synth: less iffy VERILOG_TOP_PARAMS code

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

Author: oharboe

flow/scripts/synth_canonicalize.tcl

@@ -1,10 +1,8 @@
 source $::env(SCRIPTS_DIR)/synth_preamble.tcl
 
-# Apply toplevel parameters (if exist)
-if {[env_var_exists_and_non_empty VERILOG_TOP_PARAMS]} {
-  dict for {key value} $::env(VERILOG_TOP_PARAMS) {
-    chparam -set $key $value $::env(DESIGN_NAME)
-  }
+dict for {key value} $::env(VERILOG_TOP_PARAMS) {
+  # Apply toplevel parameters
+  chparam -set $key $value $::env(DESIGN_NAME)
 }
 
 hierarchy -check -top $::env(DESIGN_NAME)

flow/scripts/variables.yaml

@@ -658,6 +658,7 @@ VERILOG_TOP_PARAMS:
     Apply toplevel params (if exist).
   stages:
     - synth
+  default: ""
 CORE_ASPECT_RATIO:
   description: >
     The core aspect ratio (height / width). This value is ignored if