X86: use a data driven configuration of Windows x86 libcalls (NFC)

Rather than creating a series of associated calls and ensuring that
everything is lined up, use a table driven approach that ensures that
they two always stay in sync.

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -135,19 +135,24 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
       addBypassSlowDiv(64, 32);
   }
 
-  if (Subtarget.isTargetWindowsMSVC() ||
-      Subtarget.isTargetWindowsItanium()) {
-    // Setup Windows compiler runtime calls.
-    setLibcallName(RTLIB::SDIV_I64, "_alldiv");
-    setLibcallName(RTLIB::UDIV_I64, "_aulldiv");
-    setLibcallName(RTLIB::SREM_I64, "_allrem");
-    setLibcallName(RTLIB::UREM_I64, "_aullrem");
-    setLibcallName(RTLIB::MUL_I64, "_allmul");
-    setLibcallCallingConv(RTLIB::SDIV_I64, CallingConv::X86_StdCall);
-    setLibcallCallingConv(RTLIB::UDIV_I64, CallingConv::X86_StdCall);
-    setLibcallCallingConv(RTLIB::SREM_I64, CallingConv::X86_StdCall);
-    setLibcallCallingConv(RTLIB::UREM_I64, CallingConv::X86_StdCall);
-    setLibcallCallingConv(RTLIB::MUL_I64, CallingConv::X86_StdCall);
+  // Setup Windows compiler runtime calls.
+  if (Subtarget.isTargetWindowsMSVC() || Subtarget.isTargetWindowsItanium()) {
+    static const struct {
+      const RTLIB::Libcall Op;
+      const char * const Name;
+      const CallingConv::ID CC;
+    } LibraryCalls[] = {
+      { RTLIB::SDIV_I64, "_alldiv", CallingConv::X86_StdCall },
+      { RTLIB::UDIV_I64, "_aulldiv", CallingConv::X86_StdCall },
+      { RTLIB::SREM_I64, "_allrem", CallingConv::X86_StdCall },
+      { RTLIB::UREM_I64, "_aullrem", CallingConv::X86_StdCall },
+      { RTLIB::MUL_I64, "_allmul", CallingConv::X86_StdCall },
+    };
+
+    for (const auto &LC : LibraryCalls) {
+      setLibcallName(LC.Op, LC.Name);
+      setLibcallCallingConv(LC.Op, LC.CC);
+    }
   }
 
   if (Subtarget.getTargetTriple().isOSMSVCRT()) {