[SystemZ] Avoid repeated hash lookups (NFC) (#126679)

Author: kazutakahirata

llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp

@@ -688,16 +688,17 @@ void SystemZAsmPrinter::emitInstruction(const MachineInstr *MI) {
     int64_t SrcDisp = MI->getOperand(5).getImm();
 
     SystemZTargetStreamer *TS = getTargetStreamer();
-    MCSymbol *DotSym = nullptr;
-    MCInst ET = MCInstBuilder(TargetInsOpc).addReg(DestReg)
-      .addImm(DestDisp).addImm(1).addReg(SrcReg).addImm(SrcDisp);
+    MCInst ET = MCInstBuilder(TargetInsOpc)
+                    .addReg(DestReg)
+                    .addImm(DestDisp)
+                    .addImm(1)
+                    .addReg(SrcReg)
+                    .addImm(SrcDisp);
     SystemZTargetStreamer::MCInstSTIPair ET_STI(ET, &MF->getSubtarget());
-    SystemZTargetStreamer::EXRLT2SymMap::iterator I =
-        TS->EXRLTargets2Sym.find(ET_STI);
-    if (I != TS->EXRLTargets2Sym.end())
-      DotSym = I->second;
-    else
-      TS->EXRLTargets2Sym[ET_STI] = DotSym = OutContext.createTempSymbol();
+    auto [It, Inserted] = TS->EXRLTargets2Sym.try_emplace(ET_STI);
+    if (Inserted)
+      It->second = OutContext.createTempSymbol();
+    MCSymbol *DotSym = It->second;
     const MCSymbolRefExpr *Dot = MCSymbolRefExpr::create(DotSym, OutContext);
     EmitToStreamer(
         *OutStreamer,