Hi,
our kernel guys saw this problem when they used an asm goto to implement a
conditional where the then-block was empty. RTL ifcvt happily goes on and
removes the whole block and the jump instruction, even though it has
side-effects (as marked with the volatility). Patch below fixes it by
checking that it's really just a jump. Regstrapped on trunk. Okay for
trunk, 4.9, 4.8?
Ciao,
Michael.
PR rtl-optimization/61772
* ifcvt.c (dead_or_predicable): Check jump to be free of side
effects.
testsuite/
PR rtl-optimization/61772
* gcc.dg/torture/pr61772.c: New test.
Index: ifcvt.c
===================================================================
--- ifcvt.c (revision 212430)
+++ ifcvt.c (working copy)
@@ -4138,6 +4138,8 @@ dead_or_predicable (basic_block test_bb,
if (JUMP_P (end))
{
+ if (!onlyjump_p (end))
+ return FALSE;
if (head == end)
{
head = end = NULL_RTX;
Index: testsuite/gcc.dg/torture/pr61772.c
===================================================================
--- testsuite/gcc.dg/torture/pr61772.c (revision 0)
+++ testsuite/gcc.dg/torture/pr61772.c (working copy)
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-final { scan-assembler-times "XXX" 2 } } */
+
+static inline __attribute__((always_inline)) int dec_and_test (int *i)
+{
+ asm volatile goto ("XXX %0, %l[cc_label]"
+ : : "m" (*i) : "memory" : cc_label);
+ return 0;
+cc_label:
+ return 1;
+}
+extern int getit (int *);
+int f (int *i, int cond)
+{
+ if (cond) {
+ getit (0);
+ if (dec_and_test (i))
+ getit (i);
+ return 42;
+ }
+ if (dec_and_test (i))
+ (void)1;
+ return getit (i);
+}
