fix(mlirlite): 局部窥孔优化每个函数体只执行一次

PrintModule 会按 STUB/TEXT/FULL 三次 dump 同一模块，而 FunctionPrint 每次都跑 _peephole_opt；T2（entry-slot store→load 转发）不是幂等变换，第二遍会误删仍有 load 指向的 entry alloca，留下悬空 SSA 名（mlir-opt: op using value defined outside the region）。给 Function 加 PeepDone 守卫，优化只作用于 builder 产出的原始文本。

mlirlite/__function.vp

@@ -90,6 +90,7 @@ novirtual class Function(GSListNode[Function]):
     AttrGroupId: int                 # attribute group id (>0 emits #N on the function line and attributes #N at module end)
     NameLen: sizet                # function name length (computed once at creation, always == strlen(Name); appended last so existing field offsets stay)
     DbgRef: str            # DISubprogram ref (kept as-is; ignored by MLIR printing, e.g. "!3")
+    PeepDone: int                    # 1=local peephole already applied to this body (runs once; see FunctionPrint)
 
 
 # ============================================================
@@ -150,8 +151,8 @@ def new_param(pool: memhub.MemBuddy*, ty: LLVMType*,
     return ptr
 
 
-# Function hardcoded size: Next(8) + Name(8) + RetTy(8) + Params(8) + Blocks(8) + IsDeclared(4) + IsVarArg(4) + Attrs(8) + AttrGroup(8) + AttrGroupId(8) + NameLen(8) + DbgRef(8) = 88 bytes (same layout as llvmlite)
-define FUNC_SIZE = 88
+# Function hardcoded size: Next(8) + Name(8) + RetTy(8) + Params(8) + Blocks(8) + IsDeclared(4) + IsVarArg(4) + Attrs(8) + AttrGroup(8) + AttrGroupId(8) + NameLen(8) + DbgRef(8) + PeepDone(8) = 96 bytes (same layout as llvmlite)
+define FUNC_SIZE = 96
 
 def new_function(pool: memhub.MemBuddy*, name: str,
                  ret_ty: LLVMType*) -> Function*:
@@ -167,6 +168,7 @@ def new_function(pool: memhub.MemBuddy*, name: str,
     ptr.Attrs = None
     ptr.AttrGroup = None
     ptr.AttrGroupId = 0
+    ptr.PeepDone = 0
     # NameLen computed once: Name never changes, so NameLen == strlen(Name) (avoids repeated strlen).
     # name=None sets 0, matching new_line's null convention (explicit for fixed semantics, not allocator behavior).
     if name is not None:
@@ -3209,8 +3211,13 @@ def FunctionPrint(buf: str, size: sizet,
     # no-op bitcast removal): peepholes match by name and delete lines by setting Buf=None.
     # They act on the builders' intermediate instruction text and are orthogonal to MLIR rendering;
     # RenumberSSA internally skips declare functions (IsDeclared==1).
-    if func.IsDeclared == 0 and G_PeepEnable != 0:
+    # Run at most ONCE per body: the module is printed several times (STUB/TEXT/FULL, see PrintModule)
+    # and the T2 forwarding is NOT idempotent — a second pass over the already-optimized text can
+    # drop an entry alloca whose use was only reachable through a line the first pass had removed,
+    # leaving dangling SSA names (mlir-opt: "op using value defined outside the region").
+    if func.IsDeclared == 0 and G_PeepEnable != 0 and func.PeepDone == 0:
         _peephole_opt(func, pool)
+        func.PeepDone = 1
     RenumberSSA(func, pool)
 
     _MlirTablesInit(pool)