diff options
Diffstat (limited to 'src/cmd/internal/obj')
| -rw-r--r-- | src/cmd/internal/obj/loong64/doc.go | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/src/cmd/internal/obj/loong64/doc.go b/src/cmd/internal/obj/loong64/doc.go index 6ec53e7a17..e4c33f6525 100644 --- a/src/cmd/internal/obj/loong64/doc.go +++ b/src/cmd/internal/obj/loong64/doc.go @@ -88,5 +88,29 @@ Examples: MOVB R6, (R4)(R5) <=> stx.b R6, R5, R5 MOVV R6, (R4)(R5) <=> stx.d R6, R5, R5 MOVV F6, (R4)(R5) <=> fstx.d F6, R5, R5 + +# Special instruction encoding definition and description on LoongArch + + 1. DBAR hint encoding for LA664(Loongson 3A6000) and later micro-architectures, paraphrased + from the Linux kernel implementation: https://git.kernel.org/torvalds/c/e031a5f3f1ed + + - Bit4: ordering or completion (0: completion, 1: ordering) + - Bit3: barrier for previous read (0: true, 1: false) + - Bit2: barrier for previous write (0: true, 1: false) + - Bit1: barrier for succeeding read (0: true, 1: false) + - Bit0: barrier for succeeding write (0: true, 1: false) + - Hint 0x700: barrier for "read after read" from the same address + + Traditionally, on microstructures that do not support dbar grading such as LA464 + (Loongson 3A5000, 3C5000) all variants are treated as “dbar 0” (full barrier). + +2. Notes on using atomic operation instructions + + - AM*_DB.W[U]/V[U] instructions such as AMSWAPDBW not only complete the corresponding + atomic operation sequence, but also implement the complete full data barrier function. + + - When using the AM*_.W[U]/D[U] instruction, registers rd and rj cannot be the same, + otherwise an exception is triggered, and rd and rk cannot be the same, otherwise + the execution result is uncertain. */ package loong64 |