While running the GCC test suite against 4.0.0-rc0, Kito found a
regression introduced by the decodetree conversion that caused divuw and
remuw to sign-extend their inputs. The ISA manual says they are
supposed to be zero extended:
DIVW and DIVUW instructions are only valid for RV64, and divide the
lower 32 bits of rs1 by the lower 32 bits of rs2, treating them as
signed and unsigned integers respectively, placing the 32-bit
quotient in rd, sign-extended to 64 bits. REMW and REMUW
instructions are only valid for RV64, and provide the corresponding
signed and unsigned remainder operations respectively. Both REMW
and REMUW always sign-extend the 32-bit result to 64 bits, including
on a divide by zero.
Here's Kito's reduced test case from the GCC test suite
unsigned calc_mp(unsigned mod)
{
unsigned a,b,c;
c=-1;
a=c/mod;
b=0-a*mod;
if (b > mod) { a += 1; b-=mod; }
return b;
}
int main(int argc, char *argv[])
{
unsigned x = 1234;
unsigned y = calc_mp(x);
if ((sizeof (y) == 4 && y != 680)
|| (sizeof (y) == 2 && y != 134))
abort ();
exit (0);
}
I haven't done any other testing on this, but it does fix the test case.
Backports commit f17e02cd3731bdfe2942d1d0b2a92f26da02408c from qemu
during the refactor to decodetree we removed the manual decoding that is
necessary for c.jal/c.addiw and removed the translation of c.flw/c.ld
and c.fsw/c.sd. This reintroduces the manual parsing and the
omited implementation.
Backports commit f330433b3633647b047cfa418c2ca4d18fda69c7 from qemu
manual decoding in gen_arith() is not necessary with decodetree. For now
the function is called trans_arith as the original gen_arith still
exists. The former will be renamed to gen_arith as soon as the old
gen_arith can be removed.
Backports commit f2ab1728675772cd475a33f4df3d2f68a22c188f from qemu
gen_arith_imm() does a lot of decoding manually, which was hard to read
in case of the shift instructions and is not necessary anymore with
decodetree.
Backports commit 7a50d3e2ae7f13b24fe55990ea0b8ddcbbb43130 from qemu
With decodetree we don't need to convert RISC-V opcodes into to MemOps
as the old gen_store() did.
Backports commit bce8a342a1f0919479d18ec812b100136daa746b from qemu
With decodetree we don't need to convert RISC-V opcodes into to MemOps
as the old gen_load() did.
Backports commit 98898b20e9cca462843c22ad952c216ffd57d654 from qemu
We now utilizes argument-sets of decodetree such that no manual
decoding is necessary.
Backports commit 090cc2c898a04e42350eabf1bcf7d245471603f9 from qemu
we cannot remove the call to gen_arith() in decode_RV32_64G() since it
is used to translate multiply instructions.
Backports commit b73a987b09ad5081123dc6b1e8e6c8305a1c8673 from qemu
this splits the 64-bit only instructions into its own decode file such
that we generate the decoder for these instructions only for the RISC-V
64 bit target.
Backports commit 7e45a682edc32ba90d6955215f062210531b835b from qemu
for now only LUI & AUIPC are decoded and translated. If decodetree fails, we
fall back to the old decoder.
Backports commit 2a53cff418335ccb4719e9a94fde55f6ebcc895d from qemu
