[gcc(refs/users/iains/heads/d-for-darwin)] D, Linux : Add implementation for PPC64 init stack.

[Iain D Sandoe <iains@gcc.gnu.org>]

https://gcc.gnu.org/g:4c2c9cdb6e14f30593288c012254aeecc25c745d

commit 4c2c9cdb6e14f30593288c012254aeecc25c745d
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Fri Dec 11 00:53:40 2020 +0000

    D, Linux : Add implementation for PPC64 init stack.
    
    This provides an initStack entry for 'Posix' PPC64 case.

Diff:
---
 libphobos/libdruntime/core/thread/fiber.d | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/libphobos/libdruntime/core/thread/fiber.d b/libphobos/libdruntime/core/thread/fiber.d
index 64e90182596..4ae0d033be1 100644
--- a/libphobos/libdruntime/core/thread/fiber.d
+++ b/libphobos/libdruntime/core/thread/fiber.d
@@ -1395,6 +1395,31 @@ private:
               *cast(size_t*)(pstack + wsize) = cast(size_t) Thread.getThis().m_addr;
             assert( (cast(size_t) pstack & 0x0f) == 0 );
         }
+        else version (AsmPPC64_Posix)
+        {
+            version (StackGrowsDown)
+            {
+                pstack -= long.sizeof * 5;
+            }
+            else
+            {
+                pstack += long.sizeof * 5;
+            }
+
+            push( cast(size_t) &fiber_entryPoint );     // link register
+            push( 0x00000000_00000000 );                // control register
+            push( 0x00000000_00000000 );                // old stack pointer
+
+            // GPR values
+            version (StackGrowsDown)
+            {
+                pstack -= long.sizeof * 20;
+            }
+            else
+            {
+                pstack += long.sizeof * 20;
+            }
+        }
         else version (AsmMIPS_O32_Posix)
         {
             version (StackGrowsDown) {}