[BOLT] Instrumentation: Add support for MacOS counters

[Elvina]

Summary

This patch adds support for generation of getter counters for AArch64 MacOS

continuation of work https://reviews.llvm.org/D151899

Elvina Yakubova,
Advanced Software Technology Lab, Huawei

[rafauler]

bolt/include/bolt/Core/MCPlusBuilder.h

1980–1985 ↗

(On Diff #527463)

Let's avoid publishing this to the target-independent interface. Make it a local helper in AArch64MCPlusBuilder

bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp

1351

nit: TempReg -> ReturnValReg

1355

assert on size being 2

[Elvina]

Updated diff based on comments - createGetter is local now

[rafauler]

LGTM

[yota9]

LGTM

bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp

InstructionListType createInstrumentedIndCallHandlerExitBB() const override {
     return Insts;
   }
 
   InstructionListType
   createInstrumentedIndTailCallHandlerExitBB() const override {
     return createInstrumentedIndCallHandlerExitBB();
   }
 
+  InstructionListType createGetter(MCContext *Ctx, const char *name) const {
+    InstructionListType Insts(4);
+    MCSymbol *Locs = Ctx->getOrCreateSymbol(name);
+    InstructionListType Addr = materializeAddress(Locs, Ctx, AArch64::X0);
+    std::copy(Addr.begin(), Addr.end(), Insts.begin());
+    assert(Addr.size() == 2 && "Invalid Addr size");
+    loadReg(Insts[2], AArch64::X0, AArch64::X0);
+    createReturn(Insts[3]);
+    return Insts;
+  }
+
+  InstructionListType createNumCountersGetter(MCContext *Ctx) const override {
+    return createGetter(Ctx, "__bolt_num_counters");
+  }
+
+  InstructionListType
+  createInstrLocationsGetter(MCContext *Ctx) const override {
+    return createGetter(Ctx, "__bolt_instr_locations");
+  }
+
+  InstructionListType createInstrTablesGetter(MCContext *Ctx) const override {
+    return createGetter(Ctx, "__bolt_instr_tables");
+  }
+
+  InstructionListType createInstrNumFuncsGetter(MCContext *Ctx) const override {
+    return createGetter(Ctx, "__bolt_instr_num_funcs");
+  }
+
   void convertIndirectCallToLoad(MCInst &Inst, MCPhysReg Reg) override {
     bool IsTailCall = isTailCall(Inst);
     if (IsTailCall)
       removeAnnotation(Inst, MCPlus::MCAnnotation::kTailCall);
     if (Inst.getOpcode() == AArch64::BL || Inst.getOpcode() == AArch64::BLR ||
         Inst.getOpcode() == AArch64::BR || Inst.getOpcode() == AArch64::B) {
 
       Inst.setOpcode(AArch64::ORRXrs);