LLVM-REMARK-SIZE-DIFF(1) LLVM LLVM-REMARK-SIZE-DIFF(1)
NAME
llvm-remark-size-diff - diff size remarks
SYNOPSIS
llvm-remark-size-diff [options] file_a file_b –parser parser
DESCRIPTION
llvm-remark-size-diff diffs size remarks in two remark files: file_a
and file_b.
llvm-remark-size-diff can be used to gain insight into which functions
were impacted the most by code generation changes.
In most common use-cases file_a and file_b will be remarks output by
compiling a fixed source with differing compilers or differing opti-
mization settings.
llvm-remark-size-diff handles both YAML and bitstream remarks.
OPTIONS
--parser=<yaml|bitstream>
Select the type of input remark parser. Required. * yaml: The
tool will parse YAML remarks. * bitstream: The tool will parse
bitstream remarks.
--report-style=<human|json>
Output style. * human: Human-readable textual report. Default
option. * json: JSON report.
--pretty
Pretty-print JSON output. Optional.
If output is not set to JSON, this does nothing.
-o=<file>
Output file for the report. Outputs to stdout by default.
HUMAN-READABLE OUTPUT
The human-readable format for llvm-remark-size-diff is composed of two
sections:
• Per-function changes.
• A high-level summary of all changes.
Changed Function Section
Suppose you are comparing two remark files OLD and NEW.
For each function with a changed instruction count in OLD and NEW,
llvm-remark-size-diff will emit a line like below:
(++|--|==) (>|<) function_name, N instrs, M stack B
A breakdown of the format is below:
(++|--|==)
Which of OLD and NEW the function_name is present in.
• ++: Only in NEW. (“Added”)
• --: Only in OLD. (“Removed”)
• ==: In both.
(>|<) Denotes if function_name has more instructions or fewer instruc-
tions in the second file.
• >: More instructions in second file than first file.
• <: Fewer instructions in second file than in first file.
function_name
The name of the changed function.
N instrs
Second file instruction count - first file instruction count.
M stack B
Second file stack byte count - first file stack byte count.
Summary Section
llvm-remark-size-diff will output a high-level summary after printing
all changed functions.
instruction count: N (inst_pct_change%)
stack byte usage: M (sb_pct_change%)
N Sum of all instruction count changes between the second and
first file.
inst_pct_change%
Percent increase or decrease in instruction count between the
second and first file.
M Sum of all stack byte count changes between the second and first
file.
sb_pct_change%
Percent increase or decrease in stack byte usage between the
second and first file.
JSON OUTPUT
High-Level view
Suppose we are comparing two files, OLD and NEW.
llvm-remark-size-diff will output JSON as follows.
"Files": [
"A": "path/to/OLD",
"B": "path/to/NEW"
]
"InBoth": [
...
],
"OnlyInA": [
...
],
"OnlyInB": [
...
]
Files Original paths to remark files.
• A: Path to the first file.
• B: Path to the second file.
InBoth Functions present in both files.
OnlyInA
Functions only present in the first file.
OnlyInB
Functions only present in the second file.
Function JSON
The InBoth, OnlyInA, and OnlyInB sections contain size information for
each function in the input remark files.
{
"FunctionName" : "function_name"
"InstCount": [
INST_COUNT_A,
INST_COUNT_B
],
"StackSize": [
STACK_BYTES_A,
STACK_BYTES_B
],
}
FunctionName
Name of the function.
InstCount
Instruction counts for the function.
• INST_COUNT_A: Instruction count in OLD.
• INST_COUNT_B: Instruction count in NEW.
StackSize
Stack byte counts for the function.
• STACK_BYTES_A: Stack bytes in OLD.
• STACK_BYTES_B: Stack bytes in NEW.
Computing Diffs From Function JSON
Function JSON does not contain the diffs. Tools consuming JSON output
from llvm-remark-size-diff are responsible for computing the diffs sep-
arately.
To compute the diffs:
• Instruction count diff: INST_COUNT_B - INST_COUNT_A
• Stack byte count diff: STACK_BYTES_B - STACK_BYTES_A
EXIT STATUS
llvm-remark-size-diff returns 0 on success, and a non-zero value other-
wise.
AUTHOR
Maintained by the LLVM Team (https://llvm.org/).
COPYRIGHT
2003-2023, LLVM Project
15 2023-10-16 LLVM-REMARK-SIZE-DIFF(1)
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