[Bug tree-optimization/87546] [9 Regression] Gcc miscompiles at -O3 on valid code

[graham.stott77 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87546

--- Comment #3 from graham.stott77 at gmail dot com ---
'b' is never assigned a value, so surely it's undefined

-------- Original message --------
From: helloqirun at gmail dot com <gcc-bugzi...@gcc.gnu.org> 
Date: 08/10/2018  04:51  (GMT+00:00) 
To: gcc-bugs@gcc.gnu.org 
Subject: [Bug tree-optimization/87546] New: Gcc miscompiles at -O3 on valid
code 

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87546

            Bug ID: 87546
           Summary: Gcc miscompiles at -O3 on valid code
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: helloqirun at gmail dot com
  Target Milestone: ---

It should be a very recent regression.


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/home/absozero/trunk/root-gcc/libexec/gcc/x86_64-pc-linux-gnu/9.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/home/absozero/trunk/root-gcc
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 9.0.0 20181007 (experimental) [trunk revision 264906] (GCC)


$ gcc-trunk abc.c ; ./a.out
-37
$ gcc-trunk -O3 abc.c ; ./a.out
219


$ cat abc.c
int printf(const char *, ...);
int a;
long b, f;
char c, g;
short d = 219;
int e[7];
int main() {
  for (; c <= 6; c++) {
    g = d < 0 ? d : d >> a;
    f = g + b;
    e[c] = f;
  }
  printf("%d\n", e[1]);
}