69cd746bd2
This patch adds a Clang-compatible -mtune option to llc, to enable decoupled ISA and microarchitecture targeting, which is especially important for backend development. For example, it can enable to easily test a subtarget feature or scheduling model effects on codegen across a variaty of workloads on the IR corpus benchmark: https://github.com/dtcxzyw/llvm-codegen-benchmark. The implementation adds an isolated generic codegen flag, to establish a base for wider usage - the plan is to add it to `opt` as well in a followup patch. Then `llc` consumes it, and sets `tune-cpu` attributes for functions, which are further consumed by the backend.
238 lines
6.7 KiB
ReStructuredText
238 lines
6.7 KiB
ReStructuredText
llc - LLVM static compiler
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==========================
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.. program:: llc
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SYNOPSIS
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--------
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:program:`llc` [*options*] [*filename*]
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DESCRIPTION
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-----------
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The :program:`llc` command compiles LLVM source inputs into assembly language
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for a specified architecture. The assembly language output can then be passed
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through a native assembler and linker to generate a native executable.
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The choice of architecture for the output assembly code is automatically
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determined from the input file, unless the :option:`-march` option is used to
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override the default.
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OPTIONS
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-------
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If ``filename`` is "``-``" or omitted, :program:`llc` reads from standard input.
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Otherwise, it will read from ``filename``. Inputs can be in either the LLVM
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assembly language format (``.ll``) or the LLVM bitcode format (``.bc``).
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If the :option:`-o` option is omitted, then :program:`llc` will send its output
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to standard output if the input is from standard input. If the :option:`-o`
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option specifies "``-``", then the output will also be sent to standard output.
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If no :option:`-o` option is specified and an input file other than "``-``" is
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specified, then :program:`llc` creates the output filename by taking the input
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filename, removing any existing ``.bc`` extension, and adding a ``.s`` suffix.
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Other :program:`llc` options are described below.
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End-user Options
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~~~~~~~~~~~~~~~~
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.. option:: -help
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Print a summary of command line options.
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.. option:: -M
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Pass target-specific InstPrinter options.
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Refer to the ``-M`` option of :manpage:`llvm-objdump(1)`.
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.. option:: -o <filename>
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Use ``<filename>`` as the output filename. See the summary above for more
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details.
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.. option:: -O=uint
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Generate code at different optimization levels. These correspond to the
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``-O0``, ``-O1``, ``-O2``, and ``-O3`` optimization levels used by
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:program:`clang`.
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.. option:: -mtriple=<target triple>
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Override the target triple specified in the input file with the specified
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string.
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.. option:: -march=<arch>
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Specify the architecture for which to generate assembly, overriding the target
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encoded in the input file. See the output of ``llc -help`` for a list of
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valid architectures. By default this is inferred from the target triple or
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autodetected to the current architecture.
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.. option:: -mcpu=<cpuname>
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Specify a specific chip in the current architecture to generate code for.
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By default this is inferred from the target triple and autodetected to
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the current architecture. For a list of available CPUs, use:
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.. code-block:: none
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llvm-as < /dev/null | llc -march=xyz -mcpu=help
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.. option:: -mtune=<cpuname>
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Specify a specific chip microarchitecture in the current architecture
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to tune code for. By default this is inferred from the target triple and
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autodetected to the current architecture. For a list of available tuning
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CPUs, use:
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.. code-block:: none
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llvm-as < /dev/null | llc -march=xyz -mtune=help
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.. option:: -filetype=<output file type>
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Specify what kind of output ``llc`` should generated. Options are: ``asm``
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for textual assembly ( ``'.s'``), ``obj`` for native object files (``'.o'``)
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and ``null`` for not emitting anything (for performance testing).
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Note that not all targets support all options.
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.. option:: -mattr=a1,+a2,-a3,...
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Override or control specific attributes of the target, such as whether SIMD
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operations are enabled or not. The default set of attributes is set by the
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current CPU. For a list of available attributes, use:
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.. code-block:: none
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llvm-as < /dev/null | llc -march=xyz -mattr=help
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.. option:: --frame-pointer
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Specify effect of frame pointer elimination optimization (all,non-leaf,none).
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.. option:: --disable-excess-fp-precision
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Disable optimizations that may produce excess precision for floating point.
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Note that this option can dramatically slow down code on some systems
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(e.g. X86).
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.. option:: --enable-no-infs-fp-math
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Enable optimizations that assume no Inf values.
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.. option:: --enable-no-nans-fp-math
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Enable optimizations that assume no NAN values.
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.. option:: --enable-no-signed-zeros-fp-math
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Enable FP math optimizations that assume the sign of 0 is insignificant.
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.. option:: --enable-no-trapping-fp-math
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Enable setting the FP exceptions build attribute not to use exceptions.
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.. option:: --stats
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Print statistics recorded by code-generation passes.
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.. option:: --save-stats, --save-stats=cwd, --save-stats=obj
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Save LLVM statistics to a file in the current directory
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(:option:`--save-stats`/"--save-stats=cwd") or the directory
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of the output file ("--save-stats=obj") in JSON format.
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.. option:: --time-passes
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Record the amount of time needed for each pass and print a report to standard
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error.
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.. option:: --load=<dso_path>
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Dynamically load ``dso_path`` (a path to a dynamically shared object) that
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implements an LLVM target. This will permit the target name to be used with
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the :option:`-march` option so that code can be generated for that target.
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.. option:: -meabi=[default|gnu|4|5]
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Specify which EABI version should conform to. Valid EABI versions are *gnu*,
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*4* and *5*. Default value (*default*) depends on the triple.
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.. option:: -stack-size-section
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Emit the .stack_sizes section which contains stack size metadata. The section
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contains an array of pairs of function symbol values (pointer size) and stack
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sizes (unsigned LEB128). The stack size values only include the space allocated
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in the function prologue. Functions with dynamic stack allocations are not
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included.
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.. option:: -remarks-section
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Emit the __remarks (MachO) section which contains metadata about remark
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diagnostics.
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Tuning/Configuration Options
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. option:: --print-after-isel
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Print generated machine code after instruction selection (useful for debugging).
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.. option:: --regalloc=<allocator>
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Specify the register allocator to use.
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Valid register allocators are:
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*basic*
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Basic register allocator.
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*fast*
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Fast register allocator. It is the default for unoptimized code.
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*greedy*
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Greedy register allocator. It is the default for optimized code.
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*pbqp*
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Register allocator based on 'Partitioned Boolean Quadratic Programming'.
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.. option:: --spiller=<spiller>
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Specify the spiller to use for register allocators that support it. Currently
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this option is used only by the linear scan register allocator. The default
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``spiller`` is *local*. Valid spillers are:
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*simple*
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Simple spiller
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*local*
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Local spiller
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Intel IA-32-specific Options
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. option:: --x86-asm-syntax=[att|intel]
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Specify whether to emit assembly code in AT&T syntax (the default) or Intel
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syntax.
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EXIT STATUS
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-----------
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If :program:`llc` succeeds, it will exit with 0. Otherwise, if an error
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occurs, it will exit with a non-zero value.
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SEE ALSO
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--------
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:manpage:`lli(1)`
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