On Tue, Jul 15, 2014 at 1:01 PM, Ilya Enkovich <enkovich....@gmail.com> wrote: > On 15 Jul 10:42, Uros Bizjak wrote: >> On Tue, Jul 15, 2014 at 10:25 AM, Ilya Enkovich <enkovich....@gmail.com> >> wrote: >> >> >>>>> Also fully restrict xmm8-15 does not seem right. It is just costly >> >>>>> but not fully disallowed. >> >>>> >> >>>> As said earlier, you can try "Ya*x" as a constraint. >> >>> >> >>> I tried it. It does not seem to affect allocation much. I do not see >> >>> any gain on targeted tests. >> >> >> >> Strange, because the documentation claims: >> >> >> >> '*' >> >> Says that the following character should be ignored when choosing >> >> register preferences. '*' has no effect on the meaning of the >> >> constraint as a constraint, and no effect on reloading. For LRA >> >> '*' additionally disparages slightly the alternative if the >> >> following character matches the operand. >> >> >> >> Let me rethink this a bit. Prehaps we could reconsider Jakub's >> >> proposal with "Ya,!x" (with two alternatives). IIRC this approach was >> >> needed for some MMX alternatives, where we didn't want RA to allocate >> >> a MMX register when the value could be passed in integer regs, but the >> >> value was still allowed in MMX register. >> > >> > That's is what my patch already does, but with '?' instead of '!'. >> >> Yes, I know. The problem is, that Ya*x type conditional allocation >> worked OK in the past for "not preferred, but still alowed regclass" >> registers, There are several patterns in i386.md that live by this >> premise, including movsf_internal and movdf_internal. If this approach >> doesn't work anymore, then we have to either figure out what is the >> reason, or invent a new strategy that will be applicable to all cases. >> >> Can you please post a small test that illustrates the case where Ya,!x >> works, but Ya*x doesn't? > > It's hard to compose a small testcase which will have SSE4 instructions > generated with required register usage. I use tcpjumbo test from TCPmark for > initial check of how my patch works. This test has a lot of pmovzxwd > instructions generated and many of them use xmm8-15. I tried two versions of > a simple patch which modifies only pmovzxwd instruction. > > Patch1: > > diff --git a/gcc/config/i386/sse.md b/gcc/config/i386/sse.md > index d907353..6b03b72 100644 > --- a/gcc/config/i386/sse.md > +++ b/gcc/config/i386/sse.md > @@ -11852,10 +11852,10 @@ > (set_attr "mode" "OI")]) > > (define_insn "sse4_1_<code>v4hiv4si2" > - [(set (match_operand:V4SI 0 "register_operand" "=x") > + [(set (match_operand:V4SI 0 "register_operand" "=Yr,!x") > (any_extend:V4SI > (vec_select:V4HI > - (match_operand:V8HI 1 "nonimmediate_operand" "xm") > + (match_operand:V8HI 1 "nonimmediate_operand" "Yr,!xm") > (parallel [(const_int 0) (const_int 1) > (const_int 2) (const_int 3)]))))] > "TARGET_SSE4_1" > > Patch2: > > diff --git a/gcc/config/i386/sse.md b/gcc/config/i386/sse.md > index d907353..b3721c4 100644 > --- a/gcc/config/i386/sse.md > +++ b/gcc/config/i386/sse.md > @@ -11852,10 +11852,10 @@ > (set_attr "mode" "OI")]) > > (define_insn "sse4_1_<code>v4hiv4si2" > - [(set (match_operand:V4SI 0 "register_operand" "=x") > + [(set (match_operand:V4SI 0 "register_operand" "=Yr*x") > (any_extend:V4SI > (vec_select:V4HI > - (match_operand:V8HI 1 "nonimmediate_operand" "xm") > + (match_operand:V8HI 1 "nonimmediate_operand" "Yr*xm") > (parallel [(const_int 0) (const_int 1) > (const_int 2) (const_int 3)]))))] > "TARGET_SSE4_1" > > > Here are results of looking for pmovzxwd in resulting binaries: > #objdump -d tcpjumbo-orig | grep pmovzxwd | grep > "xmm8\|xmm9\|xmm10\|xmm11\|xmm12\|xmm13\|xmm14\|xmm15" | wc -l > 76 > #objdump -d tcpjumbo-patch1 | grep pmovzxwd | grep > "xmm8\|xmm9\|xmm10\|xmm11\|xmm12\|xmm13\|xmm14\|xmm15" | wc -l > 0 > #objdump -d tcpjumbo-patch2 | grep pmovzxwd | grep > "xmm8\|xmm9\|xmm10\|xmm11\|xmm12\|xmm13\|xmm14\|xmm15" | wc -l > 76 > > Therefore I make a conclusion that Yr*x does not really differ much from x.
Just FTR: Using "Yr,*x" is also a viable option: #objdump -d tcpjumbo-patch3 | grep pmovzxwd | grep "xmm8\|xmm9\|xmm10\|xmm11\|xmm12\|xmm13\|xmm14\|xmm15" | wc -l 0 I believe that the above is the way to go with LRA. Vladimir, what do you think? Uros.
