[llvm-exegesis] Make rvv/filter.test deterministic

This should prevent the flaky failures that have been plaguing the
buildbots since the test was introduced and allow for offline
investigation without disrupting CI.

Reviewers: topperc, mshockwave

Reviewed By: mshockwave

Pull Request: #170014

Author: boomanaiden154

llvm/test/tools/llvm-exegesis/RISCV/rvv/filter.test

@@ -1,7 +1,9 @@
+# TODO(mshockwave): We use a fixed seed for this test because sometimes it
+# will fail to generate any snippet because it is unable to assign unique
+# def and use registers.
 # RUN: llvm-exegesis -mtriple=riscv64 -mcpu=sifive-x280 -benchmark-phase=assemble-measured-code --mode=inverse_throughput --opcode-name=PseudoVNCLIPU_WX_M1_MASK \
-# RUN:    --riscv-filter-config='vtype = {VXRM: rod, AVL: VLMAX, SEW: e(8|16), Policy: ta/mu}' --max-configs-per-opcode=1000 --min-instructions=10 | FileCheck %s
-# Sometimes it'll fail to generate any snippet because it's unable to assign unique def and use registers.
-# ALLOW_RETRIES: 2
+# RUN:    --riscv-filter-config='vtype = {VXRM: rod, AVL: VLMAX, SEW: e(8|16), Policy: ta/mu}' --max-configs-per-opcode=1000 --min-instructions=10 \
+# RUN:    -random-generator-seed=5 | FileCheck %s
 
 # CHECK: config:          'vtype = {VXRM: rod, AVL: VLMAX, SEW: e8, Policy: ta/mu}'
 # CHECK: config:          'vtype = {VXRM: rod, AVL: VLMAX, SEW: e16, Policy: ta/mu}'