[mlir][test] Add missing LIT config for `mlir-cpu-config` + emulator

[awarzynski]

Summary

Similarly to when using lli, make sure that when using
mlir-cpu-runner with an emulator, a full path to mlir-cpu-runner is
used. Otherwise mlir-cpu-runner won't be found and you will get the
following error:

Error while loading mlir-cpu-runner: No such file or directory

This patch should fix:

• https://lab.llvm.org/buildbot/#/builders/179

The breakage was originally introduced in
https://reviews.llvm.org/D155405.

[DavidSpickett]

If it's easier, you can pass PATH to the emulated process:

-E var=value         QEMU_SET_ENV      sets targets environment variable (see below)

That's assuming you know at this point what the final PATH will be.

[c-rhodes]

mlir/test/Integration/lit.local.cfg

50

should this be mlir_tools_dir? Looks like it can be configured separately in CMake?

[DavidSpickett]

Mind you, that's QEMU specific and who knows what else is on PATH.

[awarzynski]

Replace config.llvm_tools_dir with config.mlir_tools_dir

Thanks Cullen!

[c-rhodes]

LGTM cheers

mlir/test/Integration/lit.local.cfg

if config.arm_emulator_executable:
             lli_cmd = llvm_config.use_llvm_tool(
                 "lli",
                 search_env="LLI",
                 required=True,
                 search_paths=[config.llvm_tools_dir],
                 use_installed=False,
             )
 
+        if config.arm_emulator_mlir_cpu_runner_executable:
+            mcr_cmd = config.arm_emulator_mlir_cpu_runner_executable
+        else:
+            # Top-level LIT config adds llvm_tools_dir to PATH but this is lost
+            # when running under an emulator. If the user didn't specify an
+            # mlir-cpu-runner executable, use absolute path
+            # %llvm_tools_dir/mlir-cpu-runner.
+            mcr_cmd = llvm_config.use_llvm_tool(
+                "mlir-cpu-runner",
+                search_env="MLIR_CPU_RUNNER",
+                required=True,
+                search_paths=[config.mlir_tools_dir],
+                use_installed=False,
+            )
+
         # Run test in emulator (qemu or armie)
         emulation_cmd = (
             f"{config.arm_emulator_executable} {config.arm_emulator_options}"
         )
 
-        if config.arm_emulator_mlir_cpu_runner_executable:
-          mcr_cmd = config.arm_emulator_mlir_cpu_runner_executable
-
         lli_cmd = f"{emulation_cmd} {lli_cmd}"
         mcr_cmd = f"{emulation_cmd} {mcr_cmd}"
 
     return (lli_cmd, mcr_cmd)
 
 
 aarch64_lli_cmd, aarch64_mcr_cmd = configure_aarch64_lli_and_mcr_cmd()