Magic源码阅读（四）——DRC检查的实现（上）

当我们从版图文件中读取数据并生成我们基于角勾链的数据模式后，下一步就是在我们的版图上进行DRC（设计规则检查），接下来让我们看一下magic是如何进行常用的DRC的。

DRC部分涉及的源码主要有以下几个源文件

drc.h            #declaration of the main interface, defination of global variablesDRCarray.c        #implementation of array related design rule checkDRCbasic.c        #implementation of basic design rule check method#including interatcion, overlap, distance, etc...DRCcif.c      #maybe related to the cif format layout fileDRCcontin.c     #implementation of continuously design rule check methodDRCextend.c     #implementation of extend design rule check method#including angle, length, width, rect size, etc...DRCmain.c       #implementation of main interface and commandDRCprint.c     #some additional function related printingDRCsubcell.c  #implementation of subcell design rule check method#including interaction, overlap, flat, etc...DRCtech.c       #Technology initialization for the DRC module

先从DRCmain.c看起。

首先是一系列全局变量的定义，这些全局变量用来存储DRC发现的错误数据，magic将DRC检查DRCBasicCheck与错误的打印drcPrintError和绘制drcPrintError解耦为不同的方法，用全局变量来传递数据。

DRCKeep *DRCStyleList = NULL;DRCStyle *DRCCurStyle = NULL;/* Used by both routines: */int DRCErrorCount;       /* Incremented by each call to either routine.*//* Used by drcPaintError: */CellDef *DRCErrorDef;       /* Place to paint error tiles. */
TileType DRCErrorType;      /* Type of error tile to paint. *//* Used by drcPrintError: */int *DRCErrorList;        /* List of DRC error type counts */
HashTable DRCErrorTable;    /* Table of DRC errors and geometry *//* Global variables used by all DRC modules to record statistics.* For each statistic we keep two values, the count since stats* were last printed (in DRCstatXXX), and the total count (in* drcTotalXXX).*/int DRCstatSquares = 0;      /* Number of DRCStepSize-by-DRCStepSize* squares processed by continuous checker.*/
int DRCstatTiles = 0;      /* Number of tiles processed by basic* checker.*/
int DRCstatEdges = 0;      /* Number of "atomic" edges processed* by basic checker.*/
int DRCstatRules = 0;      /* Number of rules processed by basic checker* (rule = one constraint for one edge).*/
int DRCstatSlow = 0;       /* Number of places where constraint doesn't* all fall in a single tile.*/
int DRCstatInteractions = 0;   /* Number of times drcInt is called to check* an interaction area.*/
int DRCstatIntTiles = 0;   /* Number of tiles processed as part of* subcell interaction checks.*/
int DRCstatCifTiles = 0;   /* Number of tiles processed as part of* cif checks.*/
int DRCstatArrayTiles = 0; /* Number of tiles processed as part of* array interaction checks.*/

接下来的drcPrintError和drcPrintError就不多说了，分别是对应的错误打印和窗口UI的更新的实现，我们继续往下看：

/** 找出某个给定区域内的所有错误并打印所有不同类型的违背的规则*/void
DRCWhy(dolist, use, area) bool dolist;          /** Generate Tcl list for value*/CellUse *use;          /* Use in whose definition to start* the hierarchical check.*/Rect *area;               /* Area, in def's coordinates, that* is to be checked.*/
{SearchContext scx;Rect box;int i;extern int drcWhyFunc();      /* Forward reference. *//* Create a hash table to eliminate duplicate messages. */DRCErrorList = (int *)mallocMagic((DRCCurStyle->DRCWhySize + 1) * sizeof(int));for (i = 0; i <= DRCCurStyle->DRCWhySize; i++)DRCErrorList[i] = 0;DRCErrorCount = 0;box = DRCdef->cd_bbox;/* Undo will only slow things down in here, so turn it off. */UndoDisable();scx.scx_use = use;scx.scx_x = use->cu_xlo;scx.scx_y = use->cu_ylo;scx.scx_area = *area;scx.scx_trans = GeoIdentityTransform;drcWhyFunc(&scx, (pointertype)dolist);UndoEnable();/* Delete the error list */freeMagic(DRCErrorList);/* Redisplay the DRC yank definition in case anyone is looking* at it.*/DBReComputeBbox(DRCdef);(void) GeoInclude(&DRCdef->cd_bbox, &box);/** 根据找到的错误发更新window*/DBWAreaChanged(DRCdef, &box, DBW_ALLWINDOWS, &DBAllButSpaceBits); if (DRCErrorCount == 0) TxPrintf("No errors found.\n");
}/** 由drcWhy调用，drcWhy将参数封装为searchcontent传递给drcWhyFunc*//* ARGSUSED */
int
drcWhyFunc(scx, cdarg)SearchContext *scx;       /* Describes current state of search. */ClientData cdarg;       /* Used to hold boolean value "dolist" */
{CellDef *def = scx->scx_use->cu_def;bool dolist = (bool)((pointertype)cdarg);/* Check paint and interactions in this subcell. *//* * 最终调用的两个函数是DRCInteractionCheck和DRCArrayCheck*/(void) DRCInteractionCheck(def, &scx->scx_area, &scx->scx_area,(dolist) ? drcListError : drcPrintError,(ClientData) scx);(void) DRCArrayCheck(def, &scx->scx_area,(dolist) ? drcListError : drcPrintError,(ClientData) scx);/* New behavior:  Don't search children, instead propagate errors up. *//* (void) DBCellSrArea(scx, drcWhyFunc, (ClientData)cdarg); */return 0;
}

可见当我们使用drc why命令检查某个区域时，drc命令将传入的参数包装为searchContent搜索上下文，传递给drcWhyFunc，由其完成DRC(内部调用的DRCInteractionCheck和DRCArrayCheck两个函数)，然后通过调用dbwind下的相关函数进行错误的打印和窗口的更新。

而接下来的DRCcheck则有所不同：

void
DRCCheck(use, area)CellUse *use;        /* Top-level use of hierarchy. */Rect *area;            /* This area is rechecked everywhere in the* hierarchy underneath use.*/
{SearchContext scx;extern int drcCheckFunc();   /* Forward reference. *//** DRC Check先进行了读取，将要检查的区域加载进内存*/DBCellReadArea(use, area);/** 同样封装了参数，传递并调用了函数DRCCheckFunc*/scx.scx_use = use;scx.scx_x = use->cu_xlo;scx.scx_y = use->cu_ylo;scx.scx_area = *area;scx.scx_trans = GeoIdentityTransform;(void) drcCheckFunc(&scx, (ClientData) NULL);
}/* ARGSUSED */
int
drcCheckFunc(scx, cdarg)SearchContext *scx;ClientData cdarg;        /* Not used. */
{Rect cellArea;CellDef *def;/* * 将区域裁剪为单元格的大小，然后重新检查该区域。 通过直接绘制检查信息，然后调用DRCCheckThis，仅将单元格添加到要检查的单元格列表中，即可处理重新检查。 这避免了通常由DRCCheckThis进行的向上的分层搜索，但是我们不希望这样（速度很慢）。*/cellArea = scx->scx_area;def = scx->scx_use->cu_def;GeoClip(&cellArea, &def->cd_bbox);GEO_EXPAND(&cellArea, DRCTechHalo, &cellArea);DBPaintPlane(def->cd_planes[PL_DRC_CHECK], &cellArea,DBStdPaintTbl(TT_CHECKPAINT, PL_DRC_CHECK),(PaintUndoInfo *) NULL);DRCCheckThis(def, TT_CHECKPAINT, (Rect *) NULL);/* New behavior:  Don't search children, instead propagate errors up. *//* (void) DBCellSrArea(scx, drcCheckFunc, (ClientData) NULL); *//* As a special performance hack, if the complete cell area is* handled here, don't bother to look at any more array elements.*/if (GEO_SURROUND(&cellArea, &def->cd_bbox))return 2;else return 0;
}

可以看到check和why的区别，check在检查前需要进行读取，并且检查调用的是DRCCheckThis函数，而why底层调用的是DRCInteractionCheck和DRCArrayCheck两个函数。为什么会有这种区别呢？

DRCCheckThis在源文件DRCcontin.c中，我们带着疑问看一下DRCCheckThis的实现：

void
DRCCheckThis (celldef, operation, area)CellDef * celldef;           /* Allows check areas to propagate* up from EditCell.*/TileType  operation;     /* TT_CHECKPAINT or TT_CHECKSUBCELL */Rect    * area;           /* Area that changed. */
{CellUse         * cu;      /* Ptr to uses of the given CellDef */Rect         transRect;   /* Area in coords of parent CellDefs,* expanded if the use is in an array*/Rect               dummyRect, dummyRect2;DRCPendingCookie * p, ** pback; /* Used to insert new element in list*  of CellDefs waiting for DRC*//* Ignore read-only, internal, and vendor GDS cells.  None of these    *//* can contain DRC errors that could be fixed in magic.       */if (celldef->cd_flags & (CDVENDORGDS | CDNOEDIT | CDINTERNAL)) return;/* Insert celldef into list of Defs waiting to be checked, unless    *//* it is already there.                       */pback = &DRCPendingRoot;p = DRCPendingRoot;while (p != (DRCPendingCookie *) NULL){if (p->dpc_def == celldef){*pback = p->dpc_next;break;}pback = &(p->dpc_next);p = p->dpc_next;}if (p == (DRCPendingCookie *) NULL){p = (DRCPendingCookie *) mallocMagic(sizeof (DRCPendingCookie));p->dpc_def = celldef;}p->dpc_next = DRCPendingRoot;DRCPendingRoot = p;/* Mark the area in this celldef (but don't worry about this stuff* for undo purposes).  Also, it's important to disable interrupts* in here, or the paint operation could get aborted underneath us.** Mark an area of a CellDef so that it will be checked by continuous* DRC.  Add the CellDef to the list of Defs to be checked.  If the* pointer to the area rectangle is NULL, just add the CellDef to the* list.*/if (area != (Rect *) NULL){GEO_EXPAND(area, DRCTechHalo, &dummyRect);SigDisableInterrupts();DBPaintPlane(celldef->cd_planes[PL_DRC_CHECK], &dummyRect,DBStdPaintTbl(TT_CHECKPAINT, PL_DRC_CHECK),(PaintUndoInfo *) NULL);SigEnableInterrupts();}else return;/*  Call recursively for each use of this*  CellDef in a parent.*/for (cu = celldef->cd_parents; cu != (CellUse *) NULL; cu = cu->cu_nextuse){if (cu->cu_parent == (CellDef *) NULL)      /* use for a Window */continue;/* area in coordinates of the parent Def */GeoTransRect (&(cu->cu_transform), area, &transRect);if ((cu->cu_xlo != cu->cu_xhi) || (cu->cu_ylo != cu->cu_yhi)){/* transRect needs to include all images* of "area" in the array, in coordinates* of the parent Def*/DBComputeArrayArea(area, cu, cu->cu_xhi, cu->cu_yhi, &dummyRect);GeoTransRect(&cu->cu_transform, &dummyRect, &dummyRect2);(void) GeoInclude (&dummyRect2, &transRect);}DRCCheckThis (cu->cu_parent, TT_CHECKSUBCELL, &transRect);}
}

可以看到，DRCcheckthis的实现是将当前的区域添加到待DRC的list中，由后台持续运行的DRC检查器来进行检查，同时，递归的调用以检查嵌套的cell。

个人的理解是DRCcheckthis执行的是一种粗粒度的检查，由一个持续运行的规则检查器来完成，针对的是整个版图或者版图的某一层这种大规模的数据，因此在检查前需要进行数据的加载和预处理，得到的结果是大规模的区域及其中违反规则的部分。而DRCwhy执行的是更为细粒度的检查，顾名思义会得到此处违反的具体规则是什么，检查的对象是初步检查过的图，数据已在内存中，无需加载。

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