8287835: Add support for additional float/double to integral conversion for x86 #9032

sviswa7 · 2022-06-04T22:13:32Z

Currently the C2 JIT only supports float -> int and double -> long conversion for x86.
This PR adds the support for following conversions in the c2 JIT:
float -> long, short, byte
double -> int, short, byte

The performance gain is as follows.
Before the patch:
Benchmark Mode Cnt Score Error Units
VectorFPtoIntCastOperations.microDouble2Byte thrpt 3 32367.971 ± 6161.118 ops/ms
VectorFPtoIntCastOperations.microDouble2Int thrpt 3 25825.251 ± 5417.104 ops/ms
VectorFPtoIntCastOperations.microDouble2Long thrpt 3 59641.958 ± 17307.177 ops/ms
VectorFPtoIntCastOperations.microDouble2Short thrpt 3 29641.505 ± 12023.015 ops/ms
VectorFPtoIntCastOperations.microFloat2Byte thrpt 3 16271.224 ± 1523.083 ops/ms
VectorFPtoIntCastOperations.microFloat2Int thrpt 3 59199.994 ± 14357.959 ops/ms
VectorFPtoIntCastOperations.microFloat2Long thrpt 3 17169.197 ± 1738.273 ops/ms
VectorFPtoIntCastOperations.microFloat2Short thrpt 3 14934.139 ± 2329.253 ops/ms

After the patch:
Benchmark Mode Cnt Score Error Units
VectorFPtoIntCastOperations.microDouble2Byte thrpt 3 115436.659 ± 21282.364 ops/ms
VectorFPtoIntCastOperations.microDouble2Int thrpt 3 87194.395 ± 9443.106 ops/ms
VectorFPtoIntCastOperations.microDouble2Long thrpt 3 59652.356 ± 7240.721 ops/ms
VectorFPtoIntCastOperations.microDouble2Short thrpt 3 110570.719 ± 10401.620 ops/ms
VectorFPtoIntCastOperations.microFloat2Byte thrpt 3 110028.539 ± 11113.137 ops/ms
VectorFPtoIntCastOperations.microFloat2Int thrpt 3 59469.193 ± 18272.495 ops/ms
VectorFPtoIntCastOperations.microFloat2Long thrpt 3 59897.101 ± 7249.268 ops/ms
VectorFPtoIntCastOperations.microFloat2Short thrpt 3 86167.554 ± 8253.232 ops/ms

Please review.

Best Regards,
Sandhya

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Issue

JDK-8287835: Add support for additional float/double to integral conversion for x86

Reviewers

Vladimir Kozlov (@vnkozlov - Reviewer) ⚠️ Review applies to 996ee049
Jatin Bhateja (@jatin-bhateja - Committer)

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bridgekeeper · 2022-06-04T22:14:31Z

👋 Welcome back sviswanathan! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2022-06-04T22:17:10Z

@sviswa7 The following labels will be automatically applied to this pull request:

core-libs
hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

sviswa7 · 2022-06-04T22:20:28Z

/label remove core-libs

openjdk · 2022-06-04T22:21:08Z

@sviswa7
The core-libs label was successfully removed.

mlbridge · 2022-06-04T22:40:00Z

Webrevs

vnkozlov

I assume it is support for "vector conversion".

Please, add IR framework test.

vnkozlov · 2022-06-05T01:37:37Z

src/hotspot/cpu/x86/x86.ad

+          (is_subword_type(bt) || bt == T_LONG)) {
+        return false;
+      }
+      if ((bt == T_LONG) && !VM_Version::supports_avx512dq()) {


Again overlapping conditions. So T_LONG requires both: AVX512, avx512vl and avx512dq?

What about T_INT?

T_INT doesn't need AVX512dq. Float to long conversion (T_LONG) uses evcvttps2qq, which needs AVX512dq.

Okay. I see that there are 2 instructions to support F2I by using avx or evex encoding. They cover all cases.
No you are introducing sub_integer and long types only for evex encoding.

You need comment that F2I is supported in all cases. For other integral types you need 512vl and additionally 512dq for T_LONG.

Note, you don't need to check (UseAVX <= 2) because avx512vl bit is cleaned in such case. It is the same for VectorCastD2X code.

In such case I suggest:

if (is_subword_type(bt) && !VM_Version::supports_avx512vl() || (bt == T_LONG) && !VM_Version::supports_avx512vldq()) { return false; }

vnkozlov · 2022-06-05T01:41:02Z

src/hotspot/cpu/x86/x86.ad

+  predicate(((VM_Version::supports_avx512vl() ||
+              Matcher::vector_length_in_bytes(n) == 64)) &&
+             is_integral_type(Matcher::vector_element_basic_type(n)));


Do we need some of these conditions since you have them already in match_rule_supported_vector()?

The predicate is not correct for all types this instruction is used now: it says that if size is 64 bytes you don't need avx512vl support for all types. Is it true?

All this is very confusing. I suggest to keep original castFtoI_reg_evex() instruction as it was and use new castFtoX_reg_evex() only for T_LONG and sub_integer with new predicate (type != T_INT) and additional conditions if needed.

Yes it was needed to select between the rules. On platforms that don't support avx512vl, we use AVX512 instructions only for 512-bit vectors and AVX instructions for < 64 byte vectors.

vnkozlov · 2022-06-05T01:42:40Z

src/hotspot/cpu/x86/x86.ad

+      if (((UseAVX <= 2) || (!VM_Version::supports_avx512vl())) &&
+          (is_subword_type(bt) || bt == T_INT)) {
        return false;
      }
-      if (bt == T_LONG && !VM_Version::supports_avx512dq()) {
+      if (is_integral_type(bt) && !VM_Version::supports_avx512dq()) {
        return false;
      }


Overlapping conditions for the same types are confusing.

I will add comments and rephrase the checks to make it clearer.

vnkozlov · 2022-06-06T18:54:33Z

src/hotspot/cpu/x86/x86.ad

+  predicate(((VM_Version::supports_avx512vl() ||
+              Matcher::vector_length_in_bytes(n) == 64)) &&
+             is_integral_type(Matcher::vector_element_basic_type(n)));


The predicate is not correct for all types this instruction is used now: it says that if size is 64 bytes you don't need avx512vl support for all types. Is it true?

All this is very confusing. I suggest to keep original castFtoI_reg_evex() instruction as it was and use new castFtoX_reg_evex() only for T_LONG and sub_integer with new predicate (type != T_INT) and additional conditions if needed.

vnkozlov · 2022-06-06T19:04:56Z

src/hotspot/cpu/x86/x86.ad

      break;
    case Op_VectorCastD2X:
-      if (is_subword_type(bt) || bt == T_INT) {
+      if (((UseAVX <= 2) || (!VM_Version::supports_avx512vl())) &&


Which asm instructions are required avx512vl? I don't see asserts in assembler_x86.cpp

avx512vl support is needed only for vectors < 512 bit. I have corrected this in the predicate.

sviswa7 · 2022-06-06T21:27:53Z

@vnkozlov I have implemented your review comments. The only item remaining is to add IR framework test.

vnkozlov

Looks good. Will wait IR test before testing and approval.

sviswa7 · 2022-06-06T23:19:39Z

@vnkozlov I have added the IR framework test case. Please take a look.

vnkozlov

Good. I will start testing.

openjdk · 2022-06-06T23:53:57Z

@sviswa7 This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8287835: Add support for additional float/double to integral conversion for x86

Reviewed-by: kvn, jbhateja

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 86 new commits pushed to the master branch:

e01cd7c: 8284780: Need methods to create pre-sized HashSet and LinkedHashSet
a941bc2: 8288082: Build failure due to clang_major is not defined after JDK-8214976
65f0829: 8288068: Javadoc contains spurious reference to CLinker
130ce7c: 8288052: Small logging clarification during failed heap shrinkage
b623398: 8287901: Loom: Failures with -XX:+VerifyStack
04f02ac: 8214976: Warn about uses of functions replaced for portability
024a240: 8287333: Clean up ParamTaglet and ThrowsTaglet
c8cff1b: 8202449: overflow handling in Random.doubles
c15e10f: 8233760: Result of BigDecimal.toString throws overflow exception on new BigDecimal(str)
b92ce26: 8281001: Class::forName(String) defaults to system class loader if the caller is null
... and 76 more: https://git.openjdk.java.net/jdk/compare/a6fc485a22484b70daf170e981432c0856b9d93d...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

vnkozlov

Results are good.
You need second review.

sviswa7 · 2022-06-07T13:18:36Z

@vnkozlov Thanks a lot for the review and test.
@jatin-bhateja Could you please review this PR. It is an extension of your earlier work.

jatin-bhateja · 2022-06-08T12:47:37Z

src/hotspot/cpu/x86/x86.ad

+      if (to_elem_bt == T_SHORT) {
+        __ evpmovdw($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+      } else {
+        assert(to_elem_bt == T_BYTE, "required");
+        __ evpmovdb($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+      }


We do support F2I cast on AVX2 and that can be extended for sub-word types using
signed saturated lane packing instructions (PACKSSDW and PACKSSWB).

I will file a separate RFE for this.

Link to RFE: https://bugs.openjdk.org/browse/JDK-8288043

jatin-bhateja · 2022-06-08T12:51:40Z

src/hotspot/cpu/x86/x86.ad

+    int vlen_enc = vector_length_encoding(this, $src);
    __ vector_castD2L_evex($dst$$XMMRegister, $src$$XMMRegister, $xtmp1$$XMMRegister,
                           $xtmp2$$XMMRegister, $ktmp1$$KRegister, $ktmp2$$KRegister,
                           ExternalAddress(vector_double_signflip()), $scratch$$Register, vlen_enc);
+    BasicType to_elem_bt = Matcher::vector_element_basic_type(this);
+    if (to_elem_bt != T_LONG) {
+      switch(to_elem_bt) {
+        case T_INT:
+          __ evpmovsqd($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+          break;
+        case T_SHORT:
+          __ evpmovsqd($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+          __ evpmovdw($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+          break;
+        case T_BYTE:
+          __ evpmovsqd($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+          __ evpmovdb($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+          break;
+        default: assert(false, "%s", type2name(to_elem_bt));
+      }


Please move this to a macro assembly routine named vector_castD2X_evex

jatin-bhateja · 2022-06-08T13:03:57Z

src/hotspot/cpu/x86/x86.ad

+      switch(to_elem_bt) {
+        case T_INT:
+          __ evpmovsqd($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+          break;
+        case T_SHORT:
+          __ evpmovsqd($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+          __ evpmovdw($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+          break;
+        case T_BYTE:
+          __ evpmovsqd($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);
+          __ evpmovdb($dst$$XMMRegister, $dst$$XMMRegister, vlen_enc);


Sub-word handling can be extended for AVX2 using packing instruction sequence similar to VectorStoreMask for quad ward lanes.

D2X in general needs AVX 512 due to evcvttpd2qq.

Thanks @sviswa7 , for AVX we can use VCVTTPD2DQ to cast double precison lane to integer and subsequently to sub words lanes. For casting to long we do not have direct instruction.

Thanks @jatin-bhateja. I have updated the RFE (https://bugs.openjdk.org/browse/JDK-8288043) to include this.

jatin-bhateja · 2022-06-08T13:10:12Z

test/hotspot/jtreg/compiler/vectorapi/VectorFPtoIntCastTest.java

+    private static final VectorSpecies<Float> fspec512 = FloatVector.SPECIES_512;
+    private static final VectorSpecies<Double> dspec512 = DoubleVector.SPECIES_512;


Unused declarations.

jatin-bhateja · 2022-06-08T13:19:16Z

test/micro/org/openjdk/bench/jdk/incubator/vector/VectorFPtoIntCastOperations.java

+
+    @Benchmark
+    public IntVector microFloat2Int() {
+        return (IntVector)fvec512.convertShape(VectorOperators.F2I, IntVector.SPECIES_512, 0);


We can remove explicit cast by setting return type to Vector

Applicable to all cases.

sviswa7 · 2022-06-08T16:31:55Z

@jatin-bhateja I have implemented your review comments. Please take a look.

jatin-bhateja · 2022-06-09T02:08:24Z

Thanks @sviswa7

sviswa7 · 2022-06-09T18:14:28Z

@vnkozlov Could I go ahead and integrate? There were some minor changes and code rearrangement after your last test. Please let me know.

vnkozlov · 2022-06-09T18:40:24Z

I submitted new testing.

sviswa7 · 2022-06-09T20:21:52Z

Thanks a lot Vladimir!

vnkozlov · 2022-06-10T01:23:55Z

@sviswa7 testing results are good. You can push.

jatin-bhateja · 2022-06-10T07:37:59Z

test/hotspot/jtreg/compiler/vectorapi/VectorFPtoIntCastTest.java

+        for (int i = 0; i < COUNT; i++) {
+            float_arr[i] = ran.nextFloat();
+            double_arr[i] = ran.nextDouble();
+        }


Can you kindly also add special floating point values NaN, +/-Inf, +/-0.0 to input array to cover your special handling code changes.

@jatin-bhateja The test is only checking the IR node generation for x86.
The rest of the actual functionality test is already covered under the following including the special cases:
compiler/codegen/TestByteDoubleVect.java compiler/codegen/TestByteFloatVect.java compiler/codegen/TestShortFloatVect.java compiler/codegen/TestShortDoubleVect.java compiler/codegen/TestLongFloatVect.java compiler/codegen/TestIntDoubleVect.java compiler/codegen/TestIntFloatVect.java
The general idea of this PR was to complement x86 FP to integral conversion along with https://git.openjdk.org/jdk/pull/7806 from Fei Gao.

sviswa7 · 2022-06-10T17:01:32Z

/integrate

openjdk · 2022-06-10T17:02:45Z

Going to push as commit 2cc40af.
Since your change was applied there have been 111 commits pushed to the master branch:

3ee1e60: 8288132: Update test artifacts in QuoVadis CA interop tests
512db0f: 8271838: AmazonCA.java interop test fails
fcb35ed: 8287743: javax/swing/text/CSSBorder/6796710/bug6796710.java failed
bdd64d6: 8288181: AArch64: clean up out-of-date comments
5d0e8b6: 8288203: runtime/ClassUnload/UnloadTestWithVerifyDuringGC.java fails with release VMs
975316e: 8287902: UnreadableRB case in MissingResourceCauseTest is not working reliably on Windows
0901548: 8283724: Incorrect description for jtreg-failure-handler option
dae4c49: 8286197: C2: Optimize MemorySegment shape in int loop
94b473e: 8280454: G1: ClassLoaderData verification keeps CLDs live that causes problems with VerifyDuringGC during Remark
900d967: 8287924: Avoid redundant HashMap.containsKey call in EnvHelp.mapToHashtable
... and 101 more: https://git.openjdk.org/jdk/compare/a6fc485a22484b70daf170e981432c0856b9d93d...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-06-10T17:02:59Z

@sviswa7 Pushed as commit 2cc40af.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

8287835: Add support for float/double to integral conversion for x86

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sviswa7 changed the title ~~8287835: Add support for float/double to integral conversion for x86~~ 8287835: Add support for additional float/double to integral conversion for x86 Jun 4, 2022

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sviswa7 deleted the fpconvert branch June 3, 2024 21:40

		private static final VectorSpecies<Float> fspec512 = FloatVector.SPECIES_512;
		private static final VectorSpecies<Double> dspec512 = DoubleVector.SPECIES_512;

8287835: Add support for additional float/double to integral conversion for x86 #9032

8287835: Add support for additional float/double to integral conversion for x86 #9032

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