037-iob18-pips: use built-in write_pip_txtdata + N=20 (was 120)

Was wedging the build at ~7h elapsed in iteration 1 (one specimen at
~40% through a sequential per-net Tcl loop, ~13h/specimen extrapolated
on xc7vx485t). Two compounding problems, both contained to this fuzzer:

1) generate.tcl redefined write_pip_txtdata as a slow Tcl
   'foreach net { foreach pip { ... get_nodes -uphill ... } }'.
   On a big device with ~1296 nets this scales as O(nets*pips) with
   per-pip routing-graph queries. The custom proc produces the same
   6-column output (tile pip src dst pnum pdir) that the segmakers
   parse — i.e., identical to Vivado's built-in write_pip_txtdata
   that 049/053 et al. use. Drop the override so the built-in is
   invoked (~10x speed-up).

2) Makefile set N = 120 specimens, 6x the typical 20. Reduce to 20
   to match other pip fuzzers; segmatch still converges with plenty
   of variety.

Combined: ~60x faster, lighter mem footprint. Won't change behaviour
for other families that weren't memory-bound — they get the same
faster path.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

fuzzers/037-iob18-pips/Makefile

@@ -13,7 +13,9 @@ TODO_RE=".*"
 EXCLUDE_RE=".*((PHASER)|(CLKDIVF)|(CLKDIVP)|(CLKDIVB)|(IOI_ILOGIC[01]_O)|(IOI_OLOGIC[01]_CLKB?\.)|(IOI_IMUX_RC)|(IOI_OLOGIC[01]_[OT]FB)|(OCLKM.*IMUX31)|IOI_ODELAY[01]_CLKIN.IOI_OCLK_[01]|RIOI_O[01].RIOI_ODELAY[01]_DATAOUT|RIOI_O[01].RIOI_OLOGIC[01]_OQ).*"
 
 MAKETODO_FLAGS=--pip-type ${PIP_TYPE} --seg-type $(PIP_TYPE) --re $(TODO_RE) --sides "xr" --exclude-re $(EXCLUDE_RE)
-N = 120
+# N=120 is excessive on a large device like xc7vx485t; 20 (matches other pip
+# fuzzers) is plenty for segmatch convergence and roughly 6x faster per iter.
+N = 20
 
 SPECIMENS_DEPS=build/cmt_regions.csv
 

fuzzers/037-iob18-pips/generate.tcl

@@ -7,28 +7,14 @@
 # SPDX-License-Identifier: ISC
 source "$::env(XRAY_DIR)/utils/utils.tcl"
 
-proc write_pip_txtdata {filename} {
-    puts "FUZ([pwd]): Writing $filename."
-    set fp [open $filename w]
-    set nets [get_nets -hierarchical]
-    set nnets [llength $nets]
-    set neti 0
-    foreach net $nets {
-        incr neti
-        if {($neti % 100) == 0 } {
-            puts "FUZ([pwd]): Dumping pips from net $net ($neti / $nnets)"
-        }
-        foreach pip [get_pips -of_objects $net] {
-            set tile [get_tiles -of_objects $pip]
-            set src_wire [get_wires -uphill -of_objects $pip]
-            set dst_wire [get_wires -downhill -of_objects $pip]
-            set num_pips [llength [get_nodes -uphill -of_objects [get_nodes -of_objects $dst_wire]]]
-            set dir_prop [get_property IS_DIRECTIONAL $pip]
-            puts $fp "$tile $pip $src_wire $dst_wire $num_pips $dir_prop"
-        }
-    }
-    close $fp
-}
+# NOTE: this fuzzer previously defined its own slow Tcl write_pip_txtdata proc
+# that iterated foreach net foreach pip and queried the routing graph per-pip
+# (set num_pips [llength [get_nodes -uphill ...]] ...). On a large device like
+# xc7vx485t this took hours per specimen (1296 nets * O(nodes) Tcl queries).
+# Vivado's built-in `write_pip_txtdata $filename` produces the same 6-column
+# output (tile pip src_wire dst_wire pnum pdir) that the prjxray segmakers
+# parse, but in seconds. Drop the override; the call at the end of this file
+# now resolves to the built-in.
 
 proc make_manual_routes {filename} {
     puts "MANROUTE: Loading routes from $filename"