Add more numbers about MLIR binary sizes with the example binaries (NFC)

Author: joker-eph

mlir/examples/minimal-opt/README.md

@@ -3,12 +3,48 @@
 This folder contains example of minimal MLIR setup that can showcase the
 intended binary footprint of the framework.
 
-- mlir-cat: ~2MB
-  This includes the Core IR, the builtin dialect, the textual parser/printer,
-  the support for bytecode serialization.
-- mlir-minimal-opt: ~3MB
-  This adds all the tooling for an mlir-opt tool: the pass infrastructure
-  and all the instrumentation associated with it.
-- mlir-miminal-opt-canonicalize: ~4.8MB
-  This add the canonicalizer pass, which pulls in all the pattern/rewrite
-  machinery, including the PDL compiler and intepreter.
+- mlir-cat: This includes the Core IR, the builtin dialect, the textual
+  parser/printer, the support for bytecode serialization.
+- mlir-minimal-opt: This adds all the tooling for an mlir-opt tool: the pass
+  infrastructure and all the instrumentation associated with it.
+- mlir-miminal-opt-canonicalize: This add the canonicalizer pass, which pulls in
+  all the pattern/rewrite machinery, including the PDL compiler and intepreter.
+
+Below are some example measurements taken at the time of the LLVM 17 release,
+using clang-14 on a X86 Ubuntu and [bloaty](https://github.com/google/bloaty).
+
+|                                  | Base   | Os     | Oz     | Os LTO | Oz LTO |
+| :------------------------------: | ------ | ------ | ------ | ------ | ------ |
+| `mlit-cat`                       | 1018kB | 836KB  | 879KB  | 697KB  | 649KB  |
+| `mlir-minimal-opt`               | 1.54MB | 1.25MB | 1.29MB | 1.10MB | 1.00MB |
+| `mlir-minimal-opt-canonicalizer` | 2.24MB | 1.81MB | 1.86MB | 1.62MB | 1.48MB |
+
+Base configuration:
+
+```
+cmake ../llvm/ -G Ninja \
+   -DCMAKE_BUILD_TYPE=RelWithDebInfo \
+   -DLLVM_CCACHE_BUILD=ON \
+   -DLLVM_ENABLE_PROJECTS=mlir \
+   -DLLVM_BUILD_EXAMPLES=ON \
+   -DLLVM_TARGETS_TO_BUILD="Native" \
+   -DCMAKE_C_COMPILER=clang \
+   -DCMAKE_CXX_COMPILER=clang++ \
+   -DLLVM_ENABLE_LLD=ON \
+   -DLLVM_ENABLE_BACKTRACES=OFF \
+   -DCMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO=-Wl,-icf=all
+```
+
+Note: to measure the on-disk size, you need to run `strip bin/mlir-cat` first to
+remove all the debug info (which are useful for `bloaty` though).
+
+The optimization level can be tuned with `-Os` or `-Oz`:
+
+- `-DCMAKE_C_FLAGS_RELWITHDEBINFO="-Os -g -DNDEBUG" -DCMAKE_CXX_FLAGS_RELWITHDEBINFO="-Os -g -DNDEBUG"`
+- `-DCMAKE_C_FLAGS_RELWITHDEBINFO="-Oz -g -DNDEBUG" -DCMAKE_CXX_FLAGS_RELWITHDEBINFO="-Oz -g -DNDEBUG"`
+
+Finally LTO can also be enabled with `-DLLVM_ENABLE_LTO=FULL`.
+
+Bloaty can provide measurements using:
+`bloaty bin/mlir-cat -d compileunits --domain=vm` or
+`bloaty bin/mlir-cat -d symbols --demangle=full --domain=vm`