diff options
Diffstat (limited to 'src/a.tex')
| -rw-r--r-- | src/a.tex | 4 |
1 files changed, 2 insertions, 2 deletions
@@ -103,7 +103,7 @@ For RV64, LR.W and SC.W sign-extend the value placed in {\em rd}. Both compare-and-swap (CAS) and LR/SC can be used to build lock-free data structures. After extensive discussion, we opted for LR/SC for several reasons: 1) CAS suffers from the ABA problem, which LR/SC -avoids because it monitors all accesses to the address rather than +avoids because it monitors all writes to the address rather than only checking for changes in the data value; 2) CAS would also require a new integer instruction format to support three source operands (address, compare value, swap value) as well as a different memory @@ -435,7 +435,7 @@ are encoded with an R-type instruction format. These AMO instructions atomically load a data value from the address in {\em rs1}, place the value into register {\em rd}, apply a binary operator to the loaded value and the original value in {\em rs2}, then store the result back -to the address in {\em rs1}. AMOs can either operate on 64-bit (RV64 +to the original address in {\em rs1}. AMOs can either operate on 64-bit (RV64 only) or 32-bit words in memory. For RV64, 32-bit AMOs always sign-extend the value placed in {\em rd}, and ignore the upper 32 bits of the original value of {\em rs2}. |