[MC,COFF] Don't evaluate end() every iteration

In accordance with https://llvm.org/docs/CodingStandards.html
we shouldn't do this.

Author: chestnykh

llvm/lib/MC/XCOFFObjectWriter.cpp

@@ -1385,23 +1385,25 @@ void XCOFFObjectWriter::addExceptionEntry(
 unsigned XCOFFObjectWriter::getExceptionSectionSize() {
   unsigned EntryNum = 0;
 
-  for (auto it = ExceptionSection.ExceptionTable.begin();
-       it != ExceptionSection.ExceptionTable.end(); ++it)
+  for (auto I = ExceptionSection.ExceptionTable.begin(),
+            E = ExceptionSection.ExceptionTable.end();
+       I != E; ++I)
     // The size() gets +1 to account for the initial entry containing the
     // symbol table index.
-    EntryNum += it->second.Entries.size() + 1;
+    EntryNum += I->second.Entries.size() + 1;
 
   return EntryNum * (is64Bit() ? XCOFF::ExceptionSectionEntrySize64
                                : XCOFF::ExceptionSectionEntrySize32);
 }
 
 unsigned XCOFFObjectWriter::getExceptionOffset(const MCSymbol *Symbol) {
   unsigned EntryNum = 0;
-  for (auto it = ExceptionSection.ExceptionTable.begin();
-       it != ExceptionSection.ExceptionTable.end(); ++it) {
-    if (Symbol == it->second.FunctionSymbol)
+  for (auto I = ExceptionSection.ExceptionTable.begin(),
+            E = ExceptionSection.ExceptionTable.end();
+       I != E; ++I) {
+    if (Symbol == I->second.FunctionSymbol)
       break;
-    EntryNum += it->second.Entries.size() + 1;
+    EntryNum += I->second.Entries.size() + 1;
   }
   return EntryNum * (is64Bit() ? XCOFF::ExceptionSectionEntrySize64
                                : XCOFF::ExceptionSectionEntrySize32);
@@ -1667,17 +1669,18 @@ void XCOFFObjectWriter::writeSectionForDwarfSectionEntry(
 void XCOFFObjectWriter::writeSectionForExceptionSectionEntry(
     const MCAssembler &Asm, ExceptionSectionEntry &ExceptionEntry,
     uint64_t &CurrentAddressLocation) {
-  for (auto it = ExceptionEntry.ExceptionTable.begin();
-       it != ExceptionEntry.ExceptionTable.end(); it++) {
+  for (auto I = ExceptionEntry.ExceptionTable.begin(),
+            E = ExceptionEntry.ExceptionTable.end();
+       I != E; ++I) {
     // For every symbol that has exception entries, you must start the entries
     // with an initial symbol table index entry
-    W.write<uint32_t>(SymbolIndexMap[it->second.FunctionSymbol]);
+    W.write<uint32_t>(SymbolIndexMap[I->second.FunctionSymbol]);
     if (is64Bit()) {
       // 4-byte padding on 64-bit.
       W.OS.write_zeros(4);
     }
     W.OS.write_zeros(2);
-    for (auto &TrapEntry : it->second.Entries) {
+    for (auto &TrapEntry : I->second.Entries) {
       writeWord(TrapEntry.TrapAddress);
       W.write<uint8_t>(TrapEntry.Lang);
       W.write<uint8_t>(TrapEntry.Reason);