Re: optimization/9279: [3.2 regression] [Sparc] combine bug

["Christian Ehrhardt" <ehrhardt@mathematik.uni-ulm.de>]

The following reply was made to PR optimization/9279; it has been noted by GNATS.

From: "Christian Ehrhardt" <ehrhardt@mathematik.uni-ulm.de>
To: gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org, frank@g-n-u.de,
  nobody@gcc.gnu.org, gcc-prs@gcc.gnu.org, doko@debian.org
Cc:  
Subject: Re: optimization/9279: [3.2 regression] [Sparc] combine bug
Date: Fri, 24 Jan 2003 11:57:26 +0100

 Hi,
 
 here's an even simpler example:
 
 
 int x = 0;
 char c, * p = &c, a = -1;
 int main ()
 {
 	if ((x?0:(unsigned char)((*p) = a)) == -1)
 		return 0;
 	return 1;
 }
 
 The exitcode of this program should always be 1 but it is zero if
 compiled with -O2.
 
 The problem is that these two insns
 
 (insn 24 23 25 (set (reg:SI 117)
         (zero_extend:SI (reg:QI 116))) 126 {*zero_extendqisi2_insn} (nil)
     (expr_list:REG_DEAD (reg:QI 116)
         (nil)))
 
 (insn 25 24 26 (set (reg:CC 100 %icc)
         (compare:CC (reg:SI 117)
             (const_int -1 [0xffffffffffffffff]))) 0 {*cmpsi_insn} (insn_list 24 (nil))
     (expr_list:REG_DEAD (reg:SI 117)
         (nil)))
 
 are combined into one like this:
 
 (note 24 23 25 NOTE_INSN_DELETED)
 
 (insn 25 24 26 (set (reg:CC 100 %icc)
         (compare:CC (subreg:SI (reg:QI 116) 0)
             (const_int 255 [0xff]))) 0 {*cmpsi_insn} (nil)
     (expr_list:REG_DEAD (reg:QI 116)
         (nil)))
 
    regards  Christian