Bootstrapped and regtested on x86_64-redhat-linux, ppc64le-redhat-linux
and s390x-redhat-linux.
Linux Kernel (specifically, drivers/leds/trigger/ledtrig-cpu.c) build
with GCC 10 fails on s390 with "impossible constraint".
The problem is that jump threading makes __builtin_constant_p lie when
an expression in question appears to be a constant on a threading path.
Fix by disallowing __builtin_constant_p on threading paths.
gcc/ChangeLog:
2020-06-03 Ilya Leoshkevich <i...@linux.ibm.com>
* tree-ssa-threadbackward.c (thread_jumps::profitable_jump_thread_path):
Do not allow __builtin_constant_p on a threading path.
gcc/testsuite/ChangeLog:
2020-06-03 Ilya Leoshkevich <i...@linux.ibm.com>
* gcc.target/s390/builtin-constant-p-threading.c: New test.
---
.../s390/builtin-constant-p-threading.c | 46 +++++++++++++++++++
gcc/tree-ssa-threadbackward.c | 7 ++-
2 files changed, 52 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.target/s390/builtin-constant-p-threading.c
diff --git a/gcc/testsuite/gcc.target/s390/builtin-constant-p-threading.c
b/gcc/testsuite/gcc.target/s390/builtin-constant-p-threading.c
new file mode 100644
index 00000000000..5f0acdce0b0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/builtin-constant-p-threading.c
@@ -0,0 +1,46 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=z196 -mzarch" } */
+
+typedef struct
+{
+ int counter;
+} atomic_t;
+
+static inline __attribute__ ((__gnu_inline__)) int
+__atomic_add (int val, int *ptr)
+{
+ int old;
+ asm volatile("laa %[old],%[val],%[ptr]\n"
+ : [old] "=d" (old), [ptr] "+Q"(*ptr)
+ : [val] "d" (val)
+ : "cc", "memory");
+ return old;
+}
+
+static inline __attribute__ ((__gnu_inline__)) void
+__atomic_add_const (int val, int *ptr)
+{
+ asm volatile("asi %[ptr],%[val]\n"
+ : [ptr] "+Q" (*ptr)
+ : [val] "i" (val)
+ : "cc", "memory");
+}
+
+static inline __attribute__ ((__gnu_inline__)) void
+atomic_add (int i, atomic_t *v)
+{
+ if (__builtin_constant_p (i) && (i > -129) && (i < 128))
+ {
+ __atomic_add_const (i, &v->counter);
+ return;
+ }
+ __atomic_add (i, &v->counter);
+}
+
+static atomic_t num_active_cpus = { (0) };
+
+void
+ledtrig_cpu (_Bool is_active)
+{
+ atomic_add (is_active ? 1 : -1, &num_active_cpus);
+}
diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
index 327628f1662..668932f6d85 100644
--- a/gcc/tree-ssa-threadbackward.c
+++ b/gcc/tree-ssa-threadbackward.c
@@ -259,8 +259,13 @@ thread_jumps::profitable_jump_thread_path (basic_block
bbi, tree name,
!gsi_end_p (gsi);
gsi_next_nondebug (&gsi))
{
+ /* Do not allow OpenACC loop markers and __builtin_constant_p on
+ a threading path. The latter is disallowed, because an
+ expression being constant on a threading path does not mean it
+ can be considered constant in the entire function. */
gimple *stmt = gsi_stmt (gsi);
- if (gimple_call_internal_p (stmt, IFN_UNIQUE))
+ if (gimple_call_internal_p (stmt, IFN_UNIQUE)
+ || gimple_call_builtin_p (stmt, BUILT_IN_CONSTANT_P))
{
m_path.pop ();
return NULL;
--
2.25.4
