| Message ID | 005101cf3c43$4f50e250$edf2a6f0$@arm.com |
|---|---|
| State | New |
| Headers | show |
On Mon, Mar 10, 2014 at 10:29 AM, bin.cheng <bin.cheng@arm.com> wrote: > Hi, > When I investigating PR60363 which is caused by previous patch for PR60280, > I found there is a latent bug in remove_forwarder_block_with_phi because GCC > doesn't update loop's latch information. Without this patch, cfgcleanup > facility will remove and rebuild the loop structure, resulting in loss of > loop meta information. > > This patch is just an obvious pickup, but it isn't intended to fix pr60363. > > Test on cortex-m3 > Bootstrap and test on x86_64 > > Is it OK? Ok. Thanks, Richard. > > 2014-03-10 Bin Cheng <bin.cheng@arm.com> > > * tree-cfgcleanup.c (remove_forwarder_block_with_phi): Record > bb's single pred and update the father loop's latch info later.
Index: gcc/tree-cfgcleanup.c =================================================================== --- gcc/tree-cfgcleanup.c (revision 208447) +++ gcc/tree-cfgcleanup.c (working copy) @@ -820,6 +820,12 @@ remove_forwarder_block_with_phi (basic_block bb) && DECL_NONLOCAL (gimple_label_label (label))) return false; + /* Record bb's single pred in case we need to update the father + loop's latch information later. */ + basic_block pred = NULL; + if (single_pred_p (bb)) + pred = single_pred (bb); + /* Redirect each incoming edge to BB to DEST. */ while (EDGE_COUNT (bb->preds) > 0) { @@ -904,6 +910,11 @@ remove_forwarder_block_with_phi (basic_block bb) set_immediate_dominator (CDI_DOMINATORS, dest, dom); + /* Adjust latch infomation of BB's parent loop as otherwise + the cfg hook has a hard time not to kill the loop. */ + if (current_loops && bb->loop_father->latch == bb) + bb->loop_father->latch = pred; + /* Remove BB since all of BB's incoming edges have been redirected to DEST. */ delete_basic_block (bb);