Opt in first 8 designs to use 'syn'

[povik]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces a new synthesis flow option (SYNTH_USE_SYN) that utilizes the built-in OpenROAD 'syn' tool via a new synth_syn.tcl script, updating the Makefile, metrics extraction, and various design configurations to support it. The code review feedback highlights several critical improvements for robustness: adding missing Verilog and SDC dependencies to the Makefile target to prevent breaking incremental builds, guarding environment variables (DONT_USE_CELLS and SYNTH_SLANG_ARGS) against Tcl runtime errors when undefined, and keeping vIdirsArgs as a proper Tcl list to safely handle paths with special characters.

[gemini-code-assist]

In the new syn synthesis flow (SYNTH_USE_SYN=1), the 1_synth target does not list $(VERILOG_FILES) or $(SDC_FILE) as dependencies. This breaks incremental builds, as modifying any Verilog source files or timing constraints will not trigger a re-synthesis of the design. Please add them to the dependency list.

ifeq ($(SYNTH_USE_SYN),1)
$(eval $(call do-step,1_synth,$(VERILOG_FILES) $(SDC_FILE) $(TECH_LEF) $(SC_LEF) $(ADDITIONAL_LEFS) $(LIB_FILES),synth_syn))
else
$(eval $(call do-step,1_synth,$(RESULTS_DIR)/1_2_yosys.v $(RESULTS_DIR)/1_2_yosys.sdc $(TECH_LEF) $(SC_LEF) $(ADDITIONAL_LEFS) $(LIB_FILES),synth_odb))
endif

[gemini-code-assist]

The environment variable DONT_USE_CELLS is not marked as required and does not have a default value in variables.json. If it is not defined in the environment, accessing $::env(DONT_USE_CELLS) directly will throw a Tcl runtime error and crash the synthesis flow. Please guard this call using env_var_exists_and_non_empty.

if { [env_var_exists_and_non_empty DONT_USE_CELLS] } {
  set_dont_use $::env(DONT_USE_CELLS)
}

[gemini-code-assist]

Instead of joining the vIdirsArgs list into a space-separated string and then using expansion ({*}) to split it back, it is cleaner and safer to keep vIdirsArgs as a proper Tcl list. This avoids potential issues with paths containing special characters or spaces.

set vIdirsArgs [list]
if { [env_var_exists_and_non_empty VERILOG_INCLUDE_DIRS] } {
  foreach dir $::env(VERILOG_INCLUDE_DIRS) {
    lappend vIdirsArgs "-I$dir"
  }
}

[gemini-code-assist]

Directly accessing $::env(SYNTH_SLANG_ARGS) can cause a runtime error if the variable is not exported to the environment. It is safer and more consistent with other environment variables to use the env_var_or_empty helper.

lappend elaborate_args {*}[env_var_or_empty SYNTH_SLANG_ARGS]