Add a tracing framework (really just logging).

This isn't a performance tracing framework (unlike the old ruy tracing).
This is about understanding what happens inside a ruy::Mul with a view
toward documenting how ruy works.

Added a 'parametrized_example' to help play with this tracing on any
flavor of ruy::Mul call. This also serves as a more elaborate example
of how to call ruy::Mul, and as a single binary instantiating several
different instantiations of the ruy::Mul template, which is useful
for measuring binary size and showing a breakdown of ruy symbols in
a document.

A few code changes beyond tracing slipped in:
 - Improved logic in determining the traversal order in MakeBlockMap:
   In rectangular cases, since we first do the top-level rectangularness
   subdivision with linear traversal anyway, the traversal order only
   applies within each subdivision past that, so it should be based
   on sizes already divided by rectangularness. In practice this nudges
   1000x400x2000 from kFractalHilbert to kFractalU on Pixel4, without
   making an observable perf difference in that case.
 - Removed the old RUY_BLOCK_MAP_DEBUG logging code: superseded.
   Kept only a minimal hook to force a block_size_log2 choice.
 - Wrote new comments on BlockMap internals.
 - Fixed Ctx::set_runtime_enabled_paths to behave as documented:
   passing Path::kNone reverts to the default behavior (auto detect).
 - Exposed Context::set_runtime_enabled_paths.
 - Renamed UseSimpleLoop -> GetUseSimpleLoop (easier to read trace).

PiperOrigin-RevId: 352695092

1 files changed, 1 insertions, 0 deletions

diff --git a/ruy/frontend.cc b/ruy/frontend.cc
index 58a8538..01ee474 100644
--- a/ruy/frontend.cc
+++ b/ruy/frontend.cc
@@ -23,6 +23,7 @@ limitations under the License.
 namespace ruy {
 
 void MulFrontEndFromTrMulParams(Ctx* ctx, TrMulParams* params) {
+  RUY_TRACE_SCOPE;
   // Handle Matrix::cache_policy, possibly retrieving existing packed matrices
   // or packing and caching now.
   PreparePackedMatrices(ctx, params);