[NewPM] Add explicit init value to -enable-new-pm

[aeubanks]

Summary

So it's easier to test with it on by default.

[ychen]

LGTM

[MaskRay]

llvm/tools/opt/opt.cpp

75

false is the default value so this appears to be NFC...

[aeubanks]

llvm/tools/opt/opt.cpp

75

I can more easily change the default value to true and test this way.
If there is a better way I'd like to know.

[MaskRay]

llvm/tools/opt/opt.cpp

75

Adding/removing cl::init(true) is very straightforward. Why is this NFC change needed?

[aeubanks]

llvm/tools/opt/opt.cpp

75

It's easier for me to replace "false" with "true" than to type the whole thing out.
Also, at some point I want to add a CMake variable which controls this flag's default value (same as the one that controls clang's NPM default behavior), and this is one step to that.

[MaskRay]

llvm/tools/opt/opt.cpp

75

If adding a cmake variable is like moving from 0 to 1, then this NFC patch seems to me 0 to 0.1

I wonder why we didn't move directly to 1. This patch added unnecessary churn to the history.

[aeubanks]

llvm/tools/opt/opt.cpp

75

Ok, maybe the CMake argument isn't so strong, but this patch still does make my life just a little easier when testing NPM with check-llvm. I'm not sure where the threshold for a patch's usefulness is for it to be worth a commit.

[hans]

llvm/tools/opt/opt.cpp

75

I don't think churning the version history is a concern here, and I don't see that the patch is doing anything weird here, just spelling out the default value and making it easier to flip with a one-liner.

If this makes Arthur's work towards enabling the new pm easier, I believe that certainly puts it above the threshold.

llvm/tools/opt/opt.cpp

 static codegen::RegisterCodeGenFlags CFG;
 
 // The OptimizationList is automatically populated with registered Passes by the
 // PassNameParser.
 //
 static cl::list<const PassInfo*, bool, PassNameParser>
 PassList(cl::desc("Optimizations available:"));
 
-static cl::opt<bool>
-    EnableNewPassManager("enable-new-pm",
-                         cl::desc("Enable the new pass manager"));
+static cl::opt<bool> EnableNewPassManager(
+    "enable-new-pm", cl::desc("Enable the new pass manager"), cl::init(false));
 
 // This flag specifies a textual description of the optimization pass pipeline
 // to run over the module. This flag switches opt to use the new pass manager
 // infrastructure, completely disabling all of the flags specific to the old
 // pass management.
 static cl::opt<std::string> PassPipeline(
     "passes",
     cl::desc("A textual description of the pass pipeline for optimizing"),