* config/mmix/mmix.md ("return"): New pattern.
* config/mmix/mmix.h (TARGET_MASK_USE_RETURN_INSN)
(TARGET_USE_RETURN_INSN): New macros.
(TARGET_DEFAULT): Include TARGET_MASK_USE_RETURN_INSN.
(TARGET_SWITCHES): Add -msingle-exit and -mno-single-exit.
* config/mmix/mmix.c (MMIX_OUTPUT_REGNO): Fix spacing.
(MMIX_POP_ARGUMENT): New macro.
(mmix_target_asm_function_prologue): When no epilogue is executed,
just emit a blank line. Use MMIX_POP_ARGUMENT with final POP insn.
(mmix_print_operand) <case '.'>: New case.
(mmix_print_operand_punct_valid_p): Match '.'.
(mmix_use_simple_return): New function.
* config/mmix/mmix-protos.h (mmix_use_simple_return): Prototype.
* doc/invoke.texi (Option Summary) <MMIX Summary>: Add
-msingle-exit, -mno-single-exit.
(MMIX Options): Ditto.
From-SVN: r55121
