[BOLT] Add createCondBranch() and createLongUncondBranch() (#85315)

Add MCPlusBuilder interface for creating two new branch types.

Author: maksfb

bolt/include/bolt/Core/MCPlusBuilder.h

@@ -1558,6 +1558,13 @@ class MCPlusBuilder {
     llvm_unreachable("not implemented");
   }
 
+  /// Create a version of unconditional jump that has the largest span for a
+  /// single instruction with direct target.
+  virtual void createLongUncondBranch(MCInst &Inst, const MCSymbol *Target,
+                                      MCContext *Ctx) const {
+    llvm_unreachable("not implemented");
+  }
+
   /// Creates a new call instruction in Inst and sets its operand to
   /// Target.
   virtual void createCall(MCInst &Inst, const MCSymbol *Target,
@@ -1675,6 +1682,12 @@ class MCPlusBuilder {
     return Inst.getOpcode() == TargetOpcode::CFI_INSTRUCTION;
   }
 
+  /// Create a conditional branch with a target-specific conditional code \p CC.
+  virtual void createCondBranch(MCInst &Inst, const MCSymbol *Target,
+                                unsigned CC, MCContext *Ctx) const {
+    llvm_unreachable("not implemented");
+  }
+
   /// Reverses the branch condition in Inst and update its taken target to TBB.
   ///
   /// Returns true on success.

bolt/lib/Target/X86/X86MCPlusBuilder.cpp

@@ -2734,6 +2734,14 @@ class X86MCPlusBuilder : public MCPlusBuilder {
         MCSymbolRefExpr::create(TBB, MCSymbolRefExpr::VK_None, *Ctx)));
   }
 
+  void createLongUncondBranch(MCInst &Inst, const MCSymbol *Target,
+                              MCContext *Ctx) const override {
+    Inst.setOpcode(X86::JMP_4);
+    Inst.clear();
+    Inst.addOperand(MCOperand::createExpr(
+        MCSymbolRefExpr::create(Target, MCSymbolRefExpr::VK_None, *Ctx)));
+  }
+
   void createCall(MCInst &Inst, const MCSymbol *Target,
                   MCContext *Ctx) override {
     Inst.setOpcode(X86::CALL64pcrel32);
@@ -2759,6 +2767,15 @@ class X86MCPlusBuilder : public MCPlusBuilder {
     Inst.setOpcode(X86::TRAP);
   }
 
+  void createCondBranch(MCInst &Inst, const MCSymbol *Target, unsigned CC,
+                        MCContext *Ctx) const override {
+    Inst.setOpcode(X86::JCC_1);
+    Inst.clear();
+    Inst.addOperand(MCOperand::createExpr(
+        MCSymbolRefExpr::create(Target, MCSymbolRefExpr::VK_None, *Ctx)));
+    Inst.addOperand(MCOperand::createImm(CC));
+  }
+
   bool reverseBranchCondition(MCInst &Inst, const MCSymbol *TBB,
                               MCContext *Ctx) const override {
     unsigned InvCC = getInvertedCondCode(getCondCode(Inst));