vllm.compilation.passes.fusion.act_quant_fusion ¶

class ActivationQuantFusionPass(VllmPatternMatcherPass):
    """
    This pass fuses a pre-defined set of custom ops into fused ops.
    It uses the torch pattern matcher to find the patterns and replace them.

    Because patterns can only be registered once, the pass is a singleton.
    This will be addressed in a future version of PyTorch:
    https://github.com/pytorch/pytorch/pull/139321#issuecomment-2452354980
    """

    @enable_fake_mode
    def __init__(self, config: VllmConfig) -> None:
        super().__init__(config)

        self.patterns: PatternMatcherPass = PatternMatcherPass(
            pass_name="activation_quant_fusion_pass"
        )

        pattern_silu_mul_fp8 = SiluMulFp8StaticQuantPattern()
        pattern_silu_mul_fp8.register(self.patterns)

        if silu_and_mul_nvfp4_quant_supported:
            pattern_silu_mul_nvfp4 = SiluMulNvfp4QuantPattern()
            pattern_silu_mul_nvfp4.register(self.patterns)

        self.dump_patterns(config, self.patterns)

    @VllmInductorPass.time_and_log
    def __call__(self, graph: torch.fx.Graph) -> None:
        self.matched_count = self.patterns.apply(graph)
        logger.debug("Replaced %s patterns", self.matched_count)

    def uuid(self) -> str:
        return VllmInductorPass.hash_source(
            self,
            ActivationQuantPattern,
            SiluMulFp8StaticQuantPattern,
            SiluMulNvfp4QuantPattern,
        )

class ActivationQuantPattern(ABC):
    """
    The base class for Activation+Quant fusions.
    Should not be used directly.
    """

    def __init__(
        self,
        quant_key: QuantKey,
    ) -> None:
        self.quant_key = quant_key
        self.quant_dtype = quant_key.dtype

        assert self.quant_key in QUANT_OPS, (
            f"unsupported quantization scheme {self.quant_key}"
        )
        self.QUANT_OP = QUANT_OPS[self.quant_key]

        assert self.quant_key in FUSED_OPS, (
            f"unsupported fusion scheme {self.quant_key}"
        )
        self.FUSED_OP = FUSED_OPS[self.quant_key]

        self.silu_and_mul_matcher = MatcherSiluAndMul()

    def empty_quant(self, *args: Any, **kwargs: Any) -> torch.Tensor:
        kwargs = {"dtype": self.quant_dtype, "device": "cuda", **kwargs}
        return torch.empty(*args, **kwargs)

    @abstractmethod
    def register(self, pm_pass: PatternMatcherPass) -> None:
        raise NotImplementedError

class SiluMulFp8StaticQuantPattern(ActivationQuantPattern):
    """
    Fusion for SiluMul+Fp8StaticQuant Pattern
    """

    def __init__(self) -> None:
        super().__init__(kFp8StaticTensorSym)
        self.quant_matcher = MatcherQuantFP8(kFp8StaticTensorSym)

    def get_inputs(self) -> list[torch.Tensor]:
        scale = self.quant_matcher.inputs()[1]
        return [
            *self.silu_and_mul_matcher.inputs(),  # input
            scale,
        ]

    def register(self, pm_pass: PatternMatcherPass) -> None:
        def pattern(
            input: torch.Tensor,
            scale: torch.Tensor,
        ) -> torch.Tensor:
            result_silu_mul = self.silu_and_mul_matcher(input)
            result_quant = self.quant_matcher(result_silu_mul, scale)
            return result_quant[0]

        def replacement(
            input: torch.Tensor,
            scale: torch.Tensor,
        ) -> torch.Tensor:
            d = input.shape[-1] // 2
            output_shape = input.shape[:-1] + (d,)
            result = torch.empty(
                output_shape, device=input.device, dtype=self.quant_dtype
            )
            at = auto_functionalized(
                self.FUSED_OP, result=result, input=input, scale=scale
            )
            return at[1]

        inps = self.get_inputs()
        pattern(*inps)

        register_replacement(pattern, replacement, inps, fwd_only, pm_pass)

class SiluMulNvfp4QuantPattern(ActivationQuantPattern):
    """
    Fusion for SiluMul+Nvfp4Quant Pattern
    """

    def __init__(self) -> None:
        super().__init__(kNvfp4Dynamic)

    def get_inputs(self) -> list[torch.Tensor]:
        result = self.empty_quant(5, 32)
        output_scale = empty_i32(128, 4)
        input_ = empty_bf16(5, 64)
        scale = empty_fp32(1, 1)
        return [result, output_scale, input_, scale]

    def register(self, pm_pass: PatternMatcherPass) -> None:
        def pattern(
            result: torch.Tensor,
            output_scale: torch.Tensor,
            input: torch.Tensor,
            scale: torch.Tensor,
        ) -> tuple[torch.Tensor, torch.Tensor]:
            result_silu_mul = self.silu_and_mul_matcher(input)
            at = auto_functionalized(
                self.QUANT_OP,
                output=result,
                input=result_silu_mul,
                output_scale=output_scale,
                input_scale=scale,
                is_sf_swizzled_layout=True,
            )
            return at[1], at[2]

        def replacement(
            result: torch.Tensor,
            output_scale: torch.Tensor,
            input: torch.Tensor,
            scale: torch.Tensor,
        ) -> tuple[torch.Tensor, torch.Tensor]:
            at = auto_functionalized(
                self.FUSED_OP,
                result=result,
                result_block_scale=output_scale,
                input=input,
                input_global_scale=scale,
            )
            return at[1], at[2]

        register_replacement(pattern, replacement, self.get_inputs(), fwd_only, pm_pass)