sequenceTop :: NatCmmTop -> NatCmmTop
sequenceTop top@(CmmData _ _) = top
sequenceTop (CmmProc info lbl params blocks) =
- CmmProc info lbl params (sequenceBlocks blocks)
+ CmmProc info lbl params (makeFarBranches $ sequenceBlocks blocks)
-- The algorithm is very simple (and stupid): we make a graph out of
-- the blocks where there is an edge from one block to another iff the
| id == id' = (True, (block,id,out) : reverse accum ++ rest)
| otherwise = reorder id (b:accum) rest
+
+-- -----------------------------------------------------------------------------
+-- Making far branches
+
+-- Conditional branches on PowerPC are limited to +-32KB; if our Procs get too
+-- big, we have to work around this limitation.
+
+makeFarBranches :: [NatBasicBlock] -> [NatBasicBlock]
+
+#if powerpc_TARGET_ARCH
+makeFarBranches blocks
+ | last blockAddresses < nearLimit = blocks
+ | otherwise = zipWith handleBlock blockAddresses blocks
+ where
+ blockAddresses = scanl (+) 0 $ map blockLen blocks
+ blockLen (BasicBlock _ instrs) = length instrs
+
+ handleBlock addr (BasicBlock id instrs)
+ = BasicBlock id (zipWith makeFar [addr..] instrs)
+
+ makeFar addr (BCC ALWAYS tgt) = BCC ALWAYS tgt
+ makeFar addr (BCC cond tgt)
+ | abs (addr - targetAddr) >= nearLimit
+ = BCCFAR cond tgt
+ | otherwise
+ = BCC cond tgt
+ where Just targetAddr = lookupUFM blockAddressMap tgt
+ makeFar addr other = other
+
+ nearLimit = 7000 -- 8192 instructions are allowed; let's keep some
+ -- distance, as we have a few pseudo-insns that are
+ -- pretty-printed as multiple instructions,
+ -- and it's just not worth the effort to calculate
+ -- things exactly
+
+ blockAddressMap = listToUFM $ zip (map blockId blocks) blockAddresses
+#else
+makeFarBranches = id
+#endif
+
-- -----------------------------------------------------------------------------
-- Instruction selection