needs to be processed
+    if not exclude_branches_sw and not include_branches_sw:
+        # Ignore unencodable characters
+        with open(source_to_open, errors="ignore") as f:
+            if not containsMarker(exclude_line_marker + ["LCOV_EXCL"], f.read()):
+                return False
+
     # If we've made it this far we have to check every line
 
     start_line = 0
@@ -526,10 +533,8 @@ def exclProcessSource(fastcov_sources, source, exclude_branches_sw, include_bran
                 if del_exclude_br or del_include_br:
                     del fastcov_data["branches"][i]
 
-            lineIsClosingBrace = line.strip() == "}"
-
             # Skip to next line as soon as possible
-            if not containsMarker(exclude_line_marker + ["LCOV_EXCL"], line) and not lineIsClosingBrace:
+            if not containsMarker(exclude_line_marker + ["LCOV_EXCL"], line):
                 continue
 
             # Build line to function dict so can quickly delete by line number
@@ -540,7 +545,7 @@ def exclProcessSource(fastcov_sources, source, exclude_branches_sw, include_bran
                     line_to_func[l] = set()
                 line_to_func[l].add(f)
 
-            if lineIsClosingBrace or any(marker in line for marker in exclude_line_marker):
+            if any(marker in line for marker in exclude_line_marker):
                 for key in ["lines", "branches"]:
                     if i in fastcov_data[key]:
                         del fastcov_data[key][i]