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59 lines
1.7 KiB
ReStructuredText
59 lines
1.7 KiB
ReStructuredText
llvm-exegesis - LLVM Machine Instruction Benchmark
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==================================================
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SYNOPSIS
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--------
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:program:`llvm-exegesis` [*options*]
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DESCRIPTION
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-----------
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:program:`llvm-exegesis` is a benchmarking tool that uses information available
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in LLVM to measure host machine instruction characteristics like latency or port
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decomposition.
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Given an LLVM opcode name and a benchmarking mode, :program:`llvm-exegesis`
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generates a code snippet that makes execution as serial (resp. as parallel) as
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possible so that we can measure the latency (resp. uop decomposition) of the
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instruction.
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The code snippet is jitted and executed on the host subtarget. The time taken
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(resp. resource usage) is measured using hardware performance counters. The
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result is printed out as YAML to the standard output.
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The main goal of this tool is to automatically (in)validate the LLVM's TableDef
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scheduling models.
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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:: -opcode-index=<LLVM opcode index>
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Specify the opcode to measure, by index.
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Either `opcode-index` or `opcode-name` must be set.
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.. option:: -opcode-name=<LLVM opcode name>
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Specify the opcode to measure, by name.
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Either `opcode-index` or `opcode-name` must be set.
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.. option:: -benchmark-mode=[Latency|Uops]
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Specify which characteristic of the opcode to measure.
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.. option:: -num-repetitions=<Number of repetition>
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Specify the number of repetitions of the asm snippet.
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Higher values lead to more accurate measurements but lengthen the benchmark.
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EXIT STATUS
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-----------
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:program:`llvm-exegesis` returns 0 on success. Otherwise, an error message is
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printed to standard error, and the tool returns a non 0 value.
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