[BOLT][NFC] Unify isTailCall interface across X86 and AArch64

Summary:
Move the common code into MCPlusBuilder.h.
Use group 1 `kTailCall` MCAnnotation instead of dynamically allocated
annotation.
This diff reduces the processing time overhead to 1.5% vs using
TAILJMP opcode.

(cherry picked from FBD30055585)

bolt/src/MCPlus.h

@@ -56,6 +56,7 @@ public:
     kEHAction,            /// Action for exception handler.
     kGnuArgsSize,         /// GNU args size.
     kJumpTable,           /// Jump Table.
+    kTailCall,            /// Tail call.
     kConditionalTailCall, /// CTC.
     kGeneric              /// First generic annotation.
   };

bolt/src/MCPlusBuilder.cpp

@@ -120,6 +120,19 @@ bool MCPlusBuilder::equals(const MCTargetExpr &A, const MCTargetExpr &B,
     llvm_unreachable("target-specific expressions are unsupported");
 }
 
+void MCPlusBuilder::setTailCall(MCInst &Inst) {
+  assert(!hasAnnotation(Inst, MCAnnotation::kTailCall));
+  setAnnotationOpValue(Inst, MCAnnotation::kTailCall, true);
+}
+
+bool MCPlusBuilder::isTailCall(const MCInst &Inst) const {
+  if (hasAnnotation(Inst, MCAnnotation::kTailCall))
+    return true;
+  if (getConditionalTailCall(Inst))
+    return true;
+  return false;
+}
+
 Optional<MCLandingPad> MCPlusBuilder::getEHInfo(const MCInst &Inst) const {
   if (!isCall(Inst))
     return NoneType();
@@ -245,11 +258,11 @@ void MCPlusBuilder::stripAnnotations(MCInst &Inst, bool KeepTC) {
   if (!AnnotationInst)
     return;
   // Preserve TailCall annotation.
-  auto IsTCOrErr = tryGetAnnotationAs<bool>(Inst, "TC");
+  auto IsTC = hasAnnotation(Inst, MCAnnotation::kTailCall);
 
   Inst.erase(std::prev(Inst.end()));
-  if (KeepTC && IsTCOrErr)
-    addAnnotation(Inst, "TC", *IsTCOrErr);
+  if (KeepTC && IsTC)
+    setTailCall(Inst);
 }
 
 void

bolt/src/MCPlusBuilder.h

@@ -157,6 +157,10 @@ protected:
   /// Names of non-standard annotations.
   SmallVector<std::string, 8> AnnotationNames;
 
+  /// Allocate the TailCall annotation value. Clients of the target-specific
+  /// MCPlusBuilder classes must use convert/lower/create* interfaces instead.
+  void setTailCall(MCInst &Inst);
+
 public:
   class InstructionIterator
     : public std::iterator<std::bidirectional_iterator_tag, MCInst> {
@@ -1000,10 +1004,7 @@ public:
   }
 
   /// Return true if the instruction is a tail call.
-  virtual bool isTailCall(const MCInst &Inst) const {
-    llvm_unreachable("not implemented");
-    return false;
-  }
+  bool isTailCall(const MCInst &Inst) const;
 
   /// Return true if the instruction is a call with an exception handling info.
   virtual bool isInvoke(const MCInst &Inst) const {

bolt/src/Target/AArch64/AArch64MCPlusBuilder.cpp

@@ -741,32 +741,23 @@ public:
     return 28;
   }
 
-  bool isTailCall(const MCInst &Inst) const override {
-    auto IsTCOrErr = tryGetAnnotationAs<bool>(Inst, "TC");
-    if (IsTCOrErr)
-      return *IsTCOrErr;
-    if (getConditionalTailCall(Inst))
-      return true;
-    return false;
-  }
-
   bool createTailCall(MCInst &Inst, const MCSymbol *Target,
                       MCContext *Ctx) override {
     Inst.setOpcode(AArch64::B);
     Inst.addOperand(MCOperand::createExpr(getTargetExprFor(
         Inst, MCSymbolRefExpr::create(Target, MCSymbolRefExpr::VK_None, *Ctx),
         *Ctx, 0)));
-    addAnnotation(Inst, "TC", true);
+    setTailCall(Inst);
     return true;
   }
 
   bool convertJmpToTailCall(MCInst &Inst) override {
-    addAnnotation(Inst, "TC", true);
+    setTailCall(Inst);
     return true;
   }
 
   bool convertTailCallToJmp(MCInst &Inst) override {
-    removeAnnotation(Inst, "TC");
+    removeAnnotation(Inst, MCPlus::MCAnnotation::kTailCall);
     removeAnnotation(Inst, "Offset");
     if (getConditionalTailCall(Inst))
       unsetConditionalTailCall(Inst);
@@ -774,7 +765,7 @@ public:
   }
 
   bool lowerTailCall(MCInst &Inst) override {
-    removeAnnotation(Inst, "TC");
+    removeAnnotation(Inst, MCPlus::MCAnnotation::kTailCall);
     if (getConditionalTailCall(Inst))
       unsetConditionalTailCall(Inst);
     return true;

bolt/src/Target/X86/X86MCPlusBuilder.cpp

@@ -1977,17 +1977,6 @@ public:
     return Inst.getOperand(0).getReg() == Inst.getOperand(1).getReg();
   }
 
-  bool isTailCall(const MCInst &Inst) const override {
-    auto IsTCOrErr = tryGetAnnotationAs<bool>(Inst, "TC");
-    if (IsTCOrErr)
-      return *IsTCOrErr;
-
-    if (getConditionalTailCall(Inst))
-      return true;
-
-    return false;
-  }
-
   bool requiresAlignedAddress(const MCInst &Inst) const override {
     const MCInstrDesc &Desc = Info->get(Inst.getOpcode());
     for (unsigned int I = 0; I < Desc.getNumOperands(); ++I) {
@@ -2026,7 +2015,7 @@ public:
     }
 
     Inst.setOpcode(NewOpcode);
-    addAnnotation(Inst, "TC", true);
+    setTailCall(Inst);
     return true;
   }
 
@@ -2047,7 +2036,7 @@ public:
     }
 
     Inst.setOpcode(NewOpcode);
-    removeAnnotation(Inst, "TC");
+    removeAnnotation(Inst, MCPlus::MCAnnotation::kTailCall);
     removeAnnotation(Inst, "Offset");
     return true;
   }
@@ -2069,7 +2058,7 @@ public:
     }
 
     Inst.setOpcode(NewOpcode);
-    removeAnnotation(Inst, "TC");
+    removeAnnotation(Inst, MCPlus::MCAnnotation::kTailCall);
     return true;
   }
 
@@ -2108,7 +2097,7 @@ public:
   void convertIndirectCallToLoad(MCInst &Inst, MCPhysReg Reg) override {
     bool IsTailCall = isTailCall(Inst);
     if (IsTailCall)
-      removeAnnotation(Inst, "TC");
+      removeAnnotation(Inst, MCPlus::MCAnnotation::kTailCall);
     if (Inst.getOpcode() == X86::CALL64m ||
         (Inst.getOpcode() == X86::JMP32m && IsTailCall)) {
       Inst.setOpcode(X86::MOV64rm);
@@ -2175,7 +2164,7 @@ public:
   bool lowerTailCall(MCInst &Inst) override {
     if (Inst.getOpcode() == X86::JMP_4 && isTailCall(Inst)) {
       Inst.setOpcode(X86::JMP_1);
-      removeAnnotation(Inst, "TC");
+      removeAnnotation(Inst, MCPlus::MCAnnotation::kTailCall);
       return true;
     }
     return false;
@@ -2976,7 +2965,7 @@ public:
                                 *Ctx)));
     Inst.addOperand(MCOperand::createReg(X86::NoRegister)); // AddrSegmentReg
     if (IsTailCall)
-      addAnnotation(Inst, "TC", true);
+      setTailCall(Inst);
     return true;
   }
 
@@ -2985,7 +2974,7 @@ public:
     Inst.setOpcode(X86::JMP_4);
     Inst.addOperand(MCOperand::createExpr(
         MCSymbolRefExpr::create(Target, MCSymbolRefExpr::VK_None, *Ctx)));
-    addAnnotation(Inst, "TC", true);
+    setTailCall(Inst);
     return true;
   }
 
@@ -3517,7 +3506,7 @@ public:
           }
         }
         if (IsTailCall)
-          addAnnotation(CallOrJmp, "TC", true);
+          setTailCall(CallOrJmp);
 
         if (CallOrJmp.getOpcode() == X86::CALL64r ||
             CallOrJmp.getOpcode() == X86::CALL64pcrel32) {