diff options
Diffstat (limited to 'gcc/tree-cfgcleanup.c')
| -rw-r--r-- | gcc/tree-cfgcleanup.c | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/gcc/tree-cfgcleanup.c b/gcc/tree-cfgcleanup.c index 7e719c1..6f8b1c0 100644 --- a/gcc/tree-cfgcleanup.c +++ b/gcc/tree-cfgcleanup.c @@ -743,6 +743,39 @@ merge_phi_nodes (void) nodes at BB. */ *current++ = bb; } + else + { + tree phi; + + /* BB dominates DEST. There may be many users of the PHI + nodes in BB. However, there is still a trivial case we + can handle. If the result of every PHI in BB is used + only by a PHI in DEST, then we can trivially merge the + PHI nodes from BB into DEST. */ + for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) + { + tree result = PHI_RESULT (phi); + int num_uses = num_imm_uses (result); + use_operand_p imm_use; + tree use_stmt; + + /* If the PHI's result is never used, then we can just + ignore it. */ + if (num_uses == 0) + continue; + + /* Get the single use of the result of this PHI node. */ + if (!single_imm_use (result, &imm_use, &use_stmt) + || TREE_CODE (use_stmt) != PHI_NODE + || bb_for_stmt (use_stmt) != dest) + break; + } + + /* If the loop above iterated thorugh all the PHI nodes + in BB, then we can merge the PHIs from BB into DEST. */ + if (!phi) + *current++ = bb; + } } /* Now let's drain WORKLIST. */ |