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

[Iain Buclaw <ibuclaw@gcc.gnu.org>]

https://gcc.gnu.org/g:17f7ee9e2d6feac3b464c9dd92296d700cbe27cc

commit 17f7ee9e2d6feac3b464c9dd92296d700cbe27cc
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 | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/libphobos/libdruntime/core/thread/fiber.d b/libphobos/libdruntime/core/thread/fiber.d
index 6430d7189c0..1161914a8a2 100644
--- a/libphobos/libdruntime/core/thread/fiber.d
+++ b/libphobos/libdruntime/core/thread/fiber.d
@@ -1357,6 +1357,33 @@ private:
 
             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;
+            }
+
+            assert( (cast(size_t) pstack & 0x0f) == 0 );
+        }
         else version (AsmMIPS_O32_Posix)
         {
             version (StackGrowsDown) {}