Move the support for using .init_array from ARM to the generic

TargetLoweringObjectFileELF. Use this to support it on X86. Unlike ARM,
on X86 it is not easy to find out if .init_array should be used or not, so
the decision is made via TargetOptions and defaults to off.

Add a command line option to llc that enables it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158692 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetOptions.h

@@ -43,7 +43,7 @@ namespace llvm {
           StackAlignmentOverride(0), RealignStack(true),
           DisableJumpTables(false), EnableFastISel(false),
           PositionIndependentExecutable(false), EnableSegmentedStacks(false),
-          TrapFuncName(""), FloatABIType(FloatABI::Default)
+          UseInitArray(false), TrapFuncName(""), FloatABIType(FloatABI::Default)
     {}
 
     /// PrintMachineCode - This flag is enabled when the -print-machineinstrs
@@ -172,6 +172,10 @@ namespace llvm {
 
     unsigned EnableSegmentedStacks : 1;
 
+    /// UseInitArray - Use .init_array instead of .ctors for static
+    /// constructors.
+    unsigned UseInitArray : 1;
+
     /// getTrapFunctionName - If this returns a non-empty string, this means
     /// isel should lower Intrinsic::trap to a call to the specified function
     /// name instead of an ISD::TRAP node.