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author | Bill Traynor <wmat@riscv.org> | 2022-12-30 10:29:47 -0500 |
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committer | Bill Traynor <wmat@riscv.org> | 2022-12-30 10:29:47 -0500 |
commit | 3ee97093055776cfddd3ba6cc3bda6940309690a (patch) | |
tree | f7555ad7e58ec6792faeebc87757160de8e80601 /src/colophon.adoc | |
parent | 15322920b281458a100a6375262d6516e8671a45 (diff) | |
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diff --git a/src/colophon.adoc b/src/colophon.adoc index 0d1afb0..0106820 100644 --- a/src/colophon.adoc +++ b/src/colophon.adoc @@ -194,11 +194,11 @@ their semantics, has been defined. * The "Ztso" extension, which enforces a stricter memory consistency model than RVWMO, has been defined. * Improvements to the description and commentary. -* Defined the term IALIGN as shorthand to describe the +* Defined the term `IALIGN` as shorthand to describe the instruction-address alignment constraint. -* Removed text of P extension chapter as now superseded by active task +* Removed text of `P` extension chapter as now superseded by active task group documents. -* Removed text of V extension chapter as now superseded by separate +* Removed text of `V` extension chapter as now superseded by separate vector extension draft document. *_Preface to Document Version 2.2_* @@ -243,21 +243,21 @@ and this and future versions of this document will be released under the same license. * Rearranged chapters to put all extensions first in canonical order. * Improvements to the description and commentary. -* Modified implicit hinting suggestion on JALR to support more efficient -macro-op fusion of LUI/JALR and AUIPC/JALR pairs. +* Modified implicit hinting suggestion on `JALR` to support more efficient +macro-op fusion of `LUI/JALR` and `AUIPC/JALR` pairs. * Clarification of constraints on load-reserved/store-conditional sequences. * A new table of control and status register (CSR) mappings. -* Clarified purpose and behavior of high-order bits of *fcsr*. -* Corrected the description of the FNMADD._fmt_ and FNMSUB._fmt_ +* Clarified purpose and behavior of high-order bits of `fcsr`. +* Corrected the description of the `FNMADD`._fmt_ and `FNMSUB`._fmt_ instructions, which had suggested the incorrect sign of a zero result. -* Instructions FMV.S.X and FMV.X.S were renamed to FMV.W.X and FMV.X.W +* Instructions `FMV.S.X` and `FMV.X.S` were renamed to `FMV.W.X` and `FMV.X.W` respectively to be more consistent with their semantics, which did not change. The old names will continue to be supported in the tools. * Specified behavior of narrower (latexmath:[$<$]FLEN) floating-point values held in wider `f` registers using NaN-boxing model. * Defined the exception behavior of FMA(latexmath:[$\infty$], 0, qNaN). -* Added note indicating that the P extension might be reworked into an +* Added note indicating that the `P` extension might be reworked into an integer packed-SIMD proposal for fixed-point operations using the integer registers. * A draft proposal of the V vector instruction-set extension. @@ -270,7 +270,7 @@ by the RISC-V ELF psABI Specification cite:[riscv-elf-psabi]. *_Preface to Document Version 2.1_* This is version 2.1 of the document describing the RISC-V user-level -architecture. Note the frozen user-level ISA base and extensions IMAFDQ +architecture. Note the frozen user-level ISA base and extensions `IMAFDQ` version 2.0 have not changed from the previous version of this document cite:[riscvtr2], but some specification holes have been fixed and the documentation has been improved. Some changes have been made to the @@ -284,20 +284,20 @@ avoid moving the _rd_ specifier in very long instruction formats. the counter registers are introduced, as opposed to only being introduced later in the floating-point section (and the companion privileged architecture manual). -* The SCALL and SBREAK instructions have been renamed to ECALL and -EBREAK, respectively. Their encoding and functionality are unchanged. +* The SCALL and SBREAK instructions have been renamed to `ECALL` and +`EBREAK`, respectively. Their encoding and functionality are unchanged. * Clarification of floating-point NaN handling, and a new canonical NaN value. * Clarification of values returned by floating-point to integer conversions that overflow. -* Clarification of LR/SC allowed successes and required failures, +* Clarification of `LR/SC` allowed successes and required failures, including use of compressed instructions in the sequence. -* A new RV32E base ISA proposal for reduced integer register counts, -supports MAC extensions. +* A new `RV32E` base ISA proposal for reduced integer register counts, +supports `MAC` extensions. * A revised calling convention. * Relaxed stack alignment for soft-float calling convention, and description of the RV32E calling convention. -* A revised proposal for the C compressed extension, version 1.9 . +* A revised proposal for the `C` compressed extension, version 1.9 . *_Preface to Version 2.0_* @@ -312,45 +312,45 @@ extensions. encoding more efficient. * The base ISA has been defined to have a little-endian memory system, with big-endian or bi-endian as non-standard variants. -* Load-Reserved/Store-Conditional (LR/SC) instructions have been added +* Load-Reserved/Store-Conditional (`LR/SC`) instructions have been added in the atomic instruction extension. -* AMOs and LR/SC can support the release consistency model. -* The FENCE instruction provides finer-grain memory and I/O orderings. -* An AMO for fetch-and-XOR (AMOXOR) has been added, and the encoding for -AMOSWAP has been changed to make room. -* The AUIPC instruction, which adds a 20-bit upper immediate to the PC, -replaces the RDNPC instruction, which only read the current PC value. +* `AMOs` and `LR/SC` can support the release consistency model. +* The `FENCE` instruction provides finer-grain memory and I/O orderings. +* An `AMO` for fetch-and-`XOR` (`AMOXOR`) has been added, and the encoding for +`AMOSWAP` has been changed to make room. +* The `AUIPC` instruction, which adds a 20-bit upper immediate to the `PC`, +replaces the `RDNPC` instruction, which only read the current `PC` value. This results in significant savings for position-independent code. -* The JAL instruction has now moved to the U-Type format with an -explicit destination register, and the J instruction has been dropped -being replaced by JAL with _rd_='x0'. This removes the only instruction -with an implicit destination register and removes the J-Type instruction -format from the base ISA. There is an accompanying reduction in JAL +* The `JAL` instruction has now moved to the `U-Type` format with an +explicit destination register, and the `J` instruction has been dropped +being replaced by `JAL` with _rd_=`x0`. This removes the only instruction +with an implicit destination register and removes the `J-Type` instruction +format from the base ISA. There is an accompanying reduction in `JAL` reach, but a significant reduction in base ISA complexity. -* The static hints on the JALR instruction have been dropped. The hints +* The static hints on the `JALR` instruction have been dropped. The hints are redundant with the _rd_ and _rs1_ register specifiers for code compliant with the standard calling convention. -* The JALR instruction now clears the lowest bit of the calculated +* The `JALR` instruction now clears the lowest bit of the calculated target address, to simplify hardware and to allow auxiliary information to be stored in function pointers. -* The MFTX.S and MFTX.D instructions have been renamed to FMV.X.S and -FMV.X.D, respectively. Similarly, MXTF.S and MXTF.D instructions have -been renamed to FMV.S.X and FMV.D.X, respectively. -* The MFFSR and MTFSR instructions have been renamed to FRCSR and FSCSR, -respectively. FRRM, FSRM, FRFLAGS, and FSFLAGS instructions have been +* The `MFTX.S` and `MFTX.D` instructions have been renamed to `FMV.X.S` and +`FMV.X.D`, respectively. Similarly, `MXTF.S` and `MXTF.D` instructions have +been renamed to `FMV.S.X` and `FMV.D.X`, respectively. +* The `MFFSR` and `MTFSR` instructions have been renamed to `FRCSR` and `FSCSR`, +respectively. `FRRM`, `FSRM`, `FRFLAGS`, and `FSFLAGS` instructions have been added to individually access the rounding mode and exception flags -subfields of the 'fcsr'. -* The FMV.X.S and FMV.X.D instructions now source their operands from +subfields of the `fcsr`. +* The `FMV.X.S` and `FMV.X.D` instructions now source their operands from _rs1_, instead of _rs2_. This change simplifies datapath design. -* FCLASS.S and FCLASS.D floating-point classify instructions have been +* `FCLASS.S` and `FCLASS.D` floating-point classify instructions have been added. * A simpler NaN generation and propagation scheme has been adopted. -* For RV32I, the system performance counters have been extended to +* For `RV32I`, the system performance counters have been extended to 64-bits wide, with separate read access to the upper and lower 32 bits. -* Canonical NOP and MV encodings have been defined. +* Canonical `NOP` and `MV` encodings have been defined. * Standard instruction-length encodings have been defined for 48-bit, 64-bit, and latexmath:[$>$]64-bit instructions. -* Description of a 128-bit address space variant, RV128, has been added. +* Description of a 128-bit address space variant, `RV128`, has been added. * Major opcodes in the 32-bit base instruction format have been allocated for user-defined custom extensions. * A typographical error that suggested that stores source their data |