[gicombiner] Allow generated CombinerHelpers to have additional arguments

[dsanders]

Summary

This allows combiners to delegate to other helpers or depend
on additional information. It's not great as an overall
solution though as callers must provide the argument on every call, even for
static data like an additional helper. Another patch will follow to
support additional members of the generated combiner.

[aditya_nandakumar]

Doesn't https://reviews.llvm.org/D81863 make this unnecessary?

[dsanders]

In D81862#2094055, @aditya_nandakumar wrote:

Doesn't https://reviews.llvm.org/D81863 make this unnecessary?

No, at the moment some targets are still using this for their CombinerHelper. Even if we make CombinerHelper a standard one there's still potential for this to be used by non-static things like the results of compute known bits* or some other (possibly target specific) localized knowledge. Essentially, D81863 covers static/global knowledge and this covers dynamic/local knowledge.

*The analysis pass itself would be static and but the results are dynamic so it really comes down to the preferred way to use that one.

llvm/include/llvm/Target/GlobalISel/Combine.td

class GICombineGroup<list<GICombine> rules> : GICombine {
   // The rules contained in this group. The rules in a group are flattened into
   // a single list and sorted into whatever order is most efficient. However,
   // they will never be re-ordered such that behaviour differs from the
   // specified order. It is therefore possible to use the order of rules in this
   // list to describe priorities.
   let Rules = rules;
 }
 
+class GICombinerHelperArg<string type, string name> {
+  string Type = type;
+  string Name = name;
+}
+
 // Declares a combiner helper class
 class GICombinerHelper<string classname, list<GICombine> rules>
     : GICombineGroup<rules> {
   // The class name to use in the generated output.
   string Classname = classname;
   // The name of a run-time compiler option that will be generated to disable
   // specific rules within this combiner.
   string DisableRuleOption = ?;
+  // Any additional arguments that should be appended to the tryCombine*().
+  list<GICombinerHelperArg> AdditionalArguments =
+      [GICombinerHelperArg<"CombinerHelper &", "Helper">];
 }
 class GICombineRule<dag defs, dag match, dag apply> : GICombine {
   /// Defines the external interface of the match rule. This includes:
   /// * The names of the root nodes (requires at least one)
   /// See GIDefKind for details.
   dag Defs = defs;
 
   /// Defines the things which must be true for the pattern to match

llvm/utils/TableGen/GICombinerEmitter.cpp

if (Leaf.isFullyTested() &&
          << "llvm_unreachable(\"Combine rule elision was incorrect\");\n"
          << Indent << "return false;\n";
     }
   }
   if (!AnyFullyTested)
     OS << Indent << "return false;\n";
 }
 
+static void emitAdditionalHelperMethodArguments(raw_ostream &OS,
+                                                Record *Combiner) {
+  for (Record *Arg : Combiner->getValueAsListOfDefs("AdditionalArguments"))
+    OS << ",\n    " << Arg->getValueAsString("Type")
+       << Arg->getValueAsString("Name");
+}
+
 void GICombinerEmitter::run(raw_ostream &OS) {
   gatherRules(Rules, Combiner->getValueAsListOfDefs("Rules"));
   if (StopAfterParse) {
     MatchDagCtx.print(errs());
     PrintNote(Combiner->getLoc(),
               "Terminating due to -gicombiner-stop-after-parse");
     return;
   }
OS << "#ifdef " << Name.upper() << "_GENCOMBINERHELPER_H\n"
      << "public:\n"
      << "  bool parseCommandLineOption();\n"
      << "  bool isRuleDisabled(unsigned ID) const;\n"
      << "  bool setRuleDisabled(StringRef RuleIdentifier);\n"
      << "\n"
      << "  bool tryCombineAll(\n"
      << "    GISelChangeObserver &Observer,\n"
      << "    MachineInstr &MI,\n"
-     << "    MachineIRBuilder &B,\n"
-     << "    CombinerHelper &Helper) const;\n"
-     << "};\n\n";
+     << "    MachineIRBuilder &B";
+  emitAdditionalHelperMethodArguments(OS, Combiner);
+  OS << ") const;\n";
+  OS << "};\n\n";
 
   emitNameMatcher(OS);
 
   OS << "bool " << getClassName()
      << "::setRuleDisabled(StringRef RuleIdentifier) {\n"
      << "  std::pair<StringRef, StringRef> RangePair = "
         "RuleIdentifier.split('-');\n"
      << "  if (!RangePair.second.empty()) {\n"
OS << "#ifdef " << Name.upper() << "_GENCOMBINERHELPER_CPP\n"
      << "    if (!setRuleDisabled(Identifier))\n"
      << "      return false;\n"
      << "  return true;\n"
      << "}\n\n";
 
   OS << "bool " << getClassName() << "::tryCombineAll(\n"
      << "    GISelChangeObserver &Observer,\n"
      << "    MachineInstr &MI,\n"
-     << "    MachineIRBuilder &B,\n"
-     << "    CombinerHelper &Helper) const {\n"
+     << "    MachineIRBuilder &B";
+  emitAdditionalHelperMethodArguments(OS, Combiner);
+  OS << ") const {\n"
      << "  MachineBasicBlock *MBB = MI.getParent();\n"
      << "  MachineFunction *MF = MBB->getParent();\n"
      << "  MachineRegisterInfo &MRI = MF->getRegInfo();\n"
      << "  SmallVector<MachineInstr *, 8> MIs = { &MI };\n\n"
      << "  (void)MBB; (void)MF; (void)MRI;\n\n";
 
   OS << "  // Match data\n";
   for (const auto &Rule : Rules)