llvm-bcanalyzer - LLVM bytecode analyzer

llvm-bcanalyzer [options] [filename]

The llvm-bcanalyzer command is a small utility for analyzing bytecode files. The tool reads a bytecode file (such as generated with the llvm-as tool) and produces a statistical report on the contents of the byteocde file. The tool will also dump a low level but human readable version of the bytecode file. This tool is probably not of much interest or utility except for those working directly with the bytecode file format. Most LLVM users can just ignore this tool.

If filename is omitted or is CW-, then llvm-bcanalyzer reads its input from standard input. This is useful for combining the tool into a pipeline.

Output is written to the standard output.

-nodetails

Causes llvm-bcanalyzer to abbreviate its output by writing out only a module level summary. The details for individual functions are not displayed.

-dump

Causes llvm-bcanalyzer to dump the bytecode in a human readable format. This format is significantly different from LLVM assembly and provides details about the encoding of the bytecode file.

-verify

Causes llvm-bcanalyzer to verify the module produced by by reading the bytecode. This ensures that the statistics generated are based on a consistent module.

--help

Print a summary of command line options.

If llvm-bcanalyzer succeeds, it will exit with 0. Otherwise, if an error occurs, it will exit with a non-zero value, usually 1.

The following items are always printed by llvm-bcanalyzer. They comprize the summary output.

Bytecode Analysis Of Module

This just provides the name of the module for which bytecode analysis is being generated.

Bytecode Version Number

The bytecode version (not LLVM version) of the file read by the analyzer.

File Size

The size, in bytes, of the entire bytecode file.

Module Bytes

The size, in bytes, of the module block. Percentage is relative to File Size.

Function Bytes

The size, in bytes, of all the function blocks. Percentage is relative to File Size.

Global Types Bytes

The size, in bytes, of the Global Types Pool. Percentage is relative to File Size. This is the size of the definitions of all types in the bytecode file.

Constant Pool Bytes

The size, in bytes, of the Constant Pool Blocks Percentage is relative to File Size.

Module Globals Bytes

Ths size, in bytes, of the Global Variable Definitions and their initializers. Percentage is relative to File Size.

Instruction List Bytes

The size, in bytes, of all the instruction lists in all the functions. Percentage is relative to File Size. Note that this value is also included in the Function Bytes.

Compaction Table Bytes

The size, in bytes, of all the compaction tables in all the functions. Percentage is relative to File Size. Note that this value is also included in the Function Bytes.

Compaction Table Bytes

The size, in bytes, of all the symbol tables in all the functions. Percentage is relative to File Size. Note that this value is also included in the Function Bytes.

Dependent Libraries Bytes

The size, in bytes, of the list of dependent libraries in the module. Percentage is relative to File Size. Note that this value is also included in the Module Global Bytes.

Number Of Bytecode Blocks

The total number of blocks of any kind in the bytecode file.

Number Of Functions

The total number of function definitions in the bytecode file.

Number Of Types

The total number of types defined in the Global Types Pool.

Number Of Constants

The total number of constants (of any type) defined in the Constant Pool.

Number Of Basic Blocks

The total number of basic blocks defined in all functions in the bytecode file.

Number Of Instructions

The total number of instructions defined in all functions in the bytecode file.

Number Of Long Instructions

The total number of long instructions defined in all functions in the bytecode file. Long instructions are those taking greater than 4 bytes. Typically long instructions are GetElementPtr with several indices, PHI nodes, and calls to functions with large numbers of arguments.

Number Of Operands

The total number of operands used in all instructions in the bytecode file.

Number Of Compaction Tables

The total number of compaction tables in all functions in the bytecode file.

Number Of Symbol Tables

The total number of symbol tables in all functions in the bytecode file.

Number Of Dependent Libs

The total number of dependent libraries found in the bytecode file.

Total Instruction Size

The total size of the instructions in all functions in the bytecode file.

Average Instruction Size

The average number of bytes per instruction across all functions in the bytecode file. This value is computed by dividing Total Instruction Size by Number Of Instructions.

Maximum Type Slot Number

The maximum value used for a type's slot number. Larger slot number values take more bytes to encode.

Maximum Value Slot Number

The maximum value used for a value's slot number. Larger slot number values take more bytes to encode.

Bytes Per Value

The average size of a Value definition (of any type). This is computed by dividing File Size by the total number of values of any type.

Bytes Per Global

The average size of a global definition (constants and global variables).

Bytes Per Function

The average number of bytes per function definition. This is computed by dividing Function Bytes by Number Of Functions.

# of VBR 32-bit Integers

The total number of 32-bit integers encoded using the Variable Bit Rate encoding scheme.

# of VBR 64-bit Integers

The total number of 64-bit integers encoded using the Variable Bit Rate encoding scheme.

# of VBR Compressed Bytes

The total number of bytes consumed by the 32-bit and 64-bit integers that use the Variable Bit Rate encoding scheme.

# of VBR Expanded Bytes

The total number of bytes that would have been consumed by the 32-bit and 64-bit integers had they not been compressed with the Variable Bit Rage encoding scheme.

Bytes Saved With VBR

The total number of bytes saved by using the Variable Bit Rate encoding scheme. The percentage is relative to # of VBR Expanded Bytes.

The following definitions occur only if the -nodetails option was not given. The detailed output provides additional information on a per-function basis.

Type

The type signature of the function.

Byte Size

The total number of bytes in the function's block.

Basic Blocks

The number of basic blocks defined by the function.

Instructions

The number of instructions defined by the function.

Long Instructions

The number of instructions using the long instruction format in the function.

Operands

The number of operands used by all instructions in the function.

Instruction Size

The number of bytes consumed by instructions in the function.

Average Instruction Size

The average number of bytes consumed by the instructions in the funtion. This value is computed by dividing Instruction Size by Instructions.

Bytes Per Instruction

The average number of bytes used by the function per instruction. This value is computed by dividing Byte Size by Instructions. Note that this is not the same as Average Instruction Size. It computes a number relative to the total function size not just the size of the instruction list.

# of VBR 32-bit Integers

The total number of 32-bit integers found in this function (for any use).

# of VBR 64-bit Integers

The total number of 64-bit integers found in this function (for any use).

# of VBR Compressed Bytes

The total number of bytes in this function consumed by the 32-bit and 64-bit integers that use the Variable Bit Rate encoding scheme.

# of VBR Expanded Bytes

The total number of bytes in this function that would have been consumed by the 32-bit and 64-bit integers had they not been compressed with the Variable Bit Rate encoding scheme.

Bytes Saved With VBR

The total number of bytes saved in this function by using the Variable Bit Rate encoding scheme. The percentage is relative to # of VBR Expanded Bytes.

llvm-dis, <http://llvm.cs.uiuc.edu/docs/BytecodeFormat.html>

Maintained by the LLVM Team (<http://llvm.cs.uiuc.edu>).