[XLA:GPU] Enable int4 matmul rewriting with Triton MLIR rewriter by default.

PiperOrigin-RevId: 715341409

Author: loislo

xla/debug_options_flags.cc

@@ -232,7 +232,7 @@ DebugOptions DefaultDebugOptionsIgnoringFlags() {
   opts.set_xla_gpu_exhaustive_tiling_search(false);
 
   opts.set_xla_gpu_experimental_enable_triton_heroless_priority_fusion(false);
-  opts.set_xla_gpu_experimental_enable_triton_i4_rewrites(false);
+  opts.set_xla_gpu_experimental_enable_triton_i4_rewrites(true);
 
   opts.set_xla_gpu_auto_spmd_partitioning_memory_budget_gb(0);
   opts.set_xla_gpu_auto_spmd_partitioning_memory_budget_ratio(1.1);

xla/service/gpu/fusions/triton/triton_fusion_emitter_int4_device_test.cc

@@ -377,13 +377,6 @@ TEST_F(TritonTest, NonstandardLayoutInt4) {
   )";
 
   TF_ASSERT_OK_AND_ASSIGN(auto module, GetOptimizedModule(kHloText));
-  EXPECT_TRUE(*RunFileCheck(module->ToString(), R"(
-           CHECK:  %[[param_0:.*]] = s4[64,128]{0,1:E(4)} parameter(0)
-           CHECK:  %[[bitcast:.*]] = s4[128,64]{1,0:E(4)} bitcast(s4[64,128]{0,1:E(4)} %[[param_0]])
-           CHECK:  %[[convert:.*]] = bf16[128,64]{1,0} convert(s4[128,64]{1,0:E(4)} %[[bitcast]])
-           CHECK:  %[[param_1:.*]] = bf16[256,64]{1,0} parameter(1)
-           CHECK:  ROOT %dot.1 = bf16[128,256]{1,0} dot(bf16[128,64]{1,0} %[[convert]], bf16[256,64]{1,0} %[[param_1]]), lhs_contracting_dims={1}, rhs_contracting_dims={1}
-  )"));
   EXPECT_TRUE(RunAndCompare(kHloText, ErrorSpec{/*aabs=*/1e-3, /*arel=*/1e-3}));
 }