Hi, I am working on adding support for code-copying to GCC that can be used to safely speed up interpreter-based VMs, as will be presented at GCC Summit:
http://www.gccsummit.org/2007/view_abstract.php?content_key=30 One of the operations I need to perform is to reorder basic blocks in a particular manner. This works fine for example on i386 and other that have HAS_LONG_COND_BRANCH, HAS_LONG_UNCOND_BRANCH set. However on platforms like PPC, after the reordering, some branches are trying to reach destinations beyond their reach and I get errors during the final assembly. The draft of a solution I came up with after a few days of digging in the existing code is this: For each function that has basic blocks reordered for code-copying, Scan all the insn's, find all jumps, For each jump check its destination label, and 1. compute the distance between the jump and the label (if possible use insn_lengths[] form final.c, or build it yourself using get_attr_length()) 2. compare the distance with what can be reached using the Mode (GET_MODE_SIZE, exact_log2()) 3. if Mode won't reach the destination, create an extra BB with an unconditional or indirect jump to the label (like bb-reorder.c) and redirect the original jump to it. Is there an esier way of doing it? (maybe there's mechanisms in GCC that do it already?) What am I missing? Any similar code in GCC I should look at? Thanks, Gregory -- Gregory B. Prokopski <[EMAIL PROTECTED]> Sable Research Group http://www.sable.mcgill.ca Montreal, Quebec, Canada
