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From: "jovan.dmitrovic at syrmia dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug other/109435] New: [MIPS64R6] Typedef struct alignment returns
 incorrect results
Date: Thu, 06 Apr 2023 14:04:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109435

            Bug ID: 109435
           Summary: [MIPS64R6] Typedef struct alignment returns incorrect
                    results
           Product: gcc
           Version: 10.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jovan.dmitrovic at syrmia dot com
  Target Milestone: ---

Consider the following testcase:


#include<stdio.h>

typedef struct uint8 {
  unsigned v[8];
} uint8 __attribute__ ((aligned(128)));

unsigned callee(int x, uint8 a) {
    return a.v[0];
}

uint8 identity(uint8 in) {
    return in;
}

int main() {
    uint8 vec =3D {1, 2, 3, 4, 5, 6, 7, 8};
    printf("res1: %d\n", callee(99, identity(vec)));
    uint8 temp =3D identity(vec);
    printf("res2: %d\n", callee(99, temp));
}


When this code is compiled for MIPS64 R6, output is as follows:

res1: 3
res2: 1

However, when aligned attribute is removed from the testcase, res1 and res2
become 1,
which are values that were expected in the first place.=20
Furthermore, this bug is reproducible only if there is a unused argument x =
in
function callee. Adding more arguments or switching their places also produ=
ces
expected values. Type of x doesn't seem to impact the result.=