[OpenBLAS] Add v0.3.20

[giordano]

No description provided.

[giordano]

@Keno: OpenMathLib/OpenBLAS#3052 supposedly fixed the issue you reported at OpenMathLib/OpenBLAS#2998, did you ever get a chance to verify whether we can drop this patch now?

[Keno]

No idea

[giordano]

For the record, I verified the patch should now be redundant, as vanilla OpenBLAS now produces the right result: #7202 (comment).

[giordano]

When building for x86_64 with GCC and libgfortran3 (so GCC 6):

[17:11:19] ../libopenblas64_p-r0.3.20.a(dgemm_small_kernel_nn_SKYLAKEX.o): In function `dgemm_small_kernel_nn_SKYLAKEX':
[17:11:19] dgemm_small_kernel_nn_skylakex.c:(.text+0x2ddd): undefined reference to `_mm512_reduce_add_pd'
[17:11:19] dgemm_small_kernel_nn_skylakex.c:(.text+0x2e1c): undefined reference to `_mm512_reduce_add_pd'
[17:11:19] dgemm_small_kernel_nn_skylakex.c:(.text+0x2e8e): undefined reference to `_mm512_reduce_add_pd'
[17:11:19] dgemm_small_kernel_nn_skylakex.c:(.text+0x2eea): undefined reference to `_mm512_reduce_add_pd'
[17:11:19] dgemm_small_kernel_nn_skylakex.c:(.text+0x30c7): undefined reference to `_mm512_reduce_add_pd'
[17:11:19] ../libopenblas64_p-r0.3.20.a(dgemm_small_kernel_nn_SKYLAKEX.o):dgemm_small_kernel_nn_skylakex.c:(.text+0x3106): more undefined references to `_mm512_reduce_add_pd' follow
[17:11:19] ../libopenblas64_p-r0.3.20.a(sgemm_small_kernel_nn_SKYLAKEX.o): In function `sgemm_small_kernel_nn_SKYLAKEX':
[17:11:19] sgemm_small_kernel_nn_skylakex.c:(.text+0x2ca3): undefined reference to `_mm512_reduce_add_ps'
[17:11:19] sgemm_small_kernel_nn_skylakex.c:(.text+0x2cdc): undefined reference to `_mm512_reduce_add_ps'
[17:11:19] sgemm_small_kernel_nn_skylakex.c:(.text+0x2d42): undefined reference to `_mm512_reduce_add_ps'
[17:11:19] sgemm_small_kernel_nn_skylakex.c:(.text+0x2d95): undefined reference to `_mm512_reduce_add_ps'
[17:11:19] sgemm_small_kernel_nn_skylakex.c:(.text+0x2f25): undefined reference to `_mm512_reduce_add_ps'
[17:11:19] ../libopenblas64_p-r0.3.20.a(sgemm_small_kernel_nn_SKYLAKEX.o):sgemm_small_kernel_nn_skylakex.c:(.text+0x2f5e): more undefined references to `_mm512_reduce_add_ps' follow
[17:11:19] collect2: error: ld returned 1 exit status

OpenMathLib/OpenBLAS#3530 looks relevant, it appears GCC headers in v6 were wrong. This wouldn't even be the first time we hit similar issues when building OpenBLAS, see #2142, #2385, #2389, #2415. Sigh. Edit: for reference, this should be the change which introduced the new intrinsics in GCC: gcc-mirror/gcc@167a5b7