[Qemu-devel] [Bug 1821444] Re: qemu-ppc (user) incorrectly translates float32 arithmetics
Alternatively 'uint64_t helper_todouble(uint32_t)' could be implemented via
include/fpu/softfloat.h:float64 float32_to_float64(float32, float_status
*status);
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https://bugs.launchpad.net/bugs/1821444
Title:
qemu-ppc (user) incorrectly translates float32 arithmetics
Status in QEMU:
New
Bug description:
I'm using qemu-3.1.0 (Gentoo).
When I was running regression test suite via qemu-ppc for GHC I
noticed a few uint32_t<->float32 failures I did not expect to
encounter.
Here is an example
$ cat a.c
#include
#include
int main() {
volatile uint32_t i = 1;
printf("0x1 = %e\n", *(volatile float*));
}
$ powerpc-unknown-linux-gnu-gcc -O2 a.c -Wall -o a -fno-strict-aliasing
-fno-stack-protector -static && ./a
0x1 = 2.802597e-45
$ scp a timberdoodle.ppc64.dev.gentoo.org:~/
a
100% 826KB 102.0KB/s 00:08
$ ssh timberdoodle.ppc64.dev.gentoo.org ./a
0x1 = 1.401298e-45
$ qemu-ppc ./a
0x1 = 2.802597e-45
Looks like off-by-one bit somewhere. I'm not sure if it's FPU
instruction or some internals of printf() that are emulated
incorrectly.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1821444/+subscriptions
[Qemu-devel] [Bug 1821444] Re: qemu-ppc (user) incorrectly translates float32 arithmetics
Attaching the patch and sending for review as:
https://lists.gnu.org/archive/html/qemu-devel/2019-03/msg06562.html
** Patch added: "patch to fix denormals"
https://bugs.launchpad.net/qemu/+bug/1821444/+attachment/5248915/+files/0001-powerpc-fix-denorm-float-double-conversion.patch
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https://bugs.launchpad.net/bugs/1821444
Title:
qemu-ppc (user) incorrectly translates float32 arithmetics
Status in QEMU:
New
Bug description:
I'm using qemu-3.1.0 (Gentoo).
When I was running regression test suite via qemu-ppc for GHC I
noticed a few uint32_t<->float32 failures I did not expect to
encounter.
Here is an example
$ cat a.c
#include
#include
int main() {
volatile uint32_t i = 1;
printf("0x1 = %e\n", *(volatile float*));
}
$ powerpc-unknown-linux-gnu-gcc -O2 a.c -Wall -o a -fno-strict-aliasing
-fno-stack-protector -static && ./a
0x1 = 2.802597e-45
$ scp a timberdoodle.ppc64.dev.gentoo.org:~/
a
100% 826KB 102.0KB/s 00:08
$ ssh timberdoodle.ppc64.dev.gentoo.org ./a
0x1 = 1.401298e-45
$ qemu-ppc ./a
0x1 = 2.802597e-45
Looks like off-by-one bit somewhere. I'm not sure if it's FPU
instruction or some internals of printf() that are emulated
incorrectly.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1821444/+subscriptions
[Qemu-devel] [Bug 1821444] Re: qemu-ppc (user) incorrectly translates float32 arithmetics
A bit more investigation:
It looks like the bug happens in float->double conversion direction.
$ cat a.c
#include
#include
int main() {
volatile uint32_t i = 1;
volatile float f;
volatile double d;
*(volatile uint32_t*) = i;
d = f;
printf("d = %#llx (expect 0x36a0)\n", *(volatile uint64_t*));
}
$ powerpc-unknown-linux-gnu-gcc -O2 a.c -Wall -o a -fno-strict-aliasing
-fno-stack-protector -static && qemu-ppc ./a
d = 0x36b8 (expect 0x36a0)
1400 :
1404: 39 20 00 01 li r9,1
...
1434: 91 21 00 10 stw r9,16(r1)
...
143c: c0 01 00 10 lfs f0,16(r1)
1440: d8 01 00 08 stfdf0,8(r1)
...
1448: 80 a1 00 08 lwz r5,8(r1)
144c: 80 c1 00 0c lwz r6,12(r1)
...
1454: 48 02 01 ad bl 10020600 <___printf_chk>
This is just lfs/stfd conversion. qemu does translates that pair if
instructions into:
$ ppc-linux-user/qemu-ppc -d in_asm,out_asm,op,op_opt /tmp/b/a
...
IN: main
...
0x143c: c0010010 lfs f0, 0x10(r1)
0x1440: d8010008 stfd f0, 8(r1)
...
OP:
143c
movi_i32 tmp1,$0x10
add_i32 tmp0,r1,tmp1
qemu_ld_i32 tmp1,tmp0,beul,2
call todouble,$0x5,$1,tmp2,tmp1
st_i64 tmp2,env,$0x9198
'todouble' must be a 'uint64_t helper_todouble(uint32_t arg=0x1)' from:
https://github.com/qemu/qemu/blob/master/target/ppc/fpu_helper.c#L55
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1821444
Title:
qemu-ppc (user) incorrectly translates float32 arithmetics
Status in QEMU:
New
Bug description:
I'm using qemu-3.1.0 (Gentoo).
When I was running regression test suite via qemu-ppc for GHC I
noticed a few uint32_t<->float32 failures I did not expect to
encounter.
Here is an example
$ cat a.c
#include
#include
int main() {
volatile uint32_t i = 1;
printf("0x1 = %e\n", *(volatile float*));
}
$ powerpc-unknown-linux-gnu-gcc -O2 a.c -Wall -o a -fno-strict-aliasing
-fno-stack-protector -static && ./a
0x1 = 2.802597e-45
$ scp a timberdoodle.ppc64.dev.gentoo.org:~/
a
100% 826KB 102.0KB/s 00:08
$ ssh timberdoodle.ppc64.dev.gentoo.org ./a
0x1 = 1.401298e-45
$ qemu-ppc ./a
0x1 = 2.802597e-45
Looks like off-by-one bit somewhere. I'm not sure if it's FPU
instruction or some internals of printf() that are emulated
incorrectly.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1821444/+subscriptions
[Qemu-devel] [Bug 1821444] Re: qemu-ppc (user) incorrectly translates float32 arithmetics
Shorter example without relying on printf() implementation. Looks like
uint32_t<->float<->double transitions are enough.
$ cat a.c
#include
#include
int main() {
volatile uint32_t i = 1;
volatile float f;
volatile double d;
*(volatile uint32_t*) = i;
d = f; f = d; // double conversion
i = *(volatile uint32_t*)
printf("0x1 = %x\n", i);
}
$ powerpc-unknown-linux-gnu-gcc -O2 a.c -Wall -o a -fno-strict-aliasing
-fno-stack-protector -static && qemu-ppc ./a
0x1 = 2
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1821444
Title:
qemu-ppc (user) incorrectly translates float32 arithmetics
Status in QEMU:
New
Bug description:
I'm using qemu-3.1.0 (Gentoo).
When I was running regression test suite via qemu-ppc for GHC I
noticed a few uint32_t<->float32 failures I did not expect to
encounter.
Here is an example
$ cat a.c
#include
#include
int main() {
volatile uint32_t i = 1;
printf("0x1 = %e\n", *(volatile float*));
}
$ powerpc-unknown-linux-gnu-gcc -O2 a.c -Wall -o a -fno-strict-aliasing
-fno-stack-protector -static && ./a
0x1 = 2.802597e-45
$ scp a timberdoodle.ppc64.dev.gentoo.org:~/
a
100% 826KB 102.0KB/s 00:08
$ ssh timberdoodle.ppc64.dev.gentoo.org ./a
0x1 = 1.401298e-45
$ qemu-ppc ./a
0x1 = 2.802597e-45
Looks like off-by-one bit somewhere. I'm not sure if it's FPU
instruction or some internals of printf() that are emulated
incorrectly.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1821444/+subscriptions
[Qemu-devel] [Bug 1821444] Re: qemu-ppc (user) incorrectly translates float32 arithmetics
My native system is x86_64-pc-linux-gnu with a few binfmt_misc handlers wired. Checking other targets I have locally I get the following: affected targets: - powerpc - powerpc64 - powerpc64le unaffected targets: - arm - arm64 - hppa - sparc probably unaffected: - alpha (maybe it's ok as alpha is not quite an IEEE754 platform) Raw log: $ for gcc in /usr/bin/*-gcc; do rm -f a; $gcc -O2 a.c -Wall -o a -fno- strict-aliasing -fno-stack-protector 2>/dev/null && ./a 2>/dev/null && echo -n "$gcc: " && file a; done | sort 0x1 = 1.401298e-45 : /usr/bin/aarch64-unknown-linux-gnu-gcc: a: ELF 64-bit LSB pie executable, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64.so.1, for GNU/Linux 3.7.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/aarch64_be-unknown-linux-gnu-gcc: a: ELF 64-bit MSB pie executable, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64_be.so.1, for GNU/Linux 3.7.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/afl-gcc: a: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, with debug_info, not stripped 0x1 = 1.401298e-45 : /usr/bin/armv6j-unknown-linux-gnueabihf-gcc: a: ELF 32-bit LSB pie executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, for GNU/Linux 3.2.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/armv7a-unknown-linux-gnueabihf-gcc: a: ELF 32-bit LSB pie executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, for GNU/Linux 3.2.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/hppa-unknown-linux-gnu-gcc: a: ELF 32-bit MSB pie executable, PA-RISC, 1.1 version 1 (GNU/Linux), dynamically linked, interpreter /lib/ld.so.1, for GNU/Linux 3.2.0, with debug_info, not stripped 0x1 = 1.401298e-45 : /usr/bin/hppa2.0-unknown-linux-gnu-gcc: a: ELF 32-bit MSB pie executable, PA-RISC, 1.1 version 1 (GNU/Linux), dynamically linked, interpreter /lib/ld.so.1, for GNU/Linux 3.2.0, with debug_info, not stripped 0x1 = 1.401298e-45 : /usr/bin/m68k-unknown-linux-gnu-gcc: a: ELF 32-bit MSB pie executable, Motorola m68k, 68020, version 1 (SYSV), dynamically linked, interpreter /lib/ld.so.1, for GNU/Linux 3.2.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/mips64-unknown-linux-gnuabin64-gcc: a: ELF 64-bit MSB pie executable, MIPS, MIPS-III version 1 (SYSV), dynamically linked, interpreter /lib64/ld.so.1, for GNU/Linux 3.2.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/riscv64-unknown-linux-gnu-gcc: a: ELF 64-bit LSB pie executable, UCB RISC-V, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-riscv64-lp64d.so.1, for GNU/Linux 4.15.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/s390x-unknown-linux-gnu-gcc: a: ELF 64-bit MSB pie executable, IBM S/390, version 1 (SYSV), dynamically linked, interpreter /lib/ld64.so.1, for GNU/Linux 3.2.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/sparc-unknown-linux-gnu-gcc: a: ELF 32-bit MSB pie executable, SPARC32PLUS, V8+ Required, total store ordering, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.2, for GNU/Linux 3.2.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/x86_64-HEAD-linux-gnu-gcc: a: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/x86_64-UNREG-linux-gnu-gcc: a: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, not stripped 0x1 = 1.401298e-45 : /usr/bin/x86_64-pc-linux-gnu-gcc: a: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, with debug_info, not stripped 0x1 = 2.652494e-315 : /usr/bin/alpha-unknown-linux-gnu-gcc: a: ELF 64-bit LSB pie executable, Alpha (unofficial), version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.2, for GNU/Linux 3.2.0, not stripped 0x1 = 2.802597e-45 : /usr/bin/powerpc-unknown-linux-gnu-gcc: a: ELF 32-bit MSB pie executable, PowerPC or cisco 4500, version 1 (SYSV), dynamically linked, interpreter /lib/ld.so.1, for GNU/Linux 3.2.0, not stripped 0x1 = 2.802597e-45 : /usr/bin/powerpc64-unknown-linux-gnu-gcc: a: ELF 64-bit MSB pie executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), dynamically linked, interpreter /lib64/ld64.so.1, for GNU/Linux 3.2.0, not stripped 0x1 = 2.802597e-45 : /usr/bin/powerpc64le-unknown-linux-gnu-gcc: a: ELF 64-bit LSB pie executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), dynamically linked, interpreter /lib64/ld64.so.2, for GNU/Linux 3.10.0, not stripped -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1821444 Title: qemu-ppc (user) incorrectly translates float32 arithmetics Status in
