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Support SLANG_PLUGIN_PATH env var for custom slang plugin location #4131

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Support SLANG_PLUGIN_PATH env var for custom slang plugin location #4131

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6e3c3f1
Support SLANG_PLUGIN_PATH env var for custom slang plugin location
oharboe Apr 10, 2026
7125f81
Move SLANG_PLUGIN_PATH to variables.yaml with default "slang"
oharboe Apr 11, 2026
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2 changes: 2 additions & 0 deletions docs/user/FlowVariables.md
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Original file line number Diff line number Diff line change
Expand Up @@ -273,6 +273,7 @@ configuration file.
| <a name="SKIP_REPAIR_TIE_FANOUT"></a>SKIP_REPAIR_TIE_FANOUT| Skip repair_tie_fanout at floorplan step.| 0|
| <a name="SKIP_REPORT_METRICS"></a>SKIP_REPORT_METRICS| If set to 1, then metrics, report_metrics does nothing. Useful to speed up builds.| 0|
| <a name="SKIP_VT_SWAP"></a>SKIP_VT_SWAP| Do not perform VT swap to improve QoR (default: do VT swap).| |
| <a name="SLANG_PLUGIN_PATH"></a>SLANG_PLUGIN_PATH| Path to the slang plugin for Yosys. This can be a full path to a custom-built plugin (e.g. for Bazel builds) or just the plugin name.| slang|
| <a name="SLEW_MARGIN"></a>SLEW_MARGIN| Specifies a slew margin when fixing max slew violations. This option allows you to overfix.| |
| <a name="SWAP_ARITH_OPERATORS"></a>SWAP_ARITH_OPERATORS| Improve timing QoR by swapping ALU and MULT arithmetic operators.| |
| <a name="SYNTH_ARGS"></a>SYNTH_ARGS| Optional synthesis variables for yosys.| |
Expand Down Expand Up @@ -326,6 +327,7 @@ configuration file.
- [PRE_SYNTH_TCL](#PRE_SYNTH_TCL)
- [SDC_FILE](#SDC_FILE)
- [SDC_GUT](#SDC_GUT)
- [SLANG_PLUGIN_PATH](#SLANG_PLUGIN_PATH)
- [SYNTH_ARGS](#SYNTH_ARGS)
- [SYNTH_BLACKBOXES](#SYNTH_BLACKBOXES)
- [SYNTH_CANONICALIZE_TCL](#SYNTH_CANONICALIZE_TCL)
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2 changes: 1 addition & 1 deletion flow/scripts/synth_preamble.tcl
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Expand Up @@ -44,7 +44,7 @@ proc read_design_sources { } {
}

if { [env_var_equals SYNTH_HDL_FRONTEND slang] } {
plugin -i slang
plugin -i $::env(SLANG_PLUGIN_PATH)

set slang_args [list \
-D SYNTHESIS --keep-hierarchy --compat=vcs --ignore-assertions --top $::env(DESIGN_NAME) \
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7 changes: 7 additions & 0 deletions flow/scripts/variables.yaml
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Expand Up @@ -238,6 +238,13 @@ SYNTH_HDL_FRONTEND:
command.
stages:
- synth
SLANG_PLUGIN_PATH:
description: >
Path to the slang plugin for Yosys. This can be a full path to a
custom-built plugin (e.g. for Bazel builds) or just the plugin name.
default: slang
stages:
- synth
SYNTH_SLANG_ARGS:
description: >
Additional arguments passed to the slang frontend during synthesis.
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