PR 65658 shows a case where we fail to thread jumps in a block that is
trivially threadable and would generate no code if threaded. That in
turn results in inefficient code and a false positive from -Wuninitialized.
The problem is the problem block has a clobber statement and
redirection_block_p thus rejects the block as a redirection block. That
in turn causes the recorded jump threads to be pruned.
Fixed by handling clobber statements in redirection-block_p.
Bootstrapped and regression tested on x86-linux-gnu. Installed on the
trunk.
Jeff
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a34e846..9d8c2bc 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2015-04-20 Jeff Law <l...@redhat.com>
+
+ PR tree-optimization/65658
+ * tree-ssa-threadupdate.c (redirection_block_p): Ignore clobber
+ statements too.
+
2015-04-20 Alan Lawrence <alan.lawre...@arm.com>
* config/aarch64/aarch64.c (aarch64_simd_emit_pair_result_insn): Delete.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 248ffc8..e768f57 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-04-20 Jeff Law <l...@redhat.com>
+
+ PR tree-optimization/65658
+ * gcc.dg/pr65658.c: New test.
+
2015-04-20 Alan Lawrence <alan.lawre...@arm.com>
PR target/64134
diff --git a/gcc/testsuite/gcc.dg/pr65658.c b/gcc/testsuite/gcc.dg/pr65658.c
new file mode 100644
index 0000000..cce0f2a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr65658.c
@@ -0,0 +1,111 @@
+/* { dg-do compile } */
+/* { dg-options "-Wuninitialized -O2 -Wno-implicit" } */
+
+extern int optind;
+struct undefinfo
+{
+ unsigned long l1;
+ unsigned long l2;
+};
+struct undeffoo
+{
+ char a[64];
+ long b[4];
+ int c[33];
+};
+struct problem
+{
+ unsigned long l1;
+ unsigned long l2;
+ unsigned long l3;
+ unsigned long l4;
+};
+static unsigned int undef1, undef2, undef3, undef4, undef5, undef6;
+static void *undefvp1;
+extern struct undefinfo undefinfo;
+static int
+undefinit1 (void)
+{
+ struct undeffoo foo;
+ int i;
+ for (i = 0; i < 2000; i++)
+ {
+ undef6++;
+ external_function5 (((void *) 0), 0, (void *) &foo);
+ }
+}
+
+static int
+undefinit2 (void *problemp, unsigned long problem)
+{
+ int ret, u;
+ if (undefinit1 ())
+ return 1;
+ if (fn10 ())
+ return 1;
+ for (u = 0; u < undef6; u++)
+ {
+ ret = external_function1 (3 + u * 10, 10);
+ if (ret)
+ return ret;
+ external_function6 (0, 0, 0, problemp + problem);
+ return 1;
+ }
+}
+
+static int
+fn6 (struct undefinfo *uip, struct problem *problem)
+{
+ unsigned long amt;
+ if (external_function3 (((void *) 0), ((void *) 0), &amt, 0, 0))
+ return 1;
+ problem->l1 = (unsigned long) undefvp1;
+ problem->l4 = uip->l1;
+ problem->l3 = uip->l2;
+ return 0;
+}
+
+static int
+setup (void)
+{
+ struct problem problem;
+ if (fn6 (&undefinfo, &problem))
+ return 1;
+ if (fn2 ())
+ return 1;
+ if (fn4 (101))
+ return 1;
+ if (undefinit2 ((void *) problem.l1, problem.l3 * 4)) /* { dg-bogus
"problem.l3" "uninitialized variable warning" } */
+ return 1;
+}
+
+int
+main (int argc, char **argv)
+{
+ int optc;
+ if (external_function (1))
+ return 1;
+ if (external_function (1))
+ return 1;
+ if (external_function (1))
+ return 1;
+ while ((optc =
+ getopt_long (argc, argv, ((void *) 0), ((void *) 0),
+ ((void *) 0))) != -1)
+ {
+ switch (optc)
+ {
+ case 0:
+ break;
+ case 'F':
+ external_function (1);
+ default:
+ return 1;
+ }
+ }
+ if ((optind != 99))
+ {
+ return 1;
+ }
+ setup ();
+}
diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c
index 709b16e..9f263bd 100644
--- a/gcc/tree-ssa-threadupdate.c
+++ b/gcc/tree-ssa-threadupdate.c
@@ -1449,7 +1449,9 @@ redirection_block_p (basic_block bb)
while (!gsi_end_p (gsi)
&& (gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL
|| is_gimple_debug (gsi_stmt (gsi))
- || gimple_nop_p (gsi_stmt (gsi))))
+ || gimple_nop_p (gsi_stmt (gsi))
+ || (gimple_code (gsi_stmt (gsi)) == GIMPLE_ASSIGN
+ && gimple_clobber_p (gsi_stmt (gsi)))))
gsi_next (&gsi);
/* Check if this is an empty block. */
