1 http://gcc.gnu.org/PR20973
3 "gcc 4 (about RC1) miscompiles khtml, in fact something in CSS, which basically
4 leads to all websites being misrendered. I can't easily reduce the testcase,
5 but have applied the whole preprocessed source of css/cssstyleselector.ii.
7 It is to be compiled with g++ -O2 -fPIC -march=i586 -mtune=i686
8 -fno-exceptions. A more detailed analysis will follow, as we've found out
17 Branch: gcc-4_0-branch
18 Changes by: matz@gcc.gnu.org 2005-04-22 17:30:21
21 gcc : ChangeLog reload.c
25 * reload.c (push_reload, find_dummy_reload): Check for uninitialized
29 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=2.7592.2.177&r2=2.7592.2.178
30 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/reload.c.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=1.268&r2=1.268.2.1
34 ===================================================================
35 RCS file: /cvs/gcc/gcc/gcc/reload.c,v
36 retrieving revision 1.268
37 retrieving revision 1.268.2.1
38 diff -u -r1.268 -r1.268.2.1
39 --- gcc/gcc/reload.c 2005/02/24 22:06:06 1.268
40 +++ gcc/gcc/reload.c 2005/04/22 17:30:15 1.268.2.1
42 But if there is no spilling in this block, that is OK.
43 An explicitly used hard reg cannot be a spill reg. */
45 - if (rld[i].reg_rtx == 0 && in != 0)
46 + if (rld[i].reg_rtx == 0 && in != 0 && hard_regs_live_known)
50 @@ -1534,6 +1534,11 @@
51 && REG_P (XEXP (note, 0))
52 && (regno = REGNO (XEXP (note, 0))) < FIRST_PSEUDO_REGISTER
53 && reg_mentioned_p (XEXP (note, 0), in)
54 + /* Check that we don't use a hardreg for an uninitialized
55 + pseudo. See also find_dummy_reload(). */
56 + && (ORIGINAL_REGNO (XEXP (note, 0)) < FIRST_PSEUDO_REGISTER
57 + || ! bitmap_bit_p (ENTRY_BLOCK_PTR->global_live_at_end,
58 + ORIGINAL_REGNO (XEXP (note, 0))))
59 && ! refers_to_regno_for_reload_p (regno,
61 + hard_regno_nregs[regno]
62 @@ -1997,7 +2002,17 @@
63 is a subreg, and in that case, out
65 (GET_MODE (out) != VOIDmode
66 - ? GET_MODE (out) : outmode)))
67 + ? GET_MODE (out) : outmode))
68 + /* But only do all this if we can be sure, that this input
69 + operand doesn't correspond with an uninitialized pseudoreg.
70 + global can assign some hardreg to it, which is the same as
71 + a different pseudo also currently live (as it can ignore the
72 + conflict). So we never must introduce writes to such hardregs,
73 + as they would clobber the other live pseudo using the same.
74 + See also PR20973. */
75 + && (ORIGINAL_REGNO (in) < FIRST_PSEUDO_REGISTER
76 + || ! bitmap_bit_p (ENTRY_BLOCK_PTR->global_live_at_end,
77 + ORIGINAL_REGNO (in))))
79 unsigned int regno = REGNO (in) + in_offset;
80 unsigned int nwords = hard_regno_nregs[regno][inmode];