[PM] Add GVNSink to the pipeline

[davide]

Summary

Again, another oversight. With this, the two pipelines should be in sync again (modulo LoopUnswitch, but I know you're already working on that :))

[chandlerc]

Do you want to add a test to the defaults file that enables both? I don't feel strongly while they're off-by-default. LGTM either way.

lib/Passes/PassBuilder.cpp

static cl::opt<bool>
     RunNewGVN("enable-npm-newgvn", cl::init(false),
               cl::Hidden, cl::ZeroOrMore,
               cl::desc("Run NewGVN instead of GVN"));
 
 static cl::opt<bool> EnableGVNHoist(
     "enable-npm-gvn-hoist", cl::init(false), cl::Hidden,
     cl::desc("Enable the GVN hoisting pass for the new PM (default = off)"));
 
+static cl::opt<bool> EnableGVNSink(
+    "enable-npm-gvn-sink", cl::init(false), cl::Hidden,
+    cl::desc("Enable the GVN hoisting pass for the new PM (default = off)"));
+
 static Regex DefaultAliasRegex(
     "^(default|thinlto-pre-link|thinlto|lto-pre-link|lto)<(O[0123sz])>$");
 
 static bool isOptimizingForSize(PassBuilder::OptimizationLevel Level) {
   switch (Level) {
   case PassBuilder::O0:
   case PassBuilder::O1:
   case PassBuilder::O2:
PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
 
   // Catch trivial redundancies
   FPM.addPass(EarlyCSEPass());
 
   // Hoisting of scalars and load expressions.
   if (EnableGVNHoist)
     FPM.addPass(GVNHoistPass());
 
+  // Global value numbering based sinking.
+  if (EnableGVNSink) {
+    FPM.addPass(GVNSinkPass());
+    FPM.addPass(SimplifyCFGPass());
+  }
+
   // Speculative execution if the target has divergent branches; otherwise nop.
   FPM.addPass(SpeculativeExecutionPass());
 
   // Optimize based on known information about branches, and cleanup afterward.
   FPM.addPass(JumpThreadingPass());
   FPM.addPass(CorrelatedValuePropagationPass());
   FPM.addPass(SimplifyCFGPass());
   FPM.addPass(InstCombinePass());