table of contents
llvm-remark-size-diff - diff size remarks
llvm-remark-size-diff [options] file_a file_b –parser parser
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 optimization settings.
llvm-remark-size-diff handles both YAML and bitstream remarks.
- Select the type of input remark parser. Required. * yaml: The tool will parse YAML remarks. * bitstream: The tool will parse bitstream remarks.
- Output style. * human: Human-readable textual report. Default option. * json: JSON report.
- Pretty-print JSON output. Optional.
If output is not set to JSON, this does nothing.
- Output file for the report. Outputs to stdout by default.
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 instructions in the second file.
- >: More instructions in second file than first file.
- <: Fewer instructions in second file than in first file.
- 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.
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%)
- Sum of all instruction count changes between the second and first file.
- Percent increase or decrease in instruction count between the second and first file.
- Sum of all stack byte count changes between the second and first file.
- Percent increase or decrease in stack byte usage between the second and first file.
Suppose we are comparing two files, OLD and NEW.
llvm-remark-size-diff will output JSON as follows.
"B": "path/to/NEW" ] "InBoth": [
... ], "OnlyInA": [
... ], "OnlyInB": [
- Original paths to remark files.
- A: Path to the first file.
- B: Path to the second file.
The InBoth, OnlyInA, and OnlyInB sections contain size information for each function in the input remark files.
"FunctionName" : "function_name"
- Name of the function.
- Instruction counts for the function.
- INST_COUNT_A: Instruction count in OLD.
- INST_COUNT_B: Instruction count in NEW.
- 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 separately.
To compute the diffs:
- Instruction count diff: INST_COUNT_B - INST_COUNT_A
- Stack byte count diff: STACK_BYTES_B - STACK_BYTES_A
llvm-remark-size-diff returns 0 on success, and a non-zero value otherwise.
Maintained by the LLVM Team (https://llvm.org/).
2003-2023, LLVM Project