[vLLM IR] 1/N Implement IR skeleton and rms_norm op (#33825)

Signed-off-by: Luka Govedič <lgovedic@redhat.com>
Signed-off-by: Xinyu Chen <xinyu1.chen@intel.com>
Signed-off-by: chzhang <chaojun.zhang@intel.com>
Signed-off-by: Luka Govedic <luka.govedic@gmail.com>
Co-authored-by: Xinyu Chen <xinyu1.chen@intel.com>
Co-authored-by: Chaojun Zhang <chaojun.zhang@intel.com>
Co-authored-by: Luka Govedič <ProExpertProg@h100-01.nemg-001.lab.rdu2.dc.redhat.com>

tests/test_config.py

@@ -6,12 +6,14 @@ import os
 from dataclasses import MISSING, Field, asdict, dataclass, field
 from unittest.mock import patch
 
+import pydantic
 import pytest
 from pydantic import ValidationError
 
 from vllm.compilation.backends import VllmBackend
 from vllm.config import (
     CompilationConfig,
+    KernelConfig,
     ModelConfig,
     ParallelConfig,
     PoolerConfig,
@@ -21,6 +23,7 @@ from vllm.config import (
     update_config,
 )
 from vllm.config.compilation import CompilationMode, CUDAGraphMode
+from vllm.config.kernel import IrOpPriorityConfig
 from vllm.config.load import LoadConfig
 from vllm.config.utils import get_field
 from vllm.config.vllm import (
@@ -1077,6 +1080,39 @@ def test_vllm_config_explicit_overrides():
     assert config.compilation_config.cudagraph_mode == CUDAGraphMode.FULL_AND_PIECEWISE
 
 
+def test_fusion_pass_op_priority():
+    """This test checks that custom op enablement & IR op priority
+    correctly control default fusions"""
+
+    # Default config, O2, rms_norm+quant fusion disabled
+    cfg1 = VllmConfig()
+    assert not cfg1.compilation_config.pass_config.fuse_norm_quant
+
+    # rms_norm manually enabled, O1, rms_norm+quant fusion enabled
+    cfg2 = VllmConfig(
+        optimization_level=OptimizationLevel.O1,
+        compilation_config=CompilationConfig(
+            custom_ops=["+rms_norm"],
+        ),
+    )
+    assert cfg2.compilation_config.pass_config.fuse_norm_quant
+
+    # using custom kernel for RMSNorm via IR:
+    # Note that vLLM IR only supports the non-residual rms_norm for now;
+    # soon this will be resolved.
+    cfg3 = VllmConfig(
+        kernel_config=KernelConfig(
+            ir_op_priority=IrOpPriorityConfig(rms_norm=["vllm_c"])
+        )
+    )
+    assert cfg3.compilation_config.pass_config.fuse_norm_quant
+
+    # block-fp8 model should enable quant_fp8 automatically
+    cfg4 = VllmConfig(model_config=ModelConfig("Qwen/Qwen3-4B-FP8"))
+    assert "+quant_fp8" in cfg4.compilation_config.custom_ops
+    assert cfg4.compilation_config.pass_config.fuse_norm_quant
+
+
 def test_scheduler_config_init():
     with pytest.raises(ValidationError):
         # Positional InitVars missing
@@ -1171,3 +1207,35 @@ def test_eagle_draft_model_config():
     assert draft_model_config.hf_text_config.model_type == "eagle"
     assert draft_model_config.architectures == ["EagleLlamaForCausalLM"]
     assert draft_model_config.architecture == "EagleLlamaForCausalLM"
+
+
+def test_ir_op_priority_default():
+    """Test that IR op priority defaults are set correctly."""
+    from vllm.config.kernel import IrOpPriorityConfig
+
+    # Assert default is applied to ops
+    priority_config = IrOpPriorityConfig.with_default(["vllm_c", "native"])
+    assert priority_config.rms_norm == ["vllm_c", "native"]
+
+    # Assert single ops override the default
+    assert IrOpPriorityConfig.with_default(
+        ["vllm_c", "native"], rms_norm=["oink", "native"]
+    ) == IrOpPriorityConfig(rms_norm=["oink", "native"])
+
+
+def test_ir_op_priority_str():
+    """Test that passing a comma-delimited string works"""
+    from vllm.config.kernel import IrOpPriorityConfig
+
+    priority_config = IrOpPriorityConfig(rms_norm="vllm_c")
+    assert priority_config.rms_norm == ["vllm_c"]
+
+    priority_config = IrOpPriorityConfig(rms_norm="vllm_c,native")
+    assert priority_config.rms_norm == ["vllm_c", "native"]
+
+    priority_config = IrOpPriorityConfig(rms_norm=" native, vllm_c ")
+    assert priority_config.rms_norm == ["native", "vllm_c"]
+
+    with pytest.raises(pydantic.ValidationError):
+        # must be list of only strings
+        priority_config = IrOpPriorityConfig(rms_norm=["vllm_c", 4, "native"])