From: Neha Gowda <neha.gnu.gcc@gmail.com>
To: gcc-help@gcc.gnu.org
Subject: Should rand() return a RAND_MAX value for 32 bit target?
Date: Tue, 18 Sep 2018 12:22:00 -0000 [thread overview]
Message-ID: <CAODCPrOyjmXid=Rc_xagiud+t=b=u6DYGGBQs3z=AEAs+4JH6g@mail.gmail.com> (raw)
Hi,
I am trying to run the following testcase for Random Number Generator
function.
The testcase returns true when generated number is RAND_MAX and returns
false when its not generated.
Command :- gcc -m32 -O2 test.c
======================================================
#include <stdio.h>
#include <stdlib.h>
int main()
{
unsigned int i;
float f;
srand(0);
for (i = 0; i <= RAND_MAX; i++) {
f = rand();
if (f == RAND_MAX) {
printf("True\n");
return 0;
}
}
printf("False\n");
return 1;
}
======================================================
Tried them on the latest source and observed that the RAND_MAX is generated
when
the optimization is not enabled. When optimization is enabled for 32 bit
target RAND_MAX
is not being generated. However, 64 bit generates RAND_MAX with or without
optimization.
On further investigation, I found that the expand phase is optimizing the
following and hence
the RAND_MAX value is not being generated.
=========================================
Replacing Expressions
f_10 replace with --> f_10 = (float) _1;
=========================================
Can you please let me know if its the expected behavior or some bug?
Thanks,
Neha
next reply other threads:[~2018-09-18 12:22 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-18 12:22 Neha Gowda [this message]
2018-09-18 13:09 ` Xi Ruoyao
2018-09-18 13:17 ` Xi Ruoyao
2018-09-18 13:49 ` Jonathan Wakely
2018-09-18 13:46 ` Andrew Haley
2018-09-20 14:42 ` Vincent Lefevre
2018-09-20 15:05 ` Vincent Lefevre
2018-09-20 15:21 ` Liu Hao
2018-09-20 15:58 ` Vincent Lefevre
2018-09-20 16:12 ` Vincent Lefevre
2018-09-21 2:49 ` Liu Hao
2018-09-22 8:17 ` Vincent Lefevre
2018-09-22 10:08 ` Vincent Lefevre
2018-09-22 13:52 ` Liu Hao
2018-09-22 22:12 ` Vincent Lefevre
2018-09-20 15:46 ` Dennis Clarke
2018-09-20 16:16 ` Vincent Lefevre
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