AArch64: Default AArch64Subtarget::ReserveX18 to true on darwin

Darwin reserves x18, so it's never ABI compliant to generate code that
uses it. Set the default value based on the OS part of the triple
rather than forcing front-ends to set the +reserve-x18 target feature
in order to build correct code for Darwin.

This will make r243310 redundant, so I'll revert that shortly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253102 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AArch64/AArch64Subtarget.cpp b/lib/Target/AArch64/AArch64Subtarget.cpp
index 88af9602322dc18e8262b2866bc7450da3ca5f0f..14ad44db800e28c8dbdda9a9834febe8a4f94441 100644 (file)
--- a/lib/Target/AArch64/AArch64Subtarget.cpp
+++ b/lib/Target/AArch64/AArch64Subtarget.cpp
@@ -53,8 +53,9 @@ AArch64Subtarget::AArch64Subtarget(const Triple &TT, const std::string &CPU,
     : AArch64GenSubtargetInfo(TT, CPU, FS), ARMProcFamily(Others),
       HasV8_1aOps(false), HasFPARMv8(false), HasNEON(false), HasCrypto(false),
       HasCRC(false), HasPerfMon(false), HasZeroCycleRegMove(false),
-      HasZeroCycleZeroing(false), StrictAlign(false), ReserveX18(false),
-      IsLittle(LittleEndian), CPUString(CPU), TargetTriple(TT), FrameLowering(),
+      HasZeroCycleZeroing(false), StrictAlign(false),
+      ReserveX18(TT.isOSDarwin()), IsLittle(LittleEndian), CPUString(CPU),
+      TargetTriple(TT), FrameLowering(),
       InstrInfo(initializeSubtargetDependencies(FS)), TSInfo(),
       TLInfo(TM, *this) {}