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re PR tree-optimization/26251 (code size increase with -Os)

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PR tree-optimization/26251
	* tree-ssa-threadupdate.c (redirection_block_p): New function.
	(thread_block): When optimizing for size refuse to thread jumps
	that would require duplication of blocks other than redirection
	blocks.

From-SVN: r115150
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Roger Sayle 2006-07-03 14:35:13 +00:00 committed by Roger Sayle
parent 3a3977a810
commit 31a9760af0
2 changed files with 47 additions and 1 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2006-07-03 Roger Sayle <roger@eyesopen.com>
PR tree-optimization/26251
* tree-ssa-threadupdate.c (redirection_block_p): New function.
(thread_block): When optimizing for size refuse to thread jumps
that would require duplication of blocks other than redirection
blocks.
2006-07-03 Paolo Bonzini <bonzini@gnu.org>
* configure.ac: Fix thinko in previous check-in.

40
gcc/tree-ssa-threadupdate.c
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@ -1,5 +1,5 @@
/* Thread edges through blocks and update the control flow and SSA graphs.
Copyright (C) 2004, 2005 Free Software Foundation, Inc.
Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
This file is part of GCC.
@ -652,6 +652,33 @@ redirect_edges (void **slot, void *data)
return 1;
}
/* Return true if this block has no executable statements other than
a simple ctrl flow instruction. When the number of outgoing edges
is one, this is equivalent to a "forwarder" block. */
static bool
redirection_block_p (basic_block bb)
{
block_stmt_iterator bsi;
/* Advance to the first executable statement. */
bsi = bsi_start (bb);
while (!bsi_end_p (bsi)
&& (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR
|| IS_EMPTY_STMT (bsi_stmt (bsi))))
bsi_next (&bsi);
/* Check if this is an empty block. */
if (bsi_end_p (bsi))
return true;
/* Test that we've reached the terminating control statement. */
return bsi_stmt (bsi)
&& (TREE_CODE (bsi_stmt (bsi)) == COND_EXPR
|| TREE_CODE (bsi_stmt (bsi)) == GOTO_EXPR
|| TREE_CODE (bsi_stmt (bsi)) == SWITCH_EXPR);
}
/* BB is a block which ends with a COND_EXPR or SWITCH_EXPR and when BB
is reached via one or more specific incoming edges, we know which
outgoing edge from BB will be traversed.
@ -699,6 +726,17 @@ thread_block (basic_block bb)
be threaded to a duplicate of BB. */
bool all = true;
/* If optimizing for size, only thread this block if we don't have
to duplicate it or it's an otherwise empty redirection block. */
if (optimize_size
&& EDGE_COUNT (bb->preds) > 1
&& !redirection_block_p (bb))
{
FOR_EACH_EDGE (e, ei, bb->preds)
e->aux = NULL;
return false;
}
/* To avoid scanning a linear array for the element we need we instead
use a hash table. For normal code there should be no noticeable
difference. However, if we have a block with a large number of