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Simplified BranchProbabilityInfo demo

bpi.cpp reimplements the estimated (loop-aware) heuristic of LLVM's BranchProbabilityInfo — the only heuristic that is a pure function of the CFG + loop structure. See the header comment in bpi.cpp for what is intentionally omitted (instruction-level heuristics, computeUnlikelySuccessors).

Loops come from a nested cycle forest built with Tao Wei's single-pass DFS (the algorithm llvm::CycleInfo uses), visiting successors LIFO to match LLVM's iterative DFS order. This handles reducible and irreducible loops and gives each

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// Havlak-Tarjan loop-nesting-forest algorithm, self-contained.
//
// Two passes over the CFG: (1) a DFS spanning tree recording preorder and finish
// times, then (2) candidate headers in reverse preorder, each flood-filling its
// loop body backward through predecessors, with a UNION-FIND collapse of the
// already-formed inner loops. Each loop tracks its ENTRY set, so absorbing an
// irreducible multi-entry subloop re-examines the predecessors of ALL its
// entries -- pulling in the outer nodes that reach it through a non-header
// entry. It builds the same loop-nesting forest as the single-pass wei.cpp and
// as llvm/include/llvm/ADT/GenericCycleImpl.h.

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// ============================================================================
//  Squarebound · 方格征途
//  —— 致童年：在五子棋盘上，用黑白棋子与四色标识摆出的战棋梦。
//
//  绿子=主角  蓝/红/黄=英雄  白子正面=我方小兵  白子反面=敌方小兵  黑子=障碍
//  15x15 棋盘（五子棋规格，含星位）。英雄血量以二进制棋子展示（致敬）。
//
//  操作：左键 选择/移动/攻击   右键 待命/取消   空格 结束回合(敌方回合按住加速)
//        Shift+F1~F9 存档     F1~F9 读档       Esc 取消选择/返回标题
// ============================================================================

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Alan Modra - Code Review Style
===============================

Role: Long-time GNU binutils maintainer, GNU ld (BFD linker), PowerPC backend

Deep institutional knowledge
- Decades of binutils/ld experience
- Knows the history behind obscure design decisions
- Understands BFD internals better than anyone

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#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <numeric>
#include <random>
#include <vector>
using namespace std;

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#include <assert.h>
#include <inttypes.h>
#include <stdbit.h>
#include <stdio.h>
#include <string.h>

/*
Big-endian prefix varint encoding for 64-bit integers.

The first byte determines the total length using most significant bits.

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#include <assert.h>
#include <stdbit.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

/*
little-endian suffix varint

xxxxxxx1:      7 value bits, 1 byte

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#!/usr/bin/env ruby
# This program downloads and builds several compression utilities, benchmarks their compression and decompression
# performance on a specific input file including memory consumption, and finally generates HTML charts.
require 'benchmark'
require 'digest'
require 'etc'
require 'fileutils'
require 'json'
require 'net/http'
require 'optparse'

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Aug 23 10:58:15 blitz kernel: Linux version 6.16.1-arch1-1 (linux@archlinux) (gcc (GCC) 15.2.1 20250813, GNU ld (GNU Binutils) 2.45.0) #1 SMP PREEMPT_DYNAMIC Fri, 15 Aug 2025 16:04:43 +0000
Aug 23 10:58:15 blitz kernel: Command line: BOOT_IMAGE=/vmlinuz-linux root=/dev/nvme0n1p3
Aug 23 10:58:15 blitz kernel: x86/CPU: Model not found in latest microcode list
Aug 23 10:58:15 blitz kernel: x86/split lock detection: #AC: crashing the kernel on kernel split_locks and warning on user-space split_locks
Aug 23 10:58:15 blitz kernel: BIOS-provided physical RAM map:
Aug 23 10:58:15 blitz kernel: BIOS-e820: [mem 0x0000000000000000-0x000000000009efff] usable
Aug 23 10:58:15 blitz kernel: BIOS-e820: [mem 0x000000000009f000-0x00000000000fffff] reserved
Aug 23 10:58:15 blitz kernel: BIOS-e820: [mem 0x0000000000100000-0x000000005df8afff] usable
Aug 23 10:58:15 blitz kernel: BIOS-e820: [mem 0x000000005df8b000-0x000000005e88afff] reserved
Aug 23 10:58:15 blitz kernel: BIOS-e820: [mem 0x000000005e88b000-0x00000000606befff] usab