[Bug middle-end/86554] New: Incorrect code generation with signed/unsigned comparison

[anton at samba dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86554

            Bug ID: 86554
           Summary: Incorrect code generation with signed/unsigned
                    comparison
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anton at samba dot org
  Target Milestone: ---

The test case below fails on both ppc64le and x86_64 when built with -O2, I
see:

ret is 1017
ret is < 1

Looking at the code, the < 1 comparison is removed completely.

--


#include <stdio.h>
#include <stdint.h>

struct foo
{
        uint32_t x;
};
typedef struct foo foo;

static inline int zot(foo *f)
{
        int ret;

        if (f->x > 0x7FFFFFFF)
                ret = (int)(f->x - 0x7FFFFFFF);
        else
                ret = (int)f->x - 0x7FFFFFFF;
        return ret;
}

void bar(foo *f)
{
        int ret = zot(f);

        printf("ret is %d\n", ret);
        if (ret < 1)
                printf("ret is < 1\n");
}

int main(void)
{
        foo f;
        f.x = 0x800003f8;

        bar(&f);
}