add more ir opt code, clearified what to opt, so current opt code may need rewrite

StgSharp.RegularAnalysis/Text/RegexIR.cs

@@ -62,10 +62,13 @@ namespace StgSharp.RegularAnalysis.Text
     }
 
     internal sealed class RegexFindSeqIR(
-                          string pattern
+                          string pattern,
+                          bool isFirst
     ) : RegexIR
     {
 
+        public bool IsFirst { get; } = isFirst;
+
         public string Pattern { get; } = pattern;
 
         internal override RegexIRCommand Command => RegexIRCommand.Find_Seq;

StgSharp.RegularAnalysis/Text/RegexInterpreter.IROptimize.cs

@@ -28,6 +28,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Runtime.InteropServices;
 using System.Text;
 using System.Threading.Tasks;
 
@@ -36,19 +37,22 @@ namespace StgSharp.RegularAnalysis.Text
     public partial class RegexAnalyzer
     {
 
-        internal static RegexInfo ScanAndOptimizeIR(
+        // this array is not thread safe so opt process must be done in single thread.
+        private RegexIR[] _opt_buffer = new RegexIR[16];
+
+        internal RegexInfo ScanAndOptimizeIR(
                            List<RegexIR> baseIR,
                            out List<RegexIR> optIR
         )
         {
             int index = 0;
+            Span<RegexIR> origin_span = CollectionsMarshal.AsSpan(baseIR);
             List<RegexIR> optimizedIR = new(baseIR.Count);
             List<RegexIR> segment = [];
             RegexInfo info = new();
             do
             {
-                // TODO scan and opt here
-                OptimizeIR(baseIR, ref index, segment, info);
+                OptimizeIR(origin_span, ref index, segment, info);
                 optimizedIR.AddRange(segment);
                 index++;
             } while (index < baseIR.Count);
@@ -56,34 +60,103 @@ namespace StgSharp.RegularAnalysis.Text
             return info;
         }
 
-        private static void OptimizeDot(
+        private int ExpandCount(
+                    string pattern,
+                    int min,
+                    int max,
+                    bool is_greedy,
+                    in Span<RegexIR> span
+        )
+        {
+            // expand count operation to less cycles.
+
+            const int fast_seq_length = 32;
+
+            int fast_count = fast_seq_length / pattern.Length;
+            fast_count = int.Min(fast_count, min);
+            if (fast_count > 0)
+            {
+                string fast_pattern = string.Concat(Enumerable.Repeat(pattern, fast_count));
+
+                int fast_min = min / fast_count;
+                int consumed_count = fast_min * fast_count;
+                int remain_min = min - consumed_count;
+                int remain_max = max - consumed_count;
+                remain_max = int.Max(-1, remain_max);    //for negative stands for infinitive
+                if (remain_max == 0)
+                {
+                    // a{2}
+                    RegexCountSeqIR fast = new(fast_min, fast_min, is_greedy, fast_pattern);
+                    span[0] = fast;
+                    return 1;
+                } else
+                {
+                    // a{2,5}
+                    RegexCountSeqIR fast = new(fast_min, fast_min, is_greedy, fast_pattern);
+                    RegexCountSeqIR tail = new(remain_min, remain_max, is_greedy, pattern);
+                    span[0] = fast;
+                    span[1] = tail;
+                    return 2;
+                }
+            } else if (fast_count == 0)
+            {
+                // least count is 0
+                span[0] = new RegexCountSeqIR(0, max, is_greedy, pattern);
+                return 1;
+            } else
+            {
+                // least count is infinitive
+                span[0] = new RegexCountSeqIR(-1, -1, is_greedy, pattern);
+                return 1;
+            }
+        }
+
+        private void OptimizeDot(
                      RegexCountSetIR root,
-                            List<RegexIR> ir,
+                     Span<RegexIR> ir,
                      ref int index,
                      List<RegexIR> optimizedIR,
                      RegexInfo info
         )
         {
             int next = index + 1;
-            if (next >= ir.Count)
-            {
             optimizedIR.Clear();
+            if (next >= ir.Length)
+            {
                 optimizedIR.Add(root);
                 return;
             }
             RegexIR nextIR = ir[next];
-            if (nextIR.Command == RegexIRCommand.Match_Seq)
+            if (nextIR is RegexMatchSeqIR match_seq)
             {
                 // opt .*abc style
-                RegexFindSeqIR find = new((nextIR as RegexMatchSeqIR)!.Pattern);
+                RegexFindSeqIR find = new(match_seq.Pattern);
                 optimizedIR.Add(find);
                 info.MinLength += find.Pattern.Length;
                 return;
-            } else { }
+            } else if (nextIR is RegexCountSeqIR count_seq)
+            {
+                // opt .* (abc)* or .*(abc){2,5} style
+                string pattern = count_seq.Sequence;
+                int min = count_seq.Min;
+                int max = count_seq.Max;
+                switch ((min, max))
+                {
+                    case (0, _):
+
+                        break;
+                    default:
+                        RegexFindSeqIR find = new(pattern);
+
+                        // RegexCountSeqIR 
+
+                        break;
+                }
+            }
         }
 
-        private static void OptimizeIR(
-                            List<RegexIR> ir,
+        private void OptimizeIR(
+                     Span<RegexIR> ir,
                      ref int index,
                      List<RegexIR> optimizedIR,
                      RegexInfo info
@@ -120,6 +193,8 @@ namespace StgSharp.RegularAnalysis.Text
 
             public int TryDepth { get; set; }
 
+            public int GroupCount { get; set; }
+
         }
 
     }

StgSharpDebug/TestRegexAnalyse.cs

@@ -72,7 +72,7 @@ namespace StgSharp
             }
         }
 
-        [GeneratedRegex(@"a*.[abc]*(abcd|a(bc)c)+(?<name>abc)", RegexOptions.ExplicitCapture)]
+        [GeneratedRegex(@".*a*b", RegexOptions.ExplicitCapture)]
         internal static partial Regex GetRegex();
 
     }

future/ngra-regex-ir.md

@@ -33,43 +33,32 @@
 1. 尽可能降低源生成或者运行时执行中，对多指令上下文的依赖，尽可能保证每一个IR可以单独输出最佳的代码
 2. 减少多余的结构，使得一行指令尽可能处理多的数据
 
-### 语义改写优化
+### AST优化器
 
-1. 计数器展开
-建议在lower做
-对于形如a+b或者a{2,4}b的正则表达式，可以优化为a*(ab|b)和a{2,3}(ab|b)的写法
+1. ALT合并
+将多个ALT CASE合并到一个链表中
 
-2. 确定性计数展开
-建议在lower做
-对于形如a{m,n}的正则表达式，将其展开为a{m}a{0,n-m}的形式
+2. SPAN合并
+将连续的CHAR CONCAT合并为一个char span
 
-3. charset合并
-建议在ast-opt做
-对于形如[ abc ]|[ def ]的表达式，将其合并为[ abcdef ]
+3. alt合并
+将多个alt分支中的公共部分提取出来
 
-4. charset展开
-在lower做
-对于形如abc[ de ]的表达式，如果字符集容量不超过4，可以站卡为(abcd|abce)形式
+### IR优化器
 
-### 匹配策略改变
+1. .*a特征，优化为
+FIND_SEQ(a, last)
+.*?a特征，优化为
+FIND_SEQ(a, first)
 
-1. 长度预测
-在source-gen阶段做
-对于一个正则表达式，可以计算其所需的最小长度，可以在开始的时候提前进行比较
+2. a+特征，优化为
+MATCH_SEQ(a)
+COUNT_SEQ(a,0,+inf,greedy)
 
-2. .*优化
-在lower阶段做
-对于COUNT_SET min=0 max=-1 "."指令，也就是.*操作，将后续指令从match转为find
+3. a{1} -> a
 
-3. [ set ]*优化
-在source-gen阶段做
-对于其他的COUNT_SET min=0 max=-1 "???"指令，使用IndexOf，IndexOfAnyExcept等进行优化
+4. .\*a\*特征，优化为.*
 
-4. 首字母检查
-**这个不好做，因为IR直接把ALT打碎成if-else串了**
-对于(abc|defg|xyz)表达式，可以检查其首字母
-
-### C# span opt trick
-
-1. Span.StartWith
-2. [ 0-9 ]展开为IndexOf("0123456789")
+5. a{m,n}特征，展开为
+MATCH_SEQ(aa...m个a....aa)
+COUNT_SEQ(a,0,n,greedy)