When optimize_unreachable was moved from fab to forwprop, I missed that due to
the integrated copy prop, we might end up with an already true branch leading
to a __builtin_unreachable block. optimize_unreachable would switch around
the if and things go down hill from there since the other edge was already
marked as non-executable, forwprop didn't process those blocks and didn't
do copy prop into that block and the original assignment statement was removed.
This fixes the problem by having optimize_unreachable not touch the if
statement was already changed to true/false.
Note I placed the testcase in gcc.c-torture/compile as gcc.dg/torture
is NOT currently testing -Og (see PR 122450 for that).
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/122588
gcc/ChangeLog:
* tree-ssa-forwprop.cc (optimize_unreachable): Don't touch
if the condition was already true or false.
gcc/testsuite/ChangeLog:
* gcc.c-torture/compile/pr122588-1.c: New test.
Signed-off-by: Andrew Pinski <[email protected]>
---
.../gcc.c-torture/compile/pr122588-1.c | 25 +++++++++++++++++++
gcc/tree-ssa-forwprop.cc | 7 +++++-
2 files changed, 31 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr122588-1.c
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr122588-1.c
b/gcc/testsuite/gcc.c-torture/compile/pr122588-1.c
new file mode 100644
index 00000000000..43ec621512c
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr122588-1.c
@@ -0,0 +1,25 @@
+/* Disable warnings about __sync_nand_and_fetch. */
+/* { dg-options "-w" } */
+/* PR tree-optimization/122588 */
+
+int i;
+char c;
+
+static inline __attribute__((__always_inline__))
+void foo0 (int a)
+{
+l5:
+ __sync_nand_and_fetch (&i, 0);
+ int x = __builtin_memcmp_eq (&a, 0, 4);
+ if (__builtin_iseqsig (x, 0.))
+ goto l5;
+ if (a)
+ __builtin_unreachable ();
+ c = a;
+}
+
+int
+main ()
+{
+ foo0 (1);
+}
diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
index ae7f0e770ba..9f8d4ad3b44 100644
--- a/gcc/tree-ssa-forwprop.cc
+++ b/gcc/tree-ssa-forwprop.cc
@@ -5080,7 +5080,12 @@ optimize_unreachable (basic_block bb)
stmt = gsi_stmt (gsi);
if (gcond *cond_stmt = dyn_cast <gcond *> (stmt))
{
- if (e->flags & EDGE_TRUE_VALUE)
+ /* If the condition is already true/false
+ ignore it. This can happen during copy prop of forwprop. */
+ if (gimple_cond_true_p (cond_stmt)
+ || gimple_cond_false_p (cond_stmt))
+ continue;
+ else if (e->flags & EDGE_TRUE_VALUE)
gimple_cond_make_false (cond_stmt);
else if (e->flags & EDGE_FALSE_VALUE)
gimple_cond_make_true (cond_stmt);
--
2.43.0
