[PATCH] Fix ICE with useless VALUE in ix86_pic_register_p (PR target/41762)

[PATCH] Fix ICE with useless VALUE in ix86_pic_register_p (PR target/41762)

[Jakub Jelinek]

Hi!

Roughly a year ago ix86_pic_register_p was added to do a cselib
lookup to find more occurences of pic register when deligitimizing
addresses on i386.  Unfortunately, as the testcase below on 4.4 branch
shows, it can ICE when seeing a VALUE already discarded by
remove_useless_value.  As the i386 backend uses it always, without checking
what kind of pass uses cselib and whether it preserves VALUEs or not, we
IMHO need to be as careful as e.g. aliasing code is.  get_addr in alias.c
also passes through VALUE with NULL CSELIB_VAL_PTR (i.e. VALUE discarded as
useless), instead of dereferencing it unconditionally.
VALUE rtxs are preserved until cselib_finish, which is usually end of pass,
but the associated cselib structures are freed earlier if deemed useless
and not preserved.

Bootstrapped/regtested on x86_64-linux (with r152315 reverted) and
i686-linux, ok for trunk/4.4?

2009-10-23  Jakub Jelinek  <jakub@redhat.com>

	PR target/41762
	* config/i386/i386.c (ix86_pic_register_p): Don't call
	rtx_equal_for_cselib_p for VALUEs discarded as useless.

	* gcc.dg/pr41762.c: New test.

--- gcc/config/i386/i386.c.jj	2009-09-29 17:58:03.000000000 +0200
+++ gcc/config/i386/i386.c	2009-10-23 19:08:19.000000000 +0200
@@ -10379,7 +10379,7 @@ i386_output_dwarf_dtprel (FILE *file, in
 static bool
 ix86_pic_register_p (rtx x)
 {
-  if (GET_CODE (x) == VALUE)
+  if (GET_CODE (x) == VALUE && CSELIB_VAL_PTR (x))
     return (pic_offset_table_rtx
 	    && rtx_equal_for_cselib_p (x, pic_offset_table_rtx));
   else
--- gcc/testsuite/gcc.dg/pr41762.c.jj	2009-10-23 19:15:42.000000000 +0200
+++ gcc/testsuite/gcc.dg/pr41762.c	2009-10-23 19:14:35.000000000 +0200
@@ -0,0 +1,31 @@
+/* PR target/41762 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftracer -fsched2-use-superblocks" } */
+/* { dg-options "-O2 -ftracer -fsched2-use-superblocks -fpic" { target fpic } } */
+
+extern __SIZE_TYPE__ strlen (const char *);
+extern int f1 (void *);
+extern char *f2 (void);
+extern void f3 (int, int);
+static char *a;
+char *b, *c, *d, *e;
+
+void
+foo (void)
+{
+  int f, g, h;
+  f = (a ? strlen (a) : strlen ("abcde"));
+  f += (b ? strlen (b) : 0);
+  f += (c ? strlen (c) : 0);
+  f += (d ? strlen (d) : 0);
+  f += (e ? strlen (e) : 0);
+  h = f1 (strlen);
+  g = strlen (a);
+  f3 (g, f);
+}
+
+void
+bar (void)
+{
+  a = f2 ();
+}

	Jakub

Re: [PATCH] Fix ICE with useless VALUE in ix86_pic_register_p (PR target/41762)

[Ian Lance Taylor]

Jakub Jelinek <jakub@redhat.com> writes:

> 2009-10-23  Jakub Jelinek  <jakub@redhat.com>
>
> 	PR target/41762
> 	* config/i386/i386.c (ix86_pic_register_p): Don't call
> 	rtx_equal_for_cselib_p for VALUEs discarded as useless.
>
> 	* gcc.dg/pr41762.c: New test.

This is OK.

Thanks.

Ian