mirrors/gcc
0
0
Fork 0
mirror of https://gcc.gnu.org/git/gcc.git synced 2024-11-28 06:14:10 +08:00
Code Issues Actions Packages Projects Releases Wiki Activity

dce.c (delete_unmarked_insns): Reversed the order that insns are examined before deleting them.

Browse Source 
2009-01-16  Kenneth Zadeck <zadeck@naturalbridge.com>

	* dce.c (delete_unmarked_insns): Reversed the order that insns are
	examined before deleting them.

From-SVN: r143433
This commit is contained in:
Kenneth Zadeck 2009-01-16 13:41:11 +00:00 committed by Kenneth Zadeck
parent c433cb14ae
commit cd3f172908
2 changed files with 25 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
gcc/ChangeLog
View File

@ -1,3 +1,8 @@
2009-01-16 Kenneth Zadeck <zadeck@naturalbridge.com>
* dce.c (delete_unmarked_insns): Reversed the order that insns are
examined before deleting them.
2009-01-16 Richard Earnshaw <rearnsha@arm.com>
* function.c (aggregate_value_p): Correctly extract the function

29
gcc/dce.c
View File

@ -510,8 +510,8 @@ delete_unmarked_insns (void)
rtx insn, next;
bool must_clean = false;
FOR_EACH_BB (bb)
FOR_BB_INSNS_SAFE (bb, insn, next)
FOR_EACH_BB_REVERSE (bb)
FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next)
if (INSN_P (insn))
{
/* Always delete no-op moves. */
@ -522,13 +522,24 @@ delete_unmarked_insns (void)
else if (marked_insn_p (insn))
continue;
/* Beware that reaching a dbg counter limit here can rarely
result in miscompiled file. This occurs when a group of
insns must be deleted together. Currently this only
can happen on non-looping pure and constant calls
on machines where ACCUMULATE_OUTGOING_ARGS is true. By
using the dbg_cnt, it is possible to remove the call, but
leave the argument pushes to the stack. */
/* Beware that reaching a dbg counter limit here can result
in miscompiled file. This occurs when a group of insns
must be deleted together, typically because the kept insn
depends on the output from the deleted insn. Deleting
this insns in reverse order (both at the bb level and
when looking at the blocks) minimizes this, but does not
eliminate it, since it is possible for the using insn to
be top of a block and the producer to be at the bottom of
the block. However, in most cases this will only result
in an uninitialized use of an insn that is dead anyway.
However, there is one rare case that will cause a
miscompile: deletion of non-looping pure and constant
calls on a machine where ACCUMULATE_OUTGOING_ARGS is true.
In this case it is possible to remove the call, but leave
the argument pushes to the stack. Because of the changes
to the stack pointer, this will almost always lead to a
miscompile. */
if (!dbg_cnt (dce))
continue;