[BOLT] Support for OpNegateRAState - first half

    - when reading binary, drop OpNegateRAState CFIs
    - change CFI State calculation to ignore OpNegateRAState CFIs

Author: bgergely0

bolt/lib/Core/BinaryBasicBlock.cpp

@@ -201,7 +201,11 @@ int32_t BinaryBasicBlock::getCFIStateAtInstr(const MCInst *Instr) const {
       InstrSeen = (&Inst == Instr);
       continue;
     }
-    if (Function->getBinaryContext().MIB->isCFI(Inst)) {
+    // Fix: ignoring OpNegateRAState CFIs here, as they dont have a "State"
+    // number associated with them.
+    if (Function->getBinaryContext().MIB->isCFI(Inst) &&
+        (Function->getCFIFor(Inst)->getOperation() !=
+         MCCFIInstruction::OpNegateRAState)) {
       LastCFI = &Inst;
       break;
     }

bolt/lib/Core/BinaryFunction.cpp

@@ -2596,6 +2596,7 @@ struct CFISnapshot {
   void advanceTo(int32_t State) {
     for (int32_t I = CurState, E = State; I != E; ++I) {
       const MCCFIInstruction &Instr = FDE[I];
+      assert(Instr.getOperation() != MCCFIInstruction::OpNegateRAState);
       if (Instr.getOperation() != MCCFIInstruction::OpRestoreState) {
         update(Instr, I);
         continue;

bolt/lib/Core/Exceptions.cpp

@@ -632,8 +632,10 @@ bool CFIReaderWriter::fillCFIInfoFor(BinaryFunction &Function) const {
       // DW_CFA_GNU_window_save and DW_CFA_GNU_NegateRAState just use the same
       // id but mean different things. The latter is used in AArch64.
       if (Function.getBinaryContext().isAArch64()) {
-        Function.addCFIInstruction(
-            Offset, MCCFIInstruction::createNegateRAState(nullptr));
+        // Fix: not adding OpNegateRAState since the location they are needed
+        // depends on the order of BasicBlocks, which changes during
+        // optimizations. They are generated in InsertNegateRAStatePass after
+        // optimizations instead.
         break;
       }
       if (opts::Verbosity >= 1)