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[PR debug/46782] Skip debug insns in try_forward_edges
- From: Alexandre Oliva <aoliva at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Wed, 08 Dec 2010 02:06:32 -0200
- Subject: [PR debug/46782] Skip debug insns in try_forward_edges
At -O0, we merge blocks or not depending on locus information present at
the last insn in a block and the entry locus of the subsequent block.
We shouldn't use the locus of a debug insn for this compare, lest we may
end up not merging blocks that, with -g0, we would.
This seldom occurs in practice, since this patch is only active at -O0,
and -fvar-tracking is disabled by default at -O0, even if -g is enabled.
However, since it's possible to explicitly activate -fvar-tracking (and
-fvar-tracking-assignments), even at -O0, we shouldn't generate
different executable code if the user does this.
The patch below was regstrapped on x86_64-linux-gnu. Ok to install?
for gcc/ChangeLog
from Alexandre Oliva <aoliva@redhat.com>
PR debug/46782
* cfgcleanup.c (try_forward_edges): Skip debug insns.
for gcc/testsuite/ChangeLog
from Alexandre Oliva <aoliva@redhat.com>
PR debug/46782
* gcc.dg/debug/pr46782.c: New.
Index: gcc/cfgcleanup.c
===================================================================
--- gcc/cfgcleanup.c.orig 2010-12-06 12:34:03.311495403 -0200
+++ gcc/cfgcleanup.c 2010-12-06 12:34:04.925493962 -0200
@@ -487,11 +487,17 @@ try_forward_edges (int mode, basic_block
new_target = NULL;
else
{
+ rtx last;
+
if (new_locus)
locus = new_locus;
- new_locus = INSN_P (BB_END (target))
- ? INSN_LOCATOR (BB_END (target)) : 0;
+ last = BB_END (target);
+ if (DEBUG_INSN_P (last))
+ last = prev_nondebug_insn (last);
+
+ new_locus = last && INSN_P (last)
+ ? INSN_LOCATOR (last) : 0;
if (new_locus && locus && !locator_eq (new_locus, locus))
new_target = NULL;
Index: gcc/testsuite/gcc.dg/debug/pr46782.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gcc/testsuite/gcc.dg/debug/pr46782.c 2010-12-06 12:34:43.712495319 -0200
@@ -0,0 +1,11 @@
+/* PR debug/46782 */
+/* { dg-do compile } */
+/* { dg-options "-w -O0 -fvar-tracking -fcompare-debug" } */
+
+void foo (int i)
+{
+ if (i)
+ i++;
+ while (i)
+ ;
+}
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer