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Optimized dataset read (#211)

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* Optimized dataset read

There was a false dependency on readReg2 and readReg3 (caused by `xor rbp, rax` instruction) when reading dataset item (see design.md - 4.6.2 Loop execution, steps 5 and 7). This change uses `ma` register to read dataset item before the whole `rbp` (`ma` and `mx`) is changed, so superscalar and out-of-order CPU can start executing it earlier.

Results: https://i.imgur.com/Bpeq9mx.png

~1% speedup on modern Intel/AMD CPUs.

* ARMv8: optimized dataset read

Break dependency from readReg2 and readReg3.

* Fixed light mode hashing
This commit is contained in:
SChernykh
2021-05-22 13:54:50 +02:00
committed by GitHub
parent c12097400b
commit 3c8c7ee097
5 changed files with 20 additions and 18 deletions
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src/asm/program_read_dataset.inc
+11 -12
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@@ -1,17 +1,16 @@
mov ecx, ebp ;# ecx = ma
and ecx, RANDOMX_DATASET_BASE_MASK
xor r8, qword ptr [rdi+rcx]
ror rbp, 32 ;# swap "ma" and "mx"
xor rbp, rax ;# modify "mx"
mov edx, ebp ;# edx = mx
and edx, RANDOMX_DATASET_BASE_MASK
prefetchnta byte ptr [rdi+rdx]
ror rbp, 32 ;# swap "ma" and "mx"
mov edx, ebp ;# edx = ma
and edx, RANDOMX_DATASET_BASE_MASK
lea rcx, [rdi+rdx] ;# dataset cache line
xor r8, qword ptr [rcx+0]
xor r9, qword ptr [rcx+8]
xor r10, qword ptr [rcx+16]
xor r11, qword ptr [rcx+24]
xor r12, qword ptr [rcx+32]
xor r13, qword ptr [rcx+40]
xor r14, qword ptr [rcx+48]
xor r15, qword ptr [rcx+56]
xor r9, qword ptr [rdi+rcx+8]
xor r10, qword ptr [rdi+rcx+16]
xor r11, qword ptr [rdi+rcx+24]
xor r12, qword ptr [rdi+rcx+32]
xor r13, qword ptr [rdi+rcx+40]
xor r14, qword ptr [rdi+rcx+48]
xor r15, qword ptr [rdi+rcx+56]