Add a configuration option for code size.

This change adds a CPU-specific flag: xla_cpu_optimize_for_size

When this flag is passed, it changes the optimizers to run
more or less analogously to LLVM's -Os optimizations.

There are two things that turning on the code size optimization option
controls:
* the internal settings of some optimization passes (which is mostly
  controlled through a function attribute)
* the passes that get run (which is decided by the pass manager)

This change also refactors the code by reorganizing the way
that CPU backend specific flags are queried, as well as some
other minor refactoring.

PiperOrigin-RevId: 164218771

1 files changed, 14 insertions, 4 deletions

diff --git a/tensorflow/compiler/xla/service/cpu/disassembler.h b/tensorflow/compiler/xla/service/cpu/disassembler.h
index 4c03567ee6..b6feaa7e45 100644
--- a/tensorflow/compiler/xla/service/cpu/disassembler.h
+++ b/tensorflow/compiler/xla/service/cpu/disassembler.h
@@ -33,19 +33,29 @@ limitations under the License.
 namespace xla {
 namespace cpu {
 
+struct DisassemblerResult {
+  DisassemblerResult(const string& text, size_t code_size_bytes)
+      : text(text), code_size_bytes(code_size_bytes) {}
+
+  // The dissassembled text sections of the object file.
+  string text;
+  // The total number of bytes of executable code in the object file.
+  uint64_t code_size_bytes;
+};
+
 // Class for disassembling object files (and potentially other constructs) into
-// X86 assembly. Builds all the LLVM disassembly and instruction printing
+// x86/ARM assembly. Builds all the LLVM disassembly and instruction printing
 // constructs from a given TargetMachine.
 class Disassembler {
  public:
   explicit Disassembler(const llvm::TargetMachine& target_machine);
 
-  // Returns a string containing the disassembled text sections of the given
-  // object file.
+  // Returns a DisassemblerResult for the given object file, containing the
+  // disassembled code.
   //
   // If we couldnt' retrieve a disassembler for this platform, an error status
   // is returned.
-  StatusOr<string> DisassembleObjectFile(
+  StatusOr<DisassemblerResult> DisassembleObjectFile(
       const llvm::object::ObjectFile& object_file) const;
 
  private: