From 72b8d451f1b0c3bef4b3afc688ada5d5175d97d0 Mon Sep 17 00:00:00 2001
From: Zdenek Dvorak <rakdver@atrey.karlin.mff.cuni.cz>
Date: Sat, 8 Mar 2003 10:47:28 +0100
Subject: gcse.c (bypass_block, [...]): Do not create irreducible loops.
* gcse.c (bypass_block, bypass_conditional_jumps): Do not create
irreducible loops.
* loop-unroll.c (unroll_loop_runtime_iterations): Update irreducible
loops info correctly.
From-SVN: r63980
---
gcc/gcse.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
(limited to 'gcc/gcse.c')
diff --git a/gcc/gcse.c b/gcc/gcse.c
index f5bb66d0053..f0e588ecd49 100644
--- a/gcc/gcse.c
+++ b/gcc/gcse.c
@@ -4759,6 +4759,7 @@ bypass_block (bb, setcc, jump)
rtx insn, note;
edge e, enext;
int i, change;
+ int may_be_loop_header;
insn = (setcc != NULL) ? setcc : jump;
@@ -4769,6 +4770,14 @@ bypass_block (bb, setcc, jump)
if (note)
find_used_regs (&XEXP (note, 0), NULL);
+ may_be_loop_header = false;
+ for (e = bb->pred; e; e = e->pred_next)
+ if (e->flags & EDGE_DFS_BACK)
+ {
+ may_be_loop_header = true;
+ break;
+ }
+
change = 0;
for (e = bb->pred; e; e = enext)
{
@@ -4780,6 +4789,13 @@ bypass_block (bb, setcc, jump)
if (e->src->index >= bypass_last_basic_block)
continue;
+ /* The irreducible loops created by redirecting of edges entering the
+ loop from outside would decrease effectivity of some of the following
+ optimalizations, so prevent this. */
+ if (may_be_loop_header
+ && !(e->flags & EDGE_DFS_BACK))
+ continue;
+
for (i = 0; i < reg_use_count; i++)
{
struct reg_use *reg_used = ®_use_table[i];
@@ -4866,6 +4882,7 @@ bypass_conditional_jumps ()
return 0;
bypass_last_basic_block = last_basic_block;
+ mark_dfs_back_edges ();
changed = 0;
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb->next_bb,
--
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