[CFGPrinter] Allow CFG dumps with a given filename (#112906)

Add functions to print the CFG via the debugger using a specified
filename.

This is useful when comparing CFGs for the same function before vs after
a change, or when handling functions with names that are too long to be
file names.

Author: LewisCrawford

llvm/include/llvm/IR/Function.h

@@ -942,9 +942,14 @@ class LLVM_ABI Function : public GlobalObject, public ilist_node<Function> {
   ///
   void viewCFG() const;
 
+  /// viewCFG - This function is meant for use from the debugger. It works just
+  /// like viewCFG(), but generates the dot file with the given file name.
+  void viewCFG(const char *OutputFileName) const;
+
   /// Extended form to print edge weights.
   void viewCFG(bool ViewCFGOnly, const BlockFrequencyInfo *BFI,
-               const BranchProbabilityInfo *BPI) const;
+               const BranchProbabilityInfo *BPI,
+               const char *OutputFileName = nullptr) const;
 
   /// viewCFGOnly - This function is meant for use from the debugger.  It works
   /// just like viewCFG, but it does not include the contents of basic blocks
@@ -953,6 +958,10 @@ class LLVM_ABI Function : public GlobalObject, public ilist_node<Function> {
   ///
   void viewCFGOnly() const;
 
+  /// viewCFG - This function is meant for use from the debugger. It works just
+  /// like viewCFGOnly(), but generates the dot file with the given file name.
+  void viewCFGOnly(const char *OutputFileName) const;
+
   /// Extended form to print edge weights.
   void viewCFGOnly(const BlockFrequencyInfo *BFI,
                    const BranchProbabilityInfo *BPI) const;

llvm/lib/Analysis/CFGPrinter.cpp

@@ -136,12 +136,18 @@ PreservedAnalyses CFGOnlyPrinterPass::run(Function &F,
 ///
 void Function::viewCFG() const { viewCFG(false, nullptr, nullptr); }
 
+void Function::viewCFG(const char *OutputFileName) const {
+  viewCFG(false, nullptr, nullptr, OutputFileName);
+}
+
 void Function::viewCFG(bool ViewCFGOnly, const BlockFrequencyInfo *BFI,
-                       const BranchProbabilityInfo *BPI) const {
+                       const BranchProbabilityInfo *BPI,
+                       const char *OutputFileName) const {
   if (!CFGFuncName.empty() && !getName().contains(CFGFuncName))
     return;
   DOTFuncInfo CFGInfo(this, BFI, BPI, BFI ? getMaxFreq(*this, BFI) : 0);
-  ViewGraph(&CFGInfo, "cfg" + getName(), ViewCFGOnly);
+  ViewGraph(&CFGInfo, OutputFileName ? OutputFileName : "cfg" + getName(),
+            ViewCFGOnly);
 }
 
 /// viewCFGOnly - This function is meant for use from the debugger.  It works
@@ -151,6 +157,10 @@ void Function::viewCFG(bool ViewCFGOnly, const BlockFrequencyInfo *BFI,
 ///
 void Function::viewCFGOnly() const { viewCFGOnly(nullptr, nullptr); }
 
+void Function::viewCFGOnly(const char *OutputFileName) const {
+  viewCFG(true, nullptr, nullptr, OutputFileName);
+}
+
 void Function::viewCFGOnly(const BlockFrequencyInfo *BFI,
                            const BranchProbabilityInfo *BPI) const {
   viewCFG(true, BFI, BPI);