[vector] Fix test failure with UseAVX=0 and UseAVX=1

[Lupusoru, Razvan A]

Thanks for taking a look at the fixes.

- The signature change to separate mask from xmm0 was needed because I have found that register allocator did not adhere to requests to allocate the mask in xmm0. Namely, what would happen is that mask generator (in my failed case it was a VectorLoadMask) would assign a vecD as output. Then match rule for blend would fail because constraint for mask to be in xmm0 did not get met. The only way I have found that can fix this is to explicitly ask for a temp as xmm0 and use that instead for blend.
- You are probably right that the "if" condition is unnecessary since it is incorrect to allocate temp in same register as source. I can fix that in a follow up patch.
- Regarding masks, I have found that when using UseAVX=1, there were failures. The root cause was that vector_size_supported will return false for 256 when element type is integral type. This is because AVX only supports 256-bit operations for FP. Thus there were inconsistencies for vector_size_supported when mask is integral type while user is FP type. Thus I got rid of the erasure and now masks reflect the appropriate element type (not just the integral type corresponding to appropriate bits).

Let me know if you have any more questions.

--Razvan

-----Original Message-----
From: Vladimir Ivanov [mailto:vladimir.x.ivanov at oracle.com] 
Sent: Friday, May 18, 2018 1:09 PM
To: Lupusoru, Razvan A <razvan.a.lupusoru at intel.com>; panama-dev at openjdk.java.net
Subject: Re: [vector] Fix test failure with UseAVX=0 and UseAVX=1

Razvan, can you elaborate why you

src/hotspot/cpu/x86/x86.ad:

-instruct pblendvb1L(vecD dst, vecD src, rxmm0 mask) %{
+instruct pblendvb1L(vecD dst, vecD src, vecD mask, rxmm0 xmm_0) %{
    predicate(UseAVX == 0 && UseSSE > 3 && n->as_Vector()->length() == 1 && n->bottom_type()->is_vect()->element_basic_type() == T_LONG);
    match(Set dst (VectorBlend (Binary dst src) mask));
+  effect(TEMP xmm_0);
    format %{ "pblendvb  $dst,$src,$mask\t! blend packed1L" %}
    ins_encode %{
+    if ($mask$$XMMRegister != $xmm_0$$XMMRegister) {
+      __ movdqu($xmm_0$$XMMRegister, $mask$$XMMRegister);
+    }
      __ pblendvb($dst$$XMMRegister, $src$$XMMRegister);
    %}
    ins_pipe( pipe_slow );
  %}

"$mask$$XMMRegister != $xmm_0$$XMMRegister" check looks redundant.
Is it possible for input & temp to be assigned the same register?


Also, can you, please, elaborate why you remove basic type erasure for masks? Is it because you adjusted ad rules to cover T_FLOAT & T_DOUBLE as well?

-instruct pblendvb16B(vecX dst, vecX src, rxmm0 mask) %{
+instruct pblendvb16B(vecX dst, vecX src, vecX mask, rxmm0 xmm_0) %{

-instruct pblendvb2L(vecX dst, vecX src, rxmm0 mask) %{
+instruct pblendvb2L(vecX dst, vecX src, vecX mask, rxmm0 xmm_0) %{

-instruct blendvpd2D(vecX dst, vecX src, rxmm0 mask) %{
+instruct blendvpd2D(vecX dst, vecX src, vecX mask, rxmm0 xmm_0) %{

  instruct loadmask4i(vecX dst, vecS src) %{
-  predicate(UseSSE >= 4 && n->as_Vector()->length() == 4 && 
n->bottom_type()->is_vect()->element_basic_type() == T_INT);
+  predicate(UseSSE >= 4 && n->as_Vector()->length() == 4 &&
+            (n->bottom_type()->is_vect()->element_basic_type() == T_INT ||
+             n->bottom_type()->is_vect()->element_basic_type() ==
T_FLOAT));

Best regards,
Vladimir Ivanov

On 5/18/18 12:28, Lupusoru, Razvan A wrote:
> Hi all,
> 
> The following patch fixes test failures when running tests with UseAVX=0 and UseAVX=1. Let me know if you have any comments. Thanks!
> http://cr.openjdk.java.net/~rlupusoru/panama/webrev_fixuseavx_01/index.html
> 
> --Razvan
>