On Sun, Feb 17, 2019 at 9:27 AM Uros Bizjak <ubiz...@gmail.com> wrote:
>
> On Sun, Feb 17, 2019 at 6:10 PM H.J. Lu <hjl.to...@gmail.com> wrote:
> >
> > On Sun, Feb 17, 2019 at 7:57 AM Uros Bizjak <ubiz...@gmail.com> wrote:
> > >
> > > On Sun, Feb 17, 2019 at 4:53 PM Uros Bizjak <ubiz...@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".
> > ;; Match register operands, but include memory operands for
> > ;; !TARGET_MMX_WITH_SSE.
> > (define_predicate "register_mmxmem_operand"
> > (ior (match_operand 0 "register_operand")
> > (and (not (match_test "TARGET_MMX_WITH_SSE"))
> > (match_operand 0 "memory_operand"))))
> >
> > How do you enable SSE alternatives in 32-bit mode without enabling
> > TARGET_MMX_WITH_SSE for 32-bit mode?
>
> Check the new attribute definitions below:
> > > The correct isa attribute definition would be:
> > >
> > > [(set_attr "isa" "*,sse2_noavx,avx")
> > > (set_attr "mmx_isa" "native,*,*")]
>
> Uros.
--
H.J.
