[jdk16] Integrated: 8258703: Incorrect 512-bit vector registers restore on x86_32
Jie Fu
jiefu at openjdk.java.net
Mon Jan 4 23:44:58 UTC 2021
On Wed, 23 Dec 2020 09:06:00 GMT, Jie Fu <jiefu at openjdk.org> wrote:
> Hi all,
>
> Following tests fail on our AVX512 machines with x86_32:
> - compiler/runtime/Test7196199.java
> - compiler/runtime/safepoints/TestRegisterRestoring.java
> - compiler/vectorization/TestVectorsNotSavedAtSafepoint.java
>
> The reason is that 512-bit registers (zmm0 ~ zmm7) are restored incorrectly.
>
> Current restore logic for 512-bit registers includes:
> 1) restore zmm[511..256] [1]
> 2) restore zmm[255..128] [2] <-- Wrong on AVX512 with avx512vl
>
> On our AVX512 machine, Assembler::vinsertf128 [3] was called in step 2).
> According to the Intel instruction set reference, vinsertf128 just copies the lower half of zmm, which lost the upper half of zmm.
> VINSERTF128 (VEX encoded version)
> TEMP[255:0] <- SRC1[255:0]
> CASE (imm8[0]) OF
> 0: TEMP[127:0] <- SRC2[127:0]
> 1: TEMP[255:128] <- SRC2[127:0]
> ESAC
> DEST <- TEMP
>
> The fix just changes the order of the restore logic for 512-bit registers:
> 1) restore zmm[255..128]
> 2) restore zmm[511..256]
>
> Thanks.
> Best regards,
> Jie
>
> [1] https://github.com/openjdk/jdk16/blob/master/src/hotspot/cpu/x86/sharedRuntime_x86_32.cpp#L320
> [2] https://github.com/openjdk/jdk16/blob/master/src/hotspot/cpu/x86/sharedRuntime_x86_32.cpp#L326
> [3] https://github.com/openjdk/jdk16/blob/master/src/hotspot/cpu/x86/macroAssembler_x86.hpp#L1463
This pull request has now been integrated.
Changeset: 216c2ec0
Author: Jie Fu <jiefu at openjdk.org>
URL: https://git.openjdk.java.net/jdk16/commit/216c2ec0
Stats: 12 lines in 1 file changed: 6 ins; 5 del; 1 mod
8258703: Incorrect 512-bit vector registers restore on x86_32
Reviewed-by: kvn, sviswanathan
-------------
PR: https://git.openjdk.java.net/jdk16/pull/64
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