Add support for nest attribute to AArch64 backend

The nest attribute is currently supported on the x86 (32-bit) and x86-64
backends, but not on ARM (32-bit) or AArch64. This patch adds support for
nest to the AArch64 backend.

Register x18 is used by GCC for this purpose and hence is used here.
As discussed on the GCC mailing list the register choice is an ABI issue
and so choosing the same register as GCC means __builtin_call_with_static_chain
is compatible.

Patch by Stephen Cross.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241794 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AArch64/AArch64CallingConvention.td b/lib/Target/AArch64/AArch64CallingConvention.td
index 4691e949838d16a2d8954f2a418e25d523e3961c..815ebef177d87a32b4d6a9c6a1ffb87fd13dd874 100644 (file)
--- a/lib/Target/AArch64/AArch64CallingConvention.td
+++ b/lib/Target/AArch64/AArch64CallingConvention.td
@@ -40,6 +40,11 @@ def CC_AArch64_AAPCS : CallingConv<[
   // slot is 64-bit.
   CCIfByVal<CCPassByVal<8, 8>>,
 
+  // The 'nest' parameter, if any, is passed in X18.
+  // Darwin uses X18 as the platform register and hence 'nest' isn't currently
+  // supported there.
+  CCIfNest<CCAssignToReg<[X18]>>,
+
   CCIfConsecutiveRegs<CCCustom<"CC_AArch64_Custom_Block">>,
 
   // Handle i1, i8, i16, i32, i64, f32, f64 and v2f64 by passing in registers,