From 7d48c9e2cc0d77630d365efe8fa1803a224a9a0a Mon Sep 17 00:00:00 2001
From: Jeff Law <law@redhat.com>
Date: Fri, 16 Dec 2005 00:03:12 -0700
Subject: [PATCH] tree-ssa-dse.c (dse_optimize_stmt): Correctly handle PHI
nodes which represent a use and definition of the same...
* tree-ssa-dse.c (dse_optimize_stmt): Correctly handle PHI nodes which
represent a use and definition of the same SSA_NAME.
* gcc.dg/tree-ssa/ssa-dse-8.c: New test.
From-SVN: r108630
---
gcc/ChangeLog | 5 +++++
gcc/testsuite/ChangeLog | 4 ++++
gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-8.c | 26 +++++++++++++++++++++++
gcc/tree-ssa-dse.c | 9 ++++++++
4 files changed, 44 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-8.c
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 661e5337a535..d90de63c4a95 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2005-12-16 Jeff Law <law@redhat.com>
+
+ * tree-ssa-dse.c (dse_optimize_stmt): Correctly handle PHI nodes which
+ represent a use and definition of the same SSA_NAME.
+
2005-12-16 Jon Grimm <jgrimm2@us.ibm.com>
Janis Johnson <janis187@us.ibm.com>
Ben Elliston <bje@au.ibm.com>
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 6662c2eaffa0..9c4ba84cbe30 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2005-12-16 Jeff Law <law@redhat.com>
+
+ * gcc.dg/tree-ssa/ssa-dse-8.c: New test.
+
2005-12-16 Andrew Pinski <pinskia@physics.uc.edu>
* objc.dg/gnu-encoding/struct-layout-encoding-1_generate.c (base_types):
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-8.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-8.c
new file mode 100644
index 000000000000..de1d5bb62403
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-8.c
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-dce -fno-tree-ccp -fno-tree-copy-prop -fno-tree-dominator-opts" } */
+
+/* This caused the compiler to enter an infinite loop if copies are not
+ fully propagated. The options are to disable copy propagation and
+ thus expose the bug. */
+
+int foo (void);
+
+struct A {
+ struct B {
+ struct B *n;
+ } *p;
+};
+
+static inline void baz (struct A *a)
+{
+ a->p = a->p->n;
+}
+
+void bar (struct A a)
+{
+ while (foo ())
+ baz (&a);
+ while (foo ());
+}
diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c
index fa3ba960a289..f1cc22ae3102 100644
--- a/gcc/tree-ssa-dse.c
+++ b/gcc/tree-ssa-dse.c
@@ -309,6 +309,15 @@ dse_optimize_stmt (struct dom_walk_data *walk_data,
&& TREE_CODE (use_stmt) == PHI_NODE
&& bitmap_bit_p (dse_gd->stores, get_stmt_uid (use_stmt)))
{
+ /* A PHI node can both define and use the same SSA_NAME if
+ the PHI is at the top of a loop and the PHI_RESULT is
+ a loop invariant and copies have not been fully propagated.
+
+ The safe thing to do is exit assuming no optimization is
+ possible. */
+ if (SSA_NAME_DEF_STMT (PHI_RESULT (use_stmt)) == use_stmt)
+ return;
+
/* Skip past this PHI and loop again in case we had a PHI
chain. */
if (single_imm_use (PHI_RESULT (use_stmt), &use_p, &use_stmt))
--
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