[AIEX] update_ore_test_checks: don't chain asm update for remark-only tests

With --update-llc-checks, update_ore_test_checks.py stripped the remark RUN
lines and always invoked update_llc_test_checks.py. For a test whose only RUN
lines are remark runs, that handed the sibling script a file with no RUN lines,
which crashed in update_llc_test_checks.py main() with an UnboundLocalError
(output_type is only bound inside the per-RUN-line loop).

Fix it structurally at the orchestration layer: only delegate to the asm/MIR
update script when the test actually has a non-remark RUN line to regenerate
(has_asm_run_lines). A remark-only test now skips the asm step and just
regenerates its remark CHECK lines.

Add a regression test (x86-ore-chain-update-no-asm) covering a remark-only
test updated with --update-llc-checks, including UTC_ARGS idempotency.

Author: F-Stuckmann

llvm/test/tools/UpdateTestChecks/update_ore_test_checks/Inputs/x86-ore-chain-update-no-asm.ll

@@ -0,0 +1,18 @@
+; This file is licensed under the Apache License v2.0 with LLVM Exceptions.
+; See https://llvm.org/LICENSE.txt for license information.
+; SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+;
+; (c) Copyright 2026 Advanced Micro Devices, Inc. or its affiliates
+
+; RUN: llc -mtriple=x86_64-linux-gnu -pass-remarks-output=- -pass-remarks-filter=asm-printer %s -o /dev/null | FileCheck %s
+
+; Regression fixture: a remark-only test (no asm RUN line) updated with
+; --update-llc-checks. The asm-update step has nothing to regenerate and must
+; be skipped, rather than stripping the remark RUN line and handing the sibling
+; update_llc_test_checks.py a file with no RUN lines (which crashed with
+; UnboundLocalError). Only REMARKS-style CHECK lines should be produced.
+
+define i32 @add(i32 %a, i32 %b) {
+  %c = add i32 %a, %b
+  ret i32 %c
+}

llvm/test/tools/UpdateTestChecks/update_ore_test_checks/Inputs/x86-ore-chain-update-no-asm.ll.expected

@@ -0,0 +1,44 @@
+; NOTE: Assertions have been autogenerated by utils/update_ore_test_checks.py UTC_ARGS: --update-llc-checks
+; This file is licensed under the Apache License v2.0 with LLVM Exceptions.
+; See https://llvm.org/LICENSE.txt for license information.
+; SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+;
+; (c) Copyright 2026 Advanced Micro Devices, Inc. or its affiliates
+
+; RUN: llc -mtriple=x86_64-linux-gnu -pass-remarks-output=- -pass-remarks-filter=asm-printer %s -o /dev/null | FileCheck %s
+
+; Regression fixture: a remark-only test (no asm RUN line) updated with
+; --update-llc-checks. The asm-update step has nothing to regenerate and must
+; be skipped, rather than stripping the remark RUN line and handing the sibling
+; update_llc_test_checks.py a file with no RUN lines (which crashed with
+; UnboundLocalError). Only REMARKS-style CHECK lines should be produced.
+
+define i32 @add(i32 %a, i32 %b) {
+; CHECK: --- !Analysis
+; CHECK-NEXT: Pass:            asm-printer
+; CHECK-NEXT: Name:            InstructionMix
+; CHECK-NEXT: Function:        add
+; CHECK-NEXT: Args:
+; CHECK-NEXT:   - String:          'BasicBlock: '
+; CHECK-NEXT:   - BasicBlock:      ''
+; CHECK-NEXT:   - String:          "\n"
+; CHECK-NEXT:   - String:          'leal	'
+; CHECK-NEXT:   - String:          ': '
+; CHECK-NEXT:   - INST_leal:       '1'
+; CHECK-NEXT:   - String:          "\n"
+; CHECK-NEXT:   - String:          retq
+; CHECK-NEXT:   - String:          ': '
+; CHECK-NEXT:   - INST_retq:       '1'
+; CHECK-NEXT:   - String:          "\n"
+; CHECK-NEXT: ...
+; CHECK: --- !Analysis
+; CHECK-NEXT: Pass:            asm-printer
+; CHECK-NEXT: Name:            InstructionCount
+; CHECK-NEXT: Function:        add
+; CHECK-NEXT: Args:
+; CHECK-NEXT:   - NumInstructions: '2'
+; CHECK-NEXT:   - String:          ' instructions in function'
+; CHECK-NEXT: ...
+  %c = add i32 %a, %b
+  ret i32 %c
+}

llvm/test/tools/UpdateTestChecks/update_ore_test_checks/x86-ore-chain-update-no-asm.test

@@ -0,0 +1,12 @@
+# REQUIRES: x86-registered-target
+## Remark-only test (no asm RUN line) updated with --update-llc-checks. The
+## asm-update step must be skipped because there is nothing to regenerate;
+## previously it stripped the remark RUN line and crashed the sibling
+## update_llc_test_checks.py with an UnboundLocalError on an empty run list.
+
+# RUN: cp -f %S/Inputs/x86-ore-chain-update-no-asm.ll %t.ll && %update_ore_test_checks --update-llc-checks %t.ll
+# RUN: diff -u %S/Inputs/x86-ore-chain-update-no-asm.ll.expected %t.ll
+
+## Idempotency via UTC_ARGS (no --update-llc-checks on the command line):
+# RUN: %update_ore_test_checks %t.ll
+# RUN: diff -u %S/Inputs/x86-ore-chain-update-no-asm.ll.expected %t.ll

llvm/utils/update_ore_test_checks.py

@@ -210,6 +210,14 @@ def split_pipeline(run_line):
     return stages
 
 
+def has_asm_run_lines(run_lines):
+    """True if any RUN line is a non-remark run the sibling asm/MIR update
+    script can regenerate. A test whose RUN lines are all remark runs has no
+    assembly to update, so the sibling script must not be invoked on it (after
+    the remark runs are stripped it would see a file with no RUN lines)."""
+    return any(not PASS_REMARKS_OUTPUT_RE.search(rl) for rl in run_lines)
+
+
 def parse_remark_runs(run_lines, test_path):
     """Identify RUN lines that produce remark YAML output.
 
@@ -522,15 +530,19 @@ def main():
         else:
             asm_flag = parse_utc_args(first_line)
 
-        # Optionally regenerate assembly CHECK lines first.
-        if asm_flag:
+        run_lines = common.find_run_lines(test_path, input_lines)
+
+        # Regenerate assembly CHECK lines first, but only when there is a
+        # non-remark RUN line to regenerate. Delegating for a remark-only test
+        # would hand the sibling script a file with no RUN lines.
+        if asm_flag and has_asm_run_lines(run_lines):
             invoke_asm_update_script(test_path, args.llc_binary, asm_flag)
 
-            # Re-read the file after the asm script rewrote it.
+            # Re-read the file (and its RUN lines) after the asm script rewrote it.
             with open(test_path) as f:
                 input_lines = [l.rstrip() for l in f]
+            run_lines = common.find_run_lines(test_path, input_lines)
 
-        run_lines = common.find_run_lines(test_path, input_lines)
         remark_runs = parse_remark_runs(run_lines, test_path)
 
         if not remark_runs: