On Sun, Feb 17, 2019 at 10:49 AM Uros Bizjak <ubiz...@gmail.com> wrote:
>
> On Sun, Feb 17, 2019 at 6:37 PM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> > > > > > > > > On x86-64, since __m64 is returned and passed in XMM
> > > > > > > > > registers, we can
> > > > > > > > > emulate MMX intrinsics with SSE instructions. To support it,
> > > > > > > > > we added
> > > > > > > > >
> > > > > > > > > #define TARGET_MMX_WITH_SSE (TARGET_64BIT && TARGET_SSE2)
> > > > > > > > >
> > > > > > > > > ;; Define instruction set of MMX instructions
> > > > > > > > > (define_attr "mmx_isa" "base,native,x64,x64_noavx,x64_avx"
> > > > > > > > > (const_string "base"))
> > > > > > > > >
> > > > > > > > > (eq_attr "mmx_isa" "native")
> > > > > > > > > (symbol_ref "!TARGET_MMX_WITH_SSE")
> > > > > > > > > (eq_attr "mmx_isa" "x64")
> > > > > > > > > (symbol_ref "TARGET_MMX_WITH_SSE")
> > > > > > > > > (eq_attr "mmx_isa" "x64_avx")
> > > > > > > > > (symbol_ref "TARGET_MMX_WITH_SSE && TARGET_AVX")
> > > > > > > > > (eq_attr "mmx_isa" "x64_noavx")
> > > > > > > > > (symbol_ref "TARGET_MMX_WITH_SSE && !TARGET_AVX")
> > > > > > > > >
> > > > > > > > > We added SSE emulation to MMX patterns and disabled MMX
> > > > > > > > > alternatives with
> > > > > > > > > TARGET_MMX_WITH_SSE.
> > > > > > > > >
> > > > > > > > > Most of MMX instructions have equivalent SSE versions and
> > > > > > > > > results of some
> > > > > > > > > SSE versions need to be reshuffled to the right order for
> > > > > > > > > MMX. Thee are
> > > > > > > > > couple tricky cases:
> > > > > > > > >
> > > > > > > > > 1. MMX maskmovq and SSE2 maskmovdqu aren't equivalent. We
> > > > > > > > > emulate MMX
> > > > > > > > > maskmovq with SSE2 maskmovdqu by zeroing out the upper 64
> > > > > > > > > bits of the
> > > > > > > > > mask operand and handle unmapped bits 64:127 at memory
> > > > > > > > > address by
> > > > > > > > > adjusting source and mask operands together with memory
> > > > > > > > > address.
> > > > > > > > >
> > > > > > > > > 2. MMX movntq is emulated with SSE2 DImode movnti, which is
> > > > > > > > > available
> > > > > > > > > in 64-bit mode.
> > > > > > > > >
> > > > > > > > > 3. MMX pshufb takes a 3-bit index while SSE pshufb takes a
> > > > > > > > > 4-bit index.
> > > > > > > > > SSE emulation must clear the bit 4 in the shuffle control
> > > > > > > > > mask.
> > > > > > > > >
> > > > > > > > > 4. To emulate MMX cvtpi2p with SSE2 cvtdq2ps, we must
> > > > > > > > > properly preserve
> > > > > > > > > the upper 64 bits of destination XMM register.
> > > > > > > > >
> > > > > > > > > Tests are also added to check each SSE emulation of MMX
> > > > > > > > > intrinsics.
> > > > > > > > >
> > > > > > > > > There are no regressions on i686 and x86-64. For x86-64, GCC
> > > > > > > > > is also
> > > > > > > > > tested with
> > > > > > > > >
> > > > > > > > > --with-arch=native --with-cpu=native
> > > > > > > > >
> > > > > > > > > on AVX2 and AVX512F machines.
> > > > > > > >
> > > > > > > > An idea that would take patch a step further also on 32 bit
> > > > > > > > targets:
> > > > > > > >
> > > > > > > > *Assuming* that operations on XMM registers are as fast (or
> > > > > > > > perhaps
> > > > > > > > faster) than operations on MMX registers, we can change mmx_isa
> > > > > > > > attribute in e.g.
> > > > > > > >
> > > > > > > > + "@
> > > > > > > > + p<logic>\t{%2, %0|%0, %2}
> > > > > > > > + p<logic>\t{%2, %0|%0, %2}
> > > > > > > > + vp<logic>\t{%2, %1, %0|%0, %1, %2}"
> > > > > > > > + [(set_attr "mmx_isa" "native,x64_noavx,x64_avx")
> > > > > > > >
> > > > > > > > to:
> > > > > > > >
> > > > > > > > [(set_attr "isa" "*,noavx,avx")
> > > > > > > > (set_attr "mmx_isa" "native,*,*")]
> > > > > > > >
> > > > > > > > So, for x86_64 everything stays the same, but for x86_32 we now
> > > > > > > > allow
> > > > > > > > intrinsics to use xmm registers in addition to mmx registers.
> > > > > > > > We can't
> > > > > > > > disable MMX for x64_32 anyway due to ISA constraints (and some
> > > > > > > > tricky
> > > > > > > > cases, e.g. monvti that works only for 64bit targets and e.g.
> > > > > > > > maskmovq
> > > > > > > > & similar, which are more efficient with MMX regs), but RA has
> > > > > > > > much
> > > > > > > > more freedom to allocate the most effective register set even
> > > > > > > > for
> > > > > > > > 32bit targets.
> > > > > > > >
> > > > > > > > WDYT?
> > > > > > > >
> > > > > > >
> > > > > > > Since MMX registers are used to pass and return __m64 values,
> > > > > > > we can't really get rid of MMX instructions in 32-bit mode. If
> > > > > > > people
> > > > > > > have to stay with 32-bit mode, they need MMX. I don't think we
> > > > > > > should
> > > > > > > extend TARGET_MMX_WITH_SSE to 32-bit mode.
> > > > > >
> > > > > > No, TARGET_MMX_WITH_SSE is still enabled only for 64bit targets. We
> > > > > > should not *disable* SSE alternatives on 32bit targets.
> > > >
> > > > I don't think my patch set disables any SSE alternatives in 32-bit
> > > > mode. However,
> > > > it DOES NOT enable any SSE alternatives in 32-bit mode. To really
> > > > enable SSE
> > > > alternatives in
> > > >
> > > > (define_insn "*mmx_<code><mode>3"
> > > > [(set (match_operand:MMXMODEI 0 "register_operand" "=y,x,Yv")
> > > > (any_logic:MMXMODEI
> > > > (match_operand:MMXMODEI 1 "register_mmxmem_operand" "%0,0,Yv")
> > > > (match_operand:MMXMODEI 2 "register_mmxmem_operand"
> > > > "ym,x,Yv")))]
> > > > "(TARGET_MMX || TARGET_MMX_WITH_SSE)
> > > > && ix86_binary_operator_ok (<CODE>, <MODE>mode, operands)"
> > > > "@
> > > > p<logic>\t{%2, %0|%0, %2}
> > > > p<logic>\t{%2, %0|%0, %2}
> > > > vp<logic>\t{%2, %1, %0|%0, %1, %2}"
> > > > [(set_attr "mmx_isa" "native,x64_noavx,x64_avx")
> > > > (set_attr "type" "mmxadd,sselog,sselog")
> > > > (set_attr "mode" "DI,TI,TI")])
> > > >
> > > > register_mmxmem_operand must return true for SSE alternatives:
> > >
> > > It returns true for register and memory operands for 32bit targets,
> > > because
> > >
> > > #define TARGET_MMX_WITH_SSE (TARGET_64BIT && TARGET_SSE2)
> >
> > Will
> >
> > (match_operand:V4HI 2 "nonimmediate_operand" "ym,x,Yv"))))]
> >
> > work well with RA? I got some wrong code before register_mmxmem_operand
> > was added to match "ym,x,Yv".
>
> I see no reason why it shouldn't.
This will be equivalent to replace register_operand in
[(match_operand:VI1_AVX512VLBW 1 "register_operand" "v")
with nonimmediate_operand. If it should work, I can do it in i386.md and
sse.md to check it out.
--
H.J.
