Implement arena allocator to reduce allocation

[ChAoSUnItY]

In this patch, by introducing arena allocator, also known as regional allocator, and optimizing calloc byte buffer clearing algorithm, the compiler's memory usage, page fault occurrence frequency, and performance are significantly improved. The resident set size has been reduced up to 2/3 ~ 1/2.

Arena allocator's introduction allows future development safely allocating structures without worrying their lifetime. This has already been implemented in SSA unit's "basic_block_t" allocation, which now doesn't require traversal to free up all connected detached basic blocks.

In addition, calloc's byte buffer clearing algorithm has been changed into bulk clearing algorithm, which clears up 4 bytes at a time when requested byte buffer's size is large enough.

Performance analysis for out/shecc src/main.c (built by GCC)

uftrace comparison

RSS comparison

/usr/bin/time -v ./out/shecc src/main.c:

        Command being timed: "./out/shecc src/main.c"
        User time (seconds): 0.28
        System time (seconds): 1.10
        Percent of CPU this job got: 94%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:01.46
        Average shared text size (kbytes): 0
        Average unshared data size (kbytes): 0
        Average stack size (kbytes): 0
        Average total size (kbytes): 0
        Maximum resident set size (kbytes): 758556
        Average resident set size (kbytes): 0
        Major (requiring I/O) page faults: 0
        Minor (reclaiming a frame) page faults: 188705
        Voluntary context switches: 0
        Involuntary context switches: 1
        Swaps: 0
        File system inputs: 0
        File system outputs: 464
        Socket messages sent: 0
        Socket messages received: 0
        Signals delivered: 0
        Page size (bytes): 4096
        Exit status: 0

/usr/bin/time -v ./out/shecc-opt src/main.c

        Command being timed: "./out/shecc-opt src/main.c"
        User time (seconds): 0.38
        System time (seconds): 0.31
        Percent of CPU this job got: 93%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.74
        Average shared text size (kbytes): 0
        Average unshared data size (kbytes): 0
        Average stack size (kbytes): 0
        Average total size (kbytes): 0
        Maximum resident set size (kbytes): 321748
        Average resident set size (kbytes): 0
        Major (requiring I/O) page faults: 0
        Minor (reclaiming a frame) page faults: 89749
        Voluntary context switches: 0
        Involuntary context switches: 1
        Swaps: 0
        File system inputs: 0
        File system outputs: 464
        Socket messages sent: 0
        Socket messages received: 0
        Signals delivered: 0
        Page size (bytes): 4096
        Exit status: 0

Performance analysis for out/shecc-stage1.elf src/main.c

RSS comparison

/usr/bin/time -v ./out/shecc-stage1.elf src/main.c:

        Command being timed: "./out/shecc-stage1.elf src/main.c"
        User time (seconds): 4.77
        System time (seconds): 3.61
        Percent of CPU this job got: 95%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:08.81
        Average shared text size (kbytes): 0
        Average unshared data size (kbytes): 0
        Average stack size (kbytes): 0
        Average total size (kbytes): 0
        Maximum resident set size (kbytes): 993232
        Average resident set size (kbytes): 0
        Major (requiring I/O) page faults: 0
        Minor (reclaiming a frame) page faults: 245225
        Voluntary context switches: 8
        Involuntary context switches: 20
        Swaps: 0
        File system inputs: 0
        File system outputs: 0
        Socket messages sent: 0
        Socket messages received: 0
        Signals delivered: 0
        Page size (bytes): 4096
        Exit status: 0

/usr/bin/time -v ./out/shecc-stage1-opt.elf src/main.c

        Command being timed: "./out/shecc-stage1-opt.elf src/main.c"
        User time (seconds): 4.67
        System time (seconds): 2.13
        Percent of CPU this job got: 94%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:07.20
        Average shared text size (kbytes): 0
        Average unshared data size (kbytes): 0
        Average stack size (kbytes): 0
        Average total size (kbytes): 0
        Maximum resident set size (kbytes): 658928
        Average resident set size (kbytes): 0
        Major (requiring I/O) page faults: 0
        Minor (reclaiming a frame) page faults: 161604
        Voluntary context switches: 5
        Involuntary context switches: 7
        Swaps: 0
        File system inputs: 0
        File system outputs: 464
        Socket messages sent: 0
        Socket messages received: 0
        Signals delivered: 0
        Page size (bytes): 4096
        Exit status: 0

Summary by Bito

This pull request introduces an arena allocator to enhance memory management, significantly reducing memory usage and improving performance. The calloc function has been optimized for bulk memory clearing, and several structures have been updated to utilize the new allocator. Unused functions have been removed for a cleaner codebase, and comprehensive documentation has been added.

Unit tests added: True

Estimated effort to review (1-5, lower is better): 2

[jserv]

Thank @ChAoSUnItY for contributing!