At present, I suspect that qume's floating-point fmadd are not accurate enough.

from v8.

nice catch.

if it is a QEMU bug, the simulator team in PLCT would fix it.

you can report the issue to
https://github.com/isrc-cas/plct-qemu/issues
and mention Junqiang Wang or Weiwei Li. They would have a look for us.

from v8.

At present, I suspect that fmadd are not accurate enough.
I run the code on hifive unleashed:

int main() {
  float a = 67.56f, b = -1012.01f, c = 3456.13f;
  float acc = a * b + c;
  float exxpected = 67.56f * (-1012.01f) + 3456.13f;
  std::cout << (exxpected == acc) << " " << exxpected << " " << acc  << std::endl;
  asm(   
      "fmadd.s %0,%1,%2,%3\n"   
      :"=f"(acc)     
      :"f"(a),"f"(b),"f"(c)
      :
  );
  std::cout << (exxpected == acc) << " " << exxpected << " " << acc  << std::endl;
  return 0;
}

output:

1 -64915.3 -64915.3
0 -64915.3 -64915.3

compile command:
riscv64-unknown-linux-gnu-g++ ./test.cpp -o test

from v8.

#include <limits>
#include<iostream>
#include<string.h>

int main() {
  float a = 67.56f, b = -1012.01f, c = 3456.13f;
  float acc;
  float exxpected = 67.56f * (-1012.01f) + 3456.13f;
  asm(   
      "fmul.s %0,%1,%2\n"
      "fadd.s %0,%0,%3\n"   
      :"=f"(acc)     
      :"f"(a),"f"(b),"f"(c)
      :
  );
  std::cout << (exxpected == acc) << " " << exxpected << " " << acc  << std::endl;
 
  asm(   
      "fmadd.s %0,%1,%2,%3\n"   
      :"=f"(acc)     
      :"f"(a),"f"(b),"f"(c)
      :
  );
  std::cout << (exxpected == acc) << " " << exxpected << " " << acc  << std::endl;

  return 0;
}

from v8.

I run cctest/test-assembler-riscv64/RISCV_UTEST_swlwu

My code
https://github.com/luyahan/v8/blob/fix-macroassembler-test-macro_float_minmax_f64/test/cctest/test-assembler-riscv64.cc#L146

On qemu

Linux fedora-riscv 5.4.0-0.rc7.git0.1.1.riscv64.fc32.riscv64 #1 SMP Thu Nov 21 16:53:49 UTC 2019 riscv64 riscv64 riscv64 GNU/Linux

=== cctest/test-assembler-riscv64/RISCV_UTEST_swlwu ===
converted_res:int 2238380180 856af894
expected_res:int -2056587116 856af894
0
#
# Fatal error in ../../test/cctest/test-assembler-riscv64.cc, line 149
# Check failed: converted_res == expected_res (2238380180 vs. -2056587116).
#
#
#
#FailureMessage Object: 0x3fffc80ad8
==== C stack trace ===============================

    /root/cctest(v8::base::debug::StackTrace::StackTrace()+0x18) [0x2aba73f6ba]
    /root/cctest(+0x3c2e488) [0x2aba6aa488]
    /root/cctest(V8_Fatal(char const*, int, char const*, ...)+0xe2) [0x2aba4a4456]
    /root/cctest(+0x17b94c8) [0x2ab82354c8]
    /root/cctest(+0x17bfc54) [0x2ab823bc54]
    /root/cctest(CcTest::Run()+0x9e) [0x2ab7b61caa]
    /root/cctest(main+0x36e) [0x2ab7ae99de]
    /lib64/lp64d/libc.so.6(__libc_start_main+0xa0) [0x3fc12362a2]
    /root/cctest(_start+0x2c) [0x2ab7b5f1ec]
Command: cctest test-assembler-riscv64/RISCV_UTEST_swlwu --random-seed=1431394633 --nohard-abort --enable-slow-asserts --verify-heap --testing-d8-test-runner
[00:08|%   0|+   0|-   1]: Done
>>> 6579 base tests produced 1 (0%) non-filtered tests
>>> 1 tests ran

riscv64 toolchain

Using built-in specs.
COLLECT_GCC=riscv64-unknown-linux-gnu-g++
COLLECT_LTO_WRAPPER=/home/user/opt/riscv64/libexec/gcc/riscv64-unknown-linux-gnu/10.1.0/lto-wrapper
Target: riscv64-unknown-linux-gnu
Configured with: /home/user/qemu/plct-toolbox/riscv-gnu-toolchain/riscv-gcc/configure --target=riscv64-unknown-linux-gnu --prefix=/home/user/opt/riscv64 --with-sysroot=/home/user/opt/riscv64/sysroot --with-system-zlib --enable-shared --enable-tls --enable-languages=c,c++,fortran --disable-libmudflap --disable-libssp --disable-libquadmath --disable-libsanitizer --disable-nls --disable-bootstrap --src=.././riscv-gcc --disable-multilib --with-abi=lp64d --with-arch=rv64imafdc --with-tune=rocket 'CFLAGS_FOR_TARGET=-O2   -mcmodel=medlow' 'CXXFLAGS_FOR_TARGET=-O2   -mcmodel=medlow'
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.1.0 (GCC)

Output on x86 by clang or gcc7.5:

converted_res: -2056587116 856af894
expected_res: -2056587116 856af894
1

from v8.

I run cctest/test-assembler-riscv64/RISCV_UTEST_swlwu
My code
https://github.com/luyahan/v8/blob/fix-macroassembler-test-macro_float_minmax_f64/test/cctest/test-assembler-riscv64.cc#L146
On qemu
Linux fedora-riscv 5.4.0-0.rc7.git0.1.1.riscv64.fc32.riscv64 #1 SMP Thu Nov 21 16:53:49 UTC 2019 riscv64 riscv64 riscv64 GNU/Linux

=== cctest/test-assembler-riscv64/RISCV_UTEST_swlwu ===
converted_res:int 2238380180 856af894
expected_res:int -2056587116 856af894
0

Fatal error in ../../test/cctest/test-assembler-riscv64.cc, line 149

Check failed: converted_res == expected_res (2238380180 vs. -2056587116).

#FailureMessage Object: 0x3fffc80ad8
==== C stack trace ===============================

/root/cctest(v8::base::debug::StackTrace::StackTrace()+0x18) [0x2aba73f6ba]
/root/cctest(+0x3c2e488) [0x2aba6aa488]
/root/cctest(V8_Fatal(char const*, int, char const*, ...)+0xe2) [0x2aba4a4456]
/root/cctest(+0x17b94c8) [0x2ab82354c8]
/root/cctest(+0x17bfc54) [0x2ab823bc54]
/root/cctest(CcTest::Run()+0x9e) [0x2ab7b61caa]
/root/cctest(main+0x36e) [0x2ab7ae99de]
/lib64/lp64d/libc.so.6(__libc_start_main+0xa0) [0x3fc12362a2]
/root/cctest(_start+0x2c) [0x2ab7b5f1ec]

Command: cctest test-assembler-riscv64/RISCV_UTEST_swlwu --random-seed=1431394633 --nohard-abort --enable-slow-asserts --verify-heap --testing-d8-test-runner
[00:08|% 0|+ 0|- 1]: Done

6579 base tests produced 1 (0%) non-filtered tests
1 tests ran

riscv64 toolchain
Using built-in specs.
COLLECT_GCC=riscv64-unknown-linux-gnu-g++
COLLECT_LTO_WRAPPER=/home/user/opt/riscv64/libexec/gcc/riscv64-unknown-linux-gnu/10.1.0/lto-wrapper
Target: riscv64-unknown-linux-gnu
Configured with: /home/user/qemu/plct-toolbox/riscv-gnu-toolchain/riscv-gcc/configure --target=riscv64-unknown-linux-gnu --prefix=/home/user/opt/riscv64 --with-sysroot=/home/user/opt/riscv64/sysroot --with-system-zlib --enable-shared --enable-tls --enable-languages=c,c++,fortran --disable-libmudflap --disable-libssp --disable-libquadmath --disable-libsanitizer --disable-nls --disable-bootstrap --src=.././riscv-gcc --disable-multilib --with-abi=lp64d --with-arch=rv64imafdc --with-tune=rocket 'CFLAGS_FOR_TARGET=-O2 -mcmodel=medlow' 'CXXFLAGS_FOR_TARGET=-O2 -mcmodel=medlow'
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.1.0 (GCC)

Output on x86 by clang or gcc7.5:
converted_res: -2056587116 856af894
expected_res: -2056587116 856af894
1

On qemu
./cctest test-assembler-riscv64/RISCV_UTEST_swlwu --random-seed=-842269837 --nohard-abort --enable-slow-asserts --verify-heap --testing-d8-test-runner
report error.

b ValidateResult<int, int> ()
Thread 1 "cctest" hit Breakpoint 4, ValidateResult<int, int> ()
(gdb) info r a0
a0 0x856af894 2238380180
(gdb) info r a1
a1 0xffffffff856af894 -2056587116
(gdb)
may be the value 0x856af894 is zero extend in a0, and sign extend in a1？

from v8.

This issue had be fixed by #38 .

from v8.