[llvm-extract] Add option for recursive extraction

[loladiro]

Summary

Particularly, with --delete, this can be very useful for testing
new optimizations on some hotspots, without having to run it on the whole
application. E.g. as such:

llvm-extract app.bc --recursive --rfunc .*hotspot.* > hotspot.bc
llvm-extract app.bc --recursive --delete --rfunc .*hotspot.* > residual.bc
llc -filetype=obj residual.bc > residual.o
# Play with hotspot.bc here
llc -filetype=obj hotspot.bc > hotspot.o
cc -o app residual.o hotspot.o

[davide]

Please add a basic test and a test with mutually recursive calls. The basic logic seems fine to me, some nits (sorry for being pedantic).

tools/llvm-extract/llvm-extract.cpp

236

explicit type when non-obvious.

244

Can we have a slightly better diagnostic here? Something like Cannot materialize function F + F->getName().

245

I generally prefer early continue to avoid many levels of nesting (there are a few in this case), so I'd rewrite the loop as:

for (...) {
  auto *CI = dyn_cast<>();
  if (!CI)
    continue;
  [...]
}

but I don't feel strong about it, so, up to you.

247

and probably auto when the type is obvious`.

[davide]

tools/llvm-extract/llvm-extract.cpp

21–23

Also this reordering seems unrelated? I think it's a good cleanup but can be committed separately (without pre-commit code review).

[loladiro]

Address review comments

[loladiro]

tools/llvm-extract/llvm-extract.cpp

21–23

I run git clang-format as a commit hook and it reorders the include list. Happy to commit separately, but I though the general policy on that was just to put formatting changes into the commit where you're editing the code.

244

IIRC, ExitOnError will add diagnostics if the Error object provides them.

[davide]

LGTM

tools/llvm-extract/llvm-extract.cpp

 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Bitcode/BitcodeWriterPass.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/IRPrintingPasses.h"
+#include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IRReader/IRReader.h"
-#include "llvm/IR/LegacyPassManager.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/PrettyStackTrace.h"
 #include "llvm/Support/Regex.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/SourceMgr.h"
OutputFilename("o", cl::desc("Specify output filename"),
                cl::value_desc("filename"), cl::init("-"));
 
 static cl::opt<bool>
 Force("f", cl::desc("Enable binary output on terminals"));
 
 static cl::opt<bool>
 DeleteFn("delete", cl::desc("Delete specified Globals from Module"));
 
+static cl::opt<bool>
+    Recursive("recursive",
+              cl::desc("Recursively extract all called functions"));
+
 // ExtractFuncs - The functions to extract from the module.
 static cl::list<std::string>
 ExtractFuncs("func", cl::desc("Specify function to extract"),
              cl::ZeroOrMore, cl::value_desc("function"));
 
 // ExtractRegExpFuncs - The functions, matched via regular expression, to
 // extract from the module.
 static cl::list<std::string>
if (!match) {
              << ExtractRegExpFuncs[i] << "'!\n";
       return 1;
     }
   }
 
   // Use *argv instead of argv[0] to work around a wrong GCC warning.
   ExitOnError ExitOnErr(std::string(*argv) + ": error reading input: ");
 
+  if (Recursive) {
+    std::vector<llvm::Function *> Workqueue;
+    for (auto *GV : GVs) {
+      if (Function *F = dyn_cast<Function>(GV)) {
+        Workqueue.push_back(F);
+      }
+    }
+    while (!Workqueue.empty()) {
+      Function *F = &*Workqueue.back();
+      Workqueue.pop_back();
+      ExitOnErr(F->materialize());
+      for (auto &BB : *F) {
+        for (auto &I : BB) {
+          if (CallInst *CI = dyn_cast<CallInst>(&I)) {
+            if (Function *CF = CI->getCalledFunction()) {
+              if (!CF->isDeclaration() && !GVs.count(CF)) {
+                GVs.insert(CF);
+                Workqueue.push_back(CF);
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+
   auto Materialize = [&](GlobalValue &GV) { ExitOnErr(GV.materialize()); };
 
   // Materialize requisite global values.
   if (!DeleteFn) {
     for (size_t i = 0, e = GVs.size(); i != e; ++i)
       Materialize(*GVs[i]);
   } else {
     // Deleting. Materialize every GV that's *not* in GVs.