build_tools/bazel/iree_bitcode_library.bzl

# Copyright 2023 The IREE Authors
#
# Licensed under the Apache License v2.0 with LLVM Exceptions.
# See https://llvm.org/LICENSE.txt for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

"""Rules for compiling with clang to produce bitcode libraries."""

def iree_arch_to_llvm_arch(
        iree_arch = None):
    """Converts an IREE_ARCH value to the corresponding LLVM arch name.

    Similar to the CMake function with the same name.

    Args:
        iree_arch: IREE_ARCH string value.

    Returns:
        The LLVM name for that architecture (first component of target triple).
    """

    if not iree_arch:
        return None
    if iree_arch == "arm_64":
        return "aarch64"
    if iree_arch == "arm_32":
        return "arm"
    if iree_arch == "x86_64":
        return "x86_64"
    if iree_arch == "x86_32":
        return "i386"
    if iree_arch == "riscv_64":
        return "riscv64"
    if iree_arch == "riscv_32":
        return "riscv32"
    if iree_arch == "wasm_64":
        return "wasm64"
    if iree_arch == "wasm_32":
        return "wasm32"
    fail("Unhandled IREE_ARCH value %s" % iree_arch)

def iree_bitcode_library(
        name,
        arch,
        srcs,
        internal_hdrs = [],
        copts = [],
        out = None,
        **kwargs):
    """Builds an LLVM bitcode library from an input file via clang.

    Args:
        name: Name of the target.
        arch: Target architecture to compile for, in IREE_ARCH format.
        srcs: source files to pass to clang.
        internal_hdrs: all headers transitively included by the source files.
                       Unlike typical Bazel `hdrs`, these are not exposed as
                       interface headers. This would normally be part of `srcs`,
                       but separating it was easier for `bazel_to_cmake`, as
                       CMake does not need this, and making this explicitly
                       Bazel-only allows using `filegroup` on the Bazel side.
        copts: additional flags to pass to clang.
        out: output file name (defaults to name.bc).
        **kwargs: any additional attributes to pass to the underlying rules.
    """

    clang_tool = "@llvm-project//clang:clang"
    link_tool = "@llvm-project//llvm:llvm-link"
    builtin_headers_dep = "@llvm-project//clang:builtin_headers_gen"
    builtin_headers_path = "external/llvm-project/clang/staging/include/"

    base_copts = [
        # Target architecture
        "-target",
        iree_arch_to_llvm_arch(arch),

        # C17 with no system deps.
        "-std=c17",
        "-nostdinc",
        "-ffreestanding",

        # Optimized and unstamped.
        "-O3",
        "-DNDEBUG",
        "-fno-ident",
        "-fdiscard-value-names",

        # Set the size of wchar_t to 4 bytes (instead of 2 bytes).
        # This must match what the runtime is built with.
        "-fno-short-wchar",

        # Enable inline asm.
        "-fasm",

        # Object file only in bitcode format:
        "-c",
        "-emit-llvm",

        # Force the library into standalone mode (not depending on build-directory
        # configuration).
        "-DIREE_DEVICE_STANDALONE=1",
    ]

    if arch == "arm_32":
        # Silence "warning: unknown platform, assuming -mfloat-abi=soft"
        base_copts.append("-mfloat-abi=soft")
    elif arch == "riscv_32":
        # On RISC-V, linking LLVM modules requires matching target-abi.
        # https://lists.llvm.org/pipermail/llvm-dev/2020-January/138450.html
        # The choice of ilp32d is simply what we have in existing riscv_32 tests.
        # Open question - how do we scale to supporting all RISC-V ABIs?
        base_copts.append("-mabi=ilp32d")
    elif arch == "riscv_64":
        # Same comments as above riscv_32 case.
        base_copts.append("-mabi=lp64d")

    bitcode_files = []
    for src in srcs:
        bitcode_out = "%s_%s.bc" % (name, src)
        bitcode_files.append(bitcode_out)
        native.genrule(
            name = "gen_%s" % (bitcode_out),
            srcs = [src, builtin_headers_dep] + internal_hdrs,
            outs = [bitcode_out],
            cmd = " && ".join([
                " ".join([
                    "$(location %s)" % (clang_tool),
                    "-isystem $(BINDIR)/%s" % builtin_headers_path,
                    " ".join(base_copts + copts),
                    " ".join(["-I $(BINDIR)/runtime/src"]),
                    " ".join(["-I runtime/src"]),
                    "-o $(location %s)" % (bitcode_out),
                    "$(location %s)" % (src),
                ]),
            ]),
            tools = [
                clang_tool,
            ],
            message = "Compiling %s to %s..." % (src, bitcode_out),
            output_to_bindir = 1,
            **kwargs
        )

    if not out:
        out = "%s.bc" % (name)

    native.genrule(
        name = name,
        srcs = bitcode_files,
        outs = [out],
        cmd = " && ".join([
            " ".join([
                "$(location %s)" % (link_tool),
                "-o $(location %s)" % (out),
                " ".join(["$(locations %s)" % (src) for src in bitcode_files]),
            ]),
        ]),
        tools = [link_tool],
        message = "Linking bitcode library %s to %s..." % (name, out),
        output_to_bindir = 1,
        **kwargs
    )

def iree_cuda_bitcode_library(
        name,
        cuda_arch,
        srcs,
        internal_hdrs = [],
        copts = [],
        out = None,
        **kwargs):
    """Builds an LLVM bitcode library for CUDA from an input file via clang.

    Args:
        name: Name of the target.
        cuda_arch: Target sm architecture to compile for.
        srcs: source files to pass to clang.
        internal_hdrs: all headers transitively included by the source files.
                       Unlike typical Bazel `hdrs`, these are not exposed as
                       interface headers. This would normally be part of `srcs`,
                       but separating it was easier for `bazel_to_cmake`, as
                       CMake does not need this, and making this explicitly
                       Bazel-only allows using `filegroup` on the Bazel side.
        copts: additional flags to pass to clang.
        out: output file name (defaults to name.bc).
        **kwargs: any additional attributes to pass to the underlying rules.
    """

    clang_tool = "@llvm-project//clang:clang"
    link_tool = "@llvm-project//llvm:llvm-link"
    builtin_headers_dep = "@llvm-project//clang:builtin_headers_gen"
    builtin_headers_path = "external/llvm-project/clang/staging/include/"

    base_copts = [
        "-x",
        "cuda",

        # Target architecture
        "--cuda-gpu-arch=%s" % (cuda_arch),

        # Suppress warnings
        "-Wno-unknown-cuda-version",
        "-nocudalib",
        "--cuda-device-only",

        # Optimized.
        "-O3",

        # Object file only in bitcode format:
        "-c",
        "-emit-llvm",
    ]

    bitcode_files = []
    for src in srcs:
        bitcode_out = "%s_%s.bc" % (name, src)
        bitcode_files.append(bitcode_out)
        native.genrule(
            name = "gen_%s" % (bitcode_out),
            srcs = [src, builtin_headers_dep] + internal_hdrs,
            outs = [bitcode_out],
            cmd = " && ".join([
                " ".join([
                    "$(location %s)" % (clang_tool),
                    " ".join(base_copts + copts),
                    "-o $(location %s)" % (bitcode_out),
                    "$(location %s)" % (src),
                ]),
            ]),
            tools = [
                clang_tool,
            ],
            message = "Compiling %s to %s..." % (src, bitcode_out),
            output_to_bindir = 1,
            **kwargs
        )

    if not out:
        out = "%s.bc" % (name)

    native.genrule(
        name = name,
        srcs = bitcode_files,
        outs = [out],
        cmd = " && ".join([
            " ".join([
                "$(location %s)" % (link_tool),
                "-o $(location %s)" % (out),
                " ".join(["$(locations %s)" % (src) for src in bitcode_files]),
            ]),
        ]),
        tools = [link_tool],
        message = "Linking bitcode library %s to %s..." % (name, out),
        output_to_bindir = 1,
        **kwargs
    )

def iree_link_bitcode(
        name,
        bitcode_files,
        out = None,
        link_tool = "@llvm-project//llvm:llvm-link",
        **kwargs):
    """Builds an LLVM bitcode library from an input file via clang.

    Args:
        name: Name of the target.
        bitcode_files: bitcode files to link together.
        out: output file name (defaults to name.bc).
        link_tool: llvm-link tool used for linking bitcode files.
        **kwargs: any additional attributes to pass to the underlying rules.
    """

    bitcode_files_qualified = [("//" + native.package_name() + b) if b.startswith(":") else ("//" + native.package_name() + "/" + b) if b.count(":") else b for b in bitcode_files]

    if not out:
        out = "%s.bc" % (name)
    native.genrule(
        name = name,
        srcs = bitcode_files_qualified,
        outs = [out],
        cmd = " && ".join([
            " ".join([
                "$(location %s)" % (link_tool),
                "-o $(location %s)" % (out),
                " ".join(["$(locations %s)" % (src) for src in bitcode_files_qualified]),
            ]),
        ]),
        tools = [link_tool],
        message = "Linking bitcode library %s to %s..." % (name, out),
        output_to_bindir = 1,
        **kwargs
    )