Re: Regression with recent change

[Aldy Hernandez via Gcc-patches]

On 9/14/21 4:13 PM, Michael Matz wrote:
Hello,

On Mon, 13 Sep 2021, Aldy Hernandez via Gcc-patches wrote:

The testcase still tests what it's supposed to test with ...

typedef unsigned short uint16_t;

uint16_t a, b;

int *j_global;
uint16_t f(void)
{
    int c, **p;
    short d = 2, e = 4;


... "c = a;" added here (i.e. it still hangs before the pr55107 change).

    for (;; b++)
      {
        int *j = j_global, k = 0;

        for (; *j; j++)
       {
         for(; c; c++)
           for(; k < 1; k++)
             {
               short *f = &d;

               if(b)
                 return *f;
             }
       }

        if(!c)
       d *= e;

        a = d;
        if ((a ? b = 0 : (**p ? : 1) != (d != 1 ? 1 : (b = 0))) != ((k ? a
: 0)
         < (a * (c = k))))
       **p = 0;
      }
}


Thanks for getting rid of the noise here.

I've simplified the above to show what's going on in the warning on
nds32-elf:

int george, *global;
int stuff(), readme();

int
f (void)
{
    int store;

    for (;;)
      {
        int k = 0;

        while (global)
         {
           for (; store; ++store)

Yeah, that seems a correct warning, your 'store' (the 'c' in the original
testcase) is really used uninitialized (when 'global' aka '*j_global' is
non-zero).  Sorry for not noticing earlier, I was only getting rid of
warnings, not carefully looking at the testcase itself.  I think with
above initialization of 'c' it's conforming, and still a correct test for
the original bug.

This is good news.  So far, every single warning/problem that has 
surfaced with the backward threader rewrite has been a latent bug 
elsewhere (or a bad test) :-).

Would you mind checking in your changes to the testcase?

Thanks.
Aldy