[vectorIntrinsics] RFR: Different cleanups in backend C2 support

[Viswanathan, Sandhya]

Agree on all your points. On item 6) below, 4 byte vector minmax path will only come from auto-vectorizer (when vector width is restricted to 4 bytes) and not from vector API.

Best Regards,
Sandhya

-----Original Message-----
From: Vladimir Ivanov <vladimir.x.ivanov at oracle.com> 
Sent: Thursday, April 02, 2020 2:30 AM
To: Viswanathan, Sandhya <sandhya.viswanathan at intel.com>; panama-dev <panama-dev at openjdk.java.net>
Subject: Re: [vectorIntrinsics] RFR: Different cleanups in backend C2 support

Hi Sandhya,

Thanks for the review.

> 1. In x86.ad, the following set of rules are coming from mainline so changes to them could be done on mainline:
>      replicate, vector add, vector sub, mul, cmov, div, sqrt, scalar shift, and, or, xor, abs, neg, fma, muladds2i, popcount  rules
>      Of vector mul, only two rules (mulL_reg, vmul4L_reg_avx) are added in vectorIntrinsics/vector-unstable branch.

It makes perfect sense to upstream the cleanup, but I don't see a pressing need to split it into 2 parts right now. The changes can live in panama until part of them are integrated upstream. Do you see any major problems with that scenario?

> 2. The following method is defined in two places, in x86.ad and c2_MacroAssembler_x86.cpp:
> 1202 inline Assembler::AvxVectorLen vector_length_encoding(int bytes) 
> {
> 36 inline Assembler::AvxVectorLen 
> C2_MacroAssembler::vector_length_encoding(int vlen_in_bytes) {

Yes, I haven't spent much time yet looking for a proper place to put it (c2_MacroAssembler.inline.hpp maybe?), so ended up with 2 copies.

> 3. x86.ad: match_rule_supported, why remove the following for ExtractB and ExtractL?
> 1403 #ifndef _LP64
> 1404       return false;
> 1405 #endif
> 4. x86.ad: match_rule_supported, why remove the following for VectorTest?
> 1449     case Op_VectorTest:
> 1450       return false;
> 1451       break;

The checks are redundant because relevant AD instructions are absent
x86-32 and Matcher::has_match_rule() handles such cases.

> 5. x86.ad, the reference to bottom_type() in the following statement could be replaced by elem_bt:
> 3495     __ evgather(this->bottom_type()->is_vect()->element_basic_type(), $dst$$XMMRegister, ktmp, $tmp$$Register, $idx$$XMMRegister, vlen_enc);

Yes, good point.

> 6. The instructs minmax_reg and vminmax_reg can support vector_length_in_bytes == 4.

Good.

I left the comment because the original check excluded "== 4" case:

-instruct minmax_reg(vec dst, vec src) %{
-  predicate(UseSSE > 3 && UseAVX == 0 &&
-            (n->as_Vector()->length_in_bytes() == 8 ||
-             n->as_Vector()->length_in_bytes() == 16) &&
-
is_integral_type(n->bottom_type()->is_vect()->element_basic_type()) &&
-            n->bottom_type()->is_vect()->element_basic_type() != T_LONG);

But it didn't cause any problems before. It means that either the tests aren't exercise that case or such cases aren't intrinsified.

I'd like to keep the assert until we find out what's going on there.

> 7. vshiftL_arith_var instruct should have in the predicate UseAVX==2. If UseAVX > 2 then the vtmp is not required and we can directly use the evpsravq instruction (vshiftL_arith_var_evex rule) even for <=4 length.

> 8. vcastStoX:
> 6364             vector_length(n->in(1)) <= 16 && // src
>     should be
> 6364             vector_length(n->in(1)) == 16 && // src

Good catch. Will fix both.

Best regards,
Vladimir Ivanov

> -----Original Message-----
> From: panama-dev <panama-dev-bounces at openjdk.java.net> On Behalf Of 
> Vladimir Ivanov
> Sent: Wednesday, April 01, 2020 10:13 AM
> To: panama-dev <panama-dev at openjdk.java.net>
> Subject: [vectorIntrinsics] RFR: Different cleanups in backend C2 
> support
> 
> http://cr.openjdk.java.net/~vlivanov/panama/vector/cleanup.02/webrev.0
> 0/
> 
> Some cleanups in backend C2 support for Vector API.
> 
> Testing: jdk/incubator/vector tests in different configuations on a 
> Skylake machine (-XX:UseAVX=[0..3] + -XX:UseSSE=[2..4])
> 
> Best regards,
> Vladimir Ivanov
>