Tidy up interface_to_C.

diff --git a/src/microcode/cmpauxmd/aarch64.m4 b/src/microcode/cmpauxmd/aarch64.m4
index e0b52a664b3f73e7b14c995c5f63ead914a6e0c1..e6f6cf35a2c1ef54c9fb277618d3eea09bdd5582 100644 (file)
--- a/src/microcode/cmpauxmd/aarch64.m4
+++ b/src/microcode/cmpauxmd/aarch64.m4
@@ -124,7 +124,7 @@ END(C_to_interface)
 // Returning to C from Scheme
 ///////////////////////////////////////////////////////////////////////////////
 
-       // void interface_to_C (long code@x0)
+       // void interface_to_C (long code@x1, void * garbage@x17)
        //
        //      When a utility returns and it needs to fall back to the
        //      interpreter, it directs scheme_to_interface_return to
@@ -133,17 +133,17 @@ END(C_to_interface)
        //
        //      Steps:
        //
-       //      1. Tear down the Scheme registers.
-       //      2. Restore the return address, frame pointer, and
+       //      1. Restore the return address, frame pointer, and
        //         callee-saves registers.
-       //      3. Return.
+       //      2. Return.
+       //
+       //      The mutable Scheme registers -- FREE, SSP -- will have
+       //      alreay been saved by scheme_to_interface on earlier
+       //      entry to C.
        //
 GLOBAL(interface_to_C)
-       // Tear down the Scheme registers.
-       ADRL(x1,Free)                   // address of Free pointer
-       str     FREE, [x1]              // store current Free pointer
-       ADRL(x1,stack_pointer)          // address of stack pointer
-       str     SSP, [x1]               // store current stack pointer
+       // Set return value.
+       mov     x0, x1
 
        // Restore callee-saves registers.
        ldp     x19, x20, [sp,#16]