- Without frame pointer:
- movm [d2,d3,a2,a3],sp (if needed)
- add <size>,sp
+ - Save the floating-point registers. We have two possible
+ strategies:
+
+ . Save them at fixed offset from the SP:
+
+ fmov fsN,(OFFSETN,sp)
+ fmov fsM,(OFFSETM,sp)
+ ...
+
+ Note that, if OFFSETN happens to be zero, you'll get the
+ different opcode: fmov fsN,(sp)
+
+ . Or, set a0 to the start of the save area, and then use
+ post-increment addressing to save the FP registers.
+
+ mov sp, a0
+ add SIZE, a0
+ fmov fsN,(a0+)
+ fmov fsM,(a0+)
+ ...
+
+ + If the function needs a frame pointer, we set it here.
+
+ mov sp, a3
+
+ + Now we reserve space for the stack frame proper. This could be
+ merged into the `add -SIZE, sp' instruction for FP saves up
+ above, unless we needed to set the frame pointer in the previous
+ step, or the frame is so large that allocating the whole thing at
+ once would put the FP register save slots out of reach of the
+ addressing mode (128 bytes).
+
+ add -SIZE, sp