[BOLT] Add dump-dot-func option for selective function CFG dumping (#153007)

## Change:
* Added `--dump-dot-func` command-line option that allows users to dump
CFGs only for specific functions instead of dumping all functions (the
current only available option being `--dump-dot-all`)

## Usage:
* Users can now specify function names or regex patterns (e.g.,
`--dump-dot-func=main,helper` or `--dump-dot-func="init.*`") to generate
.dot files only for functions of interest
* Aims to save time when analysing specific functions in large binaries
(e.g., only dumping graphs for performance-critical functions identified
through profiling) and we can now avoid reduce output clutter from
generating thousands of unnecessary .dot files when analysing large
binaries

## Testing
The introduced test `dump-dot-func.test` confirms the new option does
the following:

- [x] 1. `dump-dot-func` can correctly filter a specified functions
- [x] 2. Can achieve the above with regexes
- [x] 3. Can do 1. with a list of functions
- [x] No option specified creates no dot files
- [x] Passing in a non-existent function generates no dumping messages
- [x] `dump-dot-all` continues to work as expected

1 files changed, 2 insertions, 1 deletions

diff --git a/bolt/lib/Rewrite/BinaryPassManager.cpp b/bolt/lib/Rewrite/BinaryPassManager.cpp
index 996d2e9..0ddb73f 100644
--- a/bolt/lib/Rewrite/BinaryPassManager.cpp
+++ b/bolt/lib/Rewrite/BinaryPassManager.cpp
@@ -52,6 +52,7 @@ namespace opts {
 extern cl::opt<bool> PrintAll;
 extern cl::opt<bool> PrintDynoStats;
 extern cl::opt<bool> DumpDotAll;
+extern bool shouldDumpDot(const bolt::BinaryFunction &Function);
 extern cl::opt<std::string> AsmDump;
 extern cl::opt<bolt::PLTCall::OptType> PLT;
 extern cl::opt<bolt::IdenticalCodeFolding::ICFLevel, false,
@@ -340,7 +341,7 @@ Error BinaryFunctionPassManager::runPasses() {
 
       Function.print(BC.outs(), Message);
 
-      if (opts::DumpDotAll)
+      if (opts::shouldDumpDot(Function))
         Function.dumpGraphForPass(PassIdName);
     }
   }