synthesis: improve error messages

YOSYS_FLAGS=-v 3 will silence error messages, such as the below.

However, without this option, synthesis will give an enormous amount
of output.

Fortunately, the most common error messages, like unknown top module,
is shown during canonicalization and not specifying -v 3 doesn't
increase the logging noise noticably during the canonicalization stage.

To test:

1. modify gcd.v to rename "gcd" module to "gcdxxx"
2. Run "make synth"

Now it fails with a helpful error message

[deleted]
4. Executing HIERARCHY pass (managing design hierarchy).
ERROR: Module `gcd' not found!
ERROR: TCL interpreter returned an error: Yosys command produced an error
Command exited with non-zero status 1

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

flow/Makefile

@@ -540,7 +540,8 @@ do-yosys:
 .PHONY: do-yosys-canonicalize
 do-yosys-canonicalize: yosys-dependencies
 	mkdir -p $(RESULTS_DIR) $(LOG_DIR) $(REPORTS_DIR) $(OBJECTS_DIR)
-	($(TIME_CMD) $(YOSYS_EXE) $(YOSYS_FLAGS) -c $(SCRIPTS_DIR)/synth_canonicalize.tcl) 2>&1 | tee $(abspath $(LOG_DIR)/1_1_yosys_canonicalize.log)
+	# NOTE! YOSYS_FLAGS is omitted here because "-v 3" silences helpful error messages
+	($(TIME_CMD) $(YOSYS_EXE) -c $(SCRIPTS_DIR)/synth_canonicalize.tcl) 2>&1 | tee $(abspath $(LOG_DIR)/1_1_yosys_canonicalize.log)
 
 $(RESULTS_DIR)/1_synth.rtlil: $(YOSYS_DEPENDENCIES)
 	$(UNSET_AND_MAKE) do-yosys-canonicalize