diff mbox

Fix PR61772: ifcvt removing asm volatile gotos

Message ID alpine.LNX.2.00.1407111425200.31863@wotan.suse.de
State New
Headers show

Commit Message

Michael Matz July 11, 2014, 12:34 p.m. UTC 
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.

Comments

Steven Bosscher July 11, 2014, 2:36 p.m. UTC | #1 
On Fri, Jul 11, 2014 at 2:34 PM, Michael Matz wrote:
>         PR rtl-optimization/61772
>         * ifcvt.c (dead_or_predicable): Check jump to be free of side
>         effects.

This is OK.

Ciao!
Steven
diff mbox

Patch

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);
+}