yann@1: http://gcc.gnu.org/PR20973
yann@1: 
yann@1: "gcc 4 (about RC1) miscompiles khtml, in fact something in CSS, which basically 
yann@1: leads to all websites being misrendered.  I can't easily reduce the testcase, 
yann@1: but have applied the whole preprocessed source of css/cssstyleselector.ii. 
yann@1:  
yann@1: It is to be compiled with g++ -O2 -fPIC -march=i586 -mtune=i686 
yann@1: -fno-exceptions.  A more detailed analysis will follow, as we've found out 
yann@1: some things already."
yann@1: 
yann@1: ---
yann@1: 
yann@1: Subject: Bug 20973
yann@1: 
yann@1: CVSROOT:	/cvs/gcc
yann@1: Module name:	gcc
yann@1: Branch: 	gcc-4_0-branch
yann@1: Changes by:	matz@gcc.gnu.org	2005-04-22 17:30:21
yann@1: 
yann@1: Modified files:
yann@1: 	gcc            : ChangeLog reload.c 
yann@1: 
yann@1: Log message:
yann@1: 	PR middle-end/20973
yann@1: 	* reload.c (push_reload, find_dummy_reload): Check for uninitialized
yann@1: 	pseudos.
yann@1: 
yann@1: Patches:
yann@1: 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
yann@1: 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
yann@1: 
yann@1: ---
yann@1: 
yann@1: ===================================================================
yann@1: RCS file: /cvs/gcc/gcc/gcc/reload.c,v
yann@1: retrieving revision 1.268
yann@1: retrieving revision 1.268.2.1
yann@1: diff -u -r1.268 -r1.268.2.1
yann@1: --- gcc/gcc/reload.c	2005/02/24 22:06:06	1.268
yann@1: +++ gcc/gcc/reload.c	2005/04/22 17:30:15	1.268.2.1
yann@1: @@ -1520,7 +1520,7 @@
yann@1:       But if there is no spilling in this block, that is OK.
yann@1:       An explicitly used hard reg cannot be a spill reg.  */
yann@1:  
yann@1: -  if (rld[i].reg_rtx == 0 && in != 0)
yann@1: +  if (rld[i].reg_rtx == 0 && in != 0 && hard_regs_live_known)
yann@1:      {
yann@1:        rtx note;
yann@1:        int regno;
yann@1: @@ -1534,6 +1534,11 @@
yann@1:  	    && REG_P (XEXP (note, 0))
yann@1:  	    && (regno = REGNO (XEXP (note, 0))) < FIRST_PSEUDO_REGISTER
yann@1:  	    && reg_mentioned_p (XEXP (note, 0), in)
yann@1: +	    /* Check that we don't use a hardreg for an uninitialized
yann@1: +	       pseudo.  See also find_dummy_reload().  */
yann@1: +	    && (ORIGINAL_REGNO (XEXP (note, 0)) < FIRST_PSEUDO_REGISTER
yann@1: +		|| ! bitmap_bit_p (ENTRY_BLOCK_PTR->global_live_at_end,
yann@1: +				   ORIGINAL_REGNO (XEXP (note, 0))))
yann@1:  	    && ! refers_to_regno_for_reload_p (regno,
yann@1:  					       (regno
yann@1:  						+ hard_regno_nregs[regno]
yann@1: @@ -1997,7 +2002,17 @@
yann@1:  				is a subreg, and in that case, out
yann@1:  				has a real mode.  */
yann@1:  			     (GET_MODE (out) != VOIDmode
yann@1: -			      ? GET_MODE (out) : outmode)))
yann@1: +			      ? GET_MODE (out) : outmode))
yann@1: +        /* But only do all this if we can be sure, that this input
yann@1: +           operand doesn't correspond with an uninitialized pseudoreg.
yann@1: +           global can assign some hardreg to it, which is the same as
yann@1: +	   a different pseudo also currently live (as it can ignore the
yann@1: +	   conflict).  So we never must introduce writes to such hardregs,
yann@1: +	   as they would clobber the other live pseudo using the same.
yann@1: +	   See also PR20973.  */
yann@1: +      && (ORIGINAL_REGNO (in) < FIRST_PSEUDO_REGISTER
yann@1: +          || ! bitmap_bit_p (ENTRY_BLOCK_PTR->global_live_at_end,
yann@1: +			     ORIGINAL_REGNO (in))))
yann@1:      {
yann@1:        unsigned int regno = REGNO (in) + in_offset;
yann@1:        unsigned int nwords = hard_regno_nregs[regno][inmode];