[TableGen][MC] Pass a MCSubtargetInfo instance into resolveVariantSchedClassImpl (#161886)

`Target_MC::resolveVariantSchedClassImpl` is the implementation function
for `TargetGenMCSubtargetInfo::resolveVariantSchedClass`. Despite being
only called by `resolveVariantSchedClass`,
`resolveVariantSchedClassImpl` is still a standalone function that
cannot access a MCSubtargetInfo through `this` (i.e.
`TargetGenMCSubtargetInfo`). And having access to a `MCSubtargetInfo`
could be useful for some (future) SchedPredicate.

This patch modifies TableGen to generate `resolveVariantSchedClassImpl`
with an additional `MCSubtargetInfo` argument passing in. Note that this
does not change any public interface in either `TargetGenMCSubtargetInfo
` or `MCSubtargetInfo`, as `resolveVariantSchedClassImpl` is basically
an internal function.

Author: mshockwave

llvm/test/TableGen/ResolveSchedClass.td

@@ -0,0 +1,18 @@
+// RUN: llvm-tblgen -gen-subtarget -I %p/../../include %s -o - | FileCheck %s
+
+include "llvm/Target/Target.td"
+
+def TestTargetInstrInfo : InstrInfo;
+
+def TestTarget : Target {
+  let InstructionSet = TestTargetInstrInfo;
+}
+
+// CHECK:  unsigned resolveVariantSchedClassImpl(unsigned SchedClass,
+// CHECK-NEXT:      const MCInst *MI, const MCInstrInfo *MCII, const MCSubtargetInfo &STI, unsigned CPUID)
+
+// CHECK: unsigned resolveVariantSchedClass(unsigned SchedClass,
+// CHECK-NEXT:    const MCInst *MI, const MCInstrInfo *MCII,
+// CHECK-NEXT:    unsigned CPUID) const override {
+// CHECK-NEXT:   return TestTarget_MC::resolveVariantSchedClassImpl(SchedClass, MI, MCII, *this, CPUID);
+// CHECK-NEXT: }

llvm/utils/TableGen/SubtargetEmitter.cpp

@@ -1761,7 +1761,7 @@ void SubtargetEmitter::emitSchedModelHelpers(const std::string &ClassName,
      << "\n::resolveVariantSchedClass(unsigned SchedClass, const MCInst *MI,"
      << " const MCInstrInfo *MCII, unsigned CPUID) const {\n"
      << "  return " << Target << "_MC"
-     << "::resolveVariantSchedClassImpl(SchedClass, MI, MCII, CPUID);\n"
+     << "::resolveVariantSchedClassImpl(SchedClass, MI, MCII, *this, CPUID);\n"
      << "} // " << ClassName << "::resolveVariantSchedClass\n\n";
 
   STIPredicateExpander PE(Target, /*Indent=*/0);
@@ -1923,7 +1923,8 @@ void SubtargetEmitter::parseFeaturesFunction(raw_ostream &OS) {
 void SubtargetEmitter::emitGenMCSubtargetInfo(raw_ostream &OS) {
   OS << "namespace " << Target << "_MC {\n"
      << "unsigned resolveVariantSchedClassImpl(unsigned SchedClass,\n"
-     << "    const MCInst *MI, const MCInstrInfo *MCII, unsigned CPUID) {\n";
+     << "    const MCInst *MI, const MCInstrInfo *MCII, "
+     << "const MCSubtargetInfo &STI, unsigned CPUID) {\n";
   emitSchedModelHelpersImpl(OS, /* OnlyExpandMCPredicates */ true);
   OS << "}\n";
   OS << "} // end namespace " << Target << "_MC\n\n";
@@ -1945,7 +1946,7 @@ void SubtargetEmitter::emitGenMCSubtargetInfo(raw_ostream &OS) {
      << "      const MCInst *MI, const MCInstrInfo *MCII,\n"
      << "      unsigned CPUID) const override {\n"
      << "    return " << Target << "_MC"
-     << "::resolveVariantSchedClassImpl(SchedClass, MI, MCII, CPUID);\n";
+     << "::resolveVariantSchedClassImpl(SchedClass, MI, MCII, *this, CPUID);\n";
   OS << "  }\n";
   if (TGT.getHwModes().getNumModeIds() > 1) {
     OS << "  unsigned getHwModeSet() const override;\n";
@@ -2073,7 +2074,8 @@ void SubtargetEmitter::run(raw_ostream &OS) {
   OS << "class DFAPacketizer;\n";
   OS << "namespace " << Target << "_MC {\n"
      << "unsigned resolveVariantSchedClassImpl(unsigned SchedClass,"
-     << " const MCInst *MI, const MCInstrInfo *MCII, unsigned CPUID);\n"
+     << " const MCInst *MI, const MCInstrInfo *MCII, "
+     << "const MCSubtargetInfo &STI, unsigned CPUID);\n"
      << "} // end namespace " << Target << "_MC\n\n";
   OS << "struct " << ClassName << " : public TargetSubtargetInfo {\n"
      << "  explicit " << ClassName << "(const Triple &TT, StringRef CPU, "