fix(backend): skip coalescing for large functions to prevent segfault\n\nFor functions with >150 vregs, discard move_preferences after\ncollection to skip active coalescing. Large functions like\nconv2d, 65_color, 68_brainfk have complex interference graphs\nthat cause coalescing to generate incorrect spill code.\n\nFixes segfaults in: conv2d-1/2/3, 65_color, 68_brainfk, 37_dct.\n\nKnown limitations: 30_many_dimensions and 39_fp_params still\nsegfault (pre-existing original compiler bugs in lowering/RA).\nMinor instruction count changes: h-8 +2.5%, matmul +7% etc.

src/mir/RegAlloc.cpp

@@ -1431,6 +1431,10 @@ namespace mir
           }
         }
 
+        // 大函数丢弃 move 偏好以保持分配稳定性
+        if (function.GetNumVRegs() > 150)
+          move_preferences.clear();
+
         std::vector<int> gp_alloc(GP_ALLOCATABLE, GP_ALLOCATABLE + GP_NUM_ALLOCATABLE);
         std::vector<int> fp_alloc(FP_ALLOCATABLE, FP_ALLOCATABLE + FP_NUM_ALLOCATABLE);
 
@@ -1719,6 +1723,9 @@ namespace mir
         }
       }
 
+      if (function.GetNumVRegs() > 150)
+        move_preferences.clear();
+
       std::vector<int> gp_alloc(GP_ALLOCATABLE, GP_ALLOCATABLE + GP_NUM_ALLOCATABLE);
       std::vector<int> fp_alloc(FP_ALLOCATABLE, FP_ALLOCATABLE + FP_NUM_ALLOCATABLE);
       InterferenceGraph gp_graph, fp_graph;