Ukernels: enable limited debug information that is useful in profilers like Tracy. (#15756)

This is one of the steps to making Tracy sampling useful with ukernels.
It allows tracy to render correct sampling stacks and source view. It
does not by itself fix the disasm view but it's a step towards that too.

build_tools/bazel/iree_bitcode_library.bzl

diff --git a/build_tools/bazel/iree_bitcode_library.bzl b/build_tools/bazel/iree_bitcode_library.bzl
index 27b1ed6..23a00bf 100644
--- a/build_tools/bazel/iree_bitcode_library.bzl
+++ b/build_tools/bazel/iree_bitcode_library.bzl
@@ -85,6 +85,9 @@
         "-fno-ident",
         "-fdiscard-value-names",
 
+        # Limited debug information that is useful in profilers like Tracy.
+        "-gline-tables-only",
+
         # Set the size of wchar_t to 4 bytes (instead of 2 bytes).
         # This must match what the runtime is built with.
         "-fno-short-wchar",

build_tools/cmake/iree_benchmark_suite.cmake

diff --git a/build_tools/cmake/iree_benchmark_suite.cmake b/build_tools/cmake/iree_benchmark_suite.cmake
index b15afb6..4130f71 100644
--- a/build_tools/cmake/iree_benchmark_suite.cmake
+++ b/build_tools/cmake/iree_benchmark_suite.cmake
@@ -38,18 +38,44 @@
 
   if(NOT TARGET "${_RULE_TARGET_NAME}")
     cmake_path(GET _RULE_SOURCE FILENAME _MODEL_BASENAME)
+
+    # See PR #15756: PoseNet mysterious errors go away when run through iree-opt.
+    if(_RULE_SOURCE MATCHES PoseNet)
+      set(_PREOPT ON)
+    else()
+      set(_PREOPT OFF)
+    endif()
+
+    if(_PREOPT)
+      set(_PREOPT_SOURCE "${_RULE_OUTPUT_MLIR_FILE}.before-preopt")
+      set(_IMPORT_DESTINATION "${_PREOPT_SOURCE}")
+    else()
+      set(_IMPORT_DESTINATION "${_RULE_OUTPUT_MLIR_FILE}")
+    endif()
+
     add_custom_command(
-      OUTPUT "${_RULE_OUTPUT_MLIR_FILE}"
+      OUTPUT "${_IMPORT_DESTINATION}"
       COMMAND
         "${IREE_IMPORT_TFLITE_PATH}"
         "${_RULE_SOURCE}"
-        "-o=${_RULE_OUTPUT_MLIR_FILE}"
+        "-o=${_IMPORT_DESTINATION}"
         ${_RULE_IMPORT_FLAGS}
       DEPENDS
         "${_RULE_SOURCE}"
       COMMENT "Importing TFLite model ${_MODEL_BASENAME}"
       VERBATIM
     )
+
+    if(_PREOPT)
+      add_custom_command(
+        OUTPUT "${_RULE_OUTPUT_MLIR_FILE}"
+        COMMAND "iree-opt" "${_PREOPT_SOURCE}" "-o" "${_RULE_OUTPUT_MLIR_FILE}"
+        DEPENDS "${_IMPORT_DESTINATION}"
+        COMMENT "Processing TFLite model ${_MODEL_BASENAME} with iree-opt"
+        VERBATIM
+      )
+    endif()
+
     add_custom_target("${_RULE_TARGET_NAME}"
       DEPENDS
         "${_RULE_OUTPUT_MLIR_FILE}"

build_tools/cmake/iree_bitcode_library.cmake

diff --git a/build_tools/cmake/iree_bitcode_library.cmake b/build_tools/cmake/iree_bitcode_library.cmake
index 0c68562..3b21f00 100644
--- a/build_tools/cmake/iree_bitcode_library.cmake
+++ b/build_tools/cmake/iree_bitcode_library.cmake
@@ -55,6 +55,9 @@
     "-fno-ident"
     "-fdiscard-value-names"
 
+    # Limited debug information that is useful in profilers like Tracy.
+    "-gline-tables-only"
+
     # Set the size of wchar_t to 4 bytes (instead of 2 bytes).
     # This must match what the runtime is built with.
     "-fno-short-wchar"